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Digital Camera Patent Abstract
A digital camera, a file output method, a file output program, and
an image data structure for shortening the time required for displaying
the frequency distribution of gray scale levels of a subject image
are provided. A digital camera characterized by an image capturing
unit converting a subject image into image data; a storage unit
storing the subject image as the image data output from the image
capturing unit; a count unit counting the frequency of gray scale
levels of the subject image stored in the storage unit for each
predetermined section; and an output unit storing the subject image
stored in the storage unit and the frequency for each predetermined
section counted by the count unit in one file and outputting the
file.
Digital Camera Patent Claims
10. A digital camera comprising: an image capturing unit converting
a subject image into image data; a storage unit storing the subject
image as the image data output from the image capturing unit; a
count unit counting frequency of gray scale levels of the subject
image stored in the storage unit for each predetermined section;
and an output unit storing the subject image stored in the storage
unit and the frequency for each predetermined section counted by
the count unit in one file and outputting the file.
11. The digital camera as set forth in claim 10, wherein the count
unit counts the frequency for each of sections set at equal intervals
on a logarithmic scale.
12. The digital camera as set forth in claim 10, wherein the count
unit counts the frequency for each of sections set at equal intervals
on a linear scale.
13. The digital camera as set forth in claim 12, wherein the count
unit converts the frequency counted for each of the sections set
at equal intervals on the linear scale into the frequency for each
of the sections set at equal intervals on a logarithmic scale, and
the output unit stores the converted frequency in the file.
14. A file output method comprising: an image capturing step of
converting a subject image into image data; a storage step of storing
the subject image as the image data output in the image capturing
step; a count step of counting frequency of gray scale levels of
the subject image stored in the storage step for each predetermined
section; and an output step of storing the subject image stored
in the storage step and the frequency for each predetermined section
counted in the count step in one file and outputting the file.
15. A file output program causing a digital camera to function
as: an image capturing unit converting a subject image into image
data; a storage unit storing the subject image as the image data
output from the image capturing unit; a count unit counting frequency
of gray scale levels of the subject image stored in the storage
unit for each predetermined section; and an output unit storing
the subject image stored in the storage unit and the frequency for
each predetermined section counted by the count unit in one file
and outputting the file.
16. An image data structure comprising a structure in which image
data representing a subject image and frequency of gray scale levels
of the subject image represented by the image data for each predetermined
section are included in one file.
17. An image quality display comprising: an input unit inputting
a file; and a display unit displaying based on the file that is
input by the input unit and includes image data representing a subject
image and frequency of gray scale levels of the subject image for
each predetermined section in one file, a graph representing the
subject image and the frequency of gray scale levels of the subject
image.
18. The image quality display as set forth in claim 17, wherein
the frequency counted for each of sections set at equal intervals
on a linear scale is converted into the frequency for each of sections
set at equal intervals on a logarithmic scale and the graph representing
the frequency for each of the sections set at equal intervals on
the logarithmic scale is displayed.
Digital Camera Patent Description
TECHNICAL FIELD
[0001] This invention relates to a digital camera, a file output
method, a file output program, an image data structure, and an image
quality display.
BACKGROUND ART
[0002] Hitherto, a digital camera for displaying the frequency
distribution of gray scale levels of an image such as brightness
values and pixel values of RGB channels on a graph such as a histogram
has been known (for example, refer to patent document 1).
[0003] When a subject image to be graphed is selected, an electronic
still camera (digital camera) described in patent document 1 counts
the frequency of gray scale levels for each of sections set at equal
intervals on a linear scale and displays the frequency distribution
of gray scale levels by arranging bars each representing the frequency
in each section by height at equal intervals in a lateral direction.
Such a graph enables the user to check whether or not the exposure
condition when recording a subject image with the digital cameral
is appropriate, for example.
[0004] However, the digital camera described in patent document
1 counts the frequency after a subject image is selected and therefore
it takes a time until a graph is displayed from selection of the
subject image; this is a problem.
[0005] By the way, it is said that the whole senses of a human
being comply with Weber's law and it is said that the sense concerning
the brightness having a correlation with the gray scale level of
an image also complies with Weber's law. According to Weber-Fechner's
law as a development of Weber's law, the relationship between the
sense magnitude and the physical stimulus quantity is represented
by the following expression:S=k.times.log I+c
[0006] Here, S is the sense magnitude, I is the physical stimulus
quantity, and k and c are constants. From the expression, it is
seen that the sense of a human being concerning the brightness can
be approximated by a logarithmic function.
[0007] The exposure value (EV) representing an exposure condition
is defined according to the following expression:2.sup.EV=F.sup.2/t
[0008] Here, F is the F-stop number representing the aperture of
a camera and t is the exposure time (units:Seconds). As shown in
the expression, it is seen that the exposure value is shown by a
logarithmic function. Generally, a large number of subjects concentrate
in the range in which the exposure difference is 5 EV and it is
said that appropriate gradation representation of a subject is made
possible by adjusting the exposure condition so that the brightness
values are distributed in the range corresponding to .+-.2.5 EV
centering on the brightness value corresponding to 18% reflected
light. The exposure value is represented by a logarithmic function
as described above and a general camera is designed so that each
of the lens aperture and the exposure time determining the exposure
value can be changed in 1-EV units, 1/2-EV units, or 1/3-EV units.
[0009] Thus, if the brightness values of an image are displayed
on a histogram with the section axis on a linear scale, it is difficult
for the user to adjust the exposure condition by intuition based
on the histogram; this is a problem. That is, the exposure condition
can be recognized from the histogram of the brightness values with
the section axis on the linear scale, but such a histogram is hard
to use as an index used for exposure correction. More specifically,
if the histogram of the brightness values with the section axis
on the linear scale is displayed, it is difficult for the user to
know how the distribution of the brightness values of the image
representing the subject corresponds to the range in which the exposure
difference is 5 EV and thus it is also difficult for the user to
determine whether or not an image is picked up on appropriate exposure
and further it is also extremely difficult for the user to determine
whether to make 1/3 EV plus correction or 2/3 EV minus correction
to obtain appropriate exposure. For example, the histogram with
the section axis on the linear scale changes in shape before and
after the exposure condition is adjusted in EV units as shown in
FIGS. 16(A) and 16(B) and thus it is difficult for the user to predict
the shape after adjustment before adjustment of the exposure condition.
(FIGS. 16(A) and 16(B) are histograms provided when an image of
the same subject is picked up with the exposure condition adjusted
in EV units in the same image capturing environment.) Therefore,
it is difficult for the user to determine whether or not the brightness
values are distributed appropriately in the range corresponding
to the exposure difference 5 EV by seeing the histograms of FIGS.
16(A) and 16(B) and know how much the exposure value is to be adjusted
in EV units to obtain an optimum brightness value distribution by
intuition. Therefore, it is desirable that a graph representing
the frequency distribution of gray scale levels should be displayed
so that the exposure value can be adjusted by intuition.
[0010] Patent document 1: JP-A-2001-268400
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0011] The invention is created in consideration of the problems
and it is a first object of the invention to provide a digital camera,
a file output method, a file output program, and an image data structure
for shortening the time required for displaying the frequency distribution
of gray scale levels of a subject image.
[0012] It is a second object of the invention to provide an image
quality display for displaying the frequency distribution of gray
scale levels of a subject image in a short time.
Means For Solving the Problems
[0013] To accomplish the first object described above, a digital
camera includes image capturing means for converting a subject image
into image data; storage means for storing the subject image as
the image data output from the image capturing means; count means
for counting frequency of gray scale levels of the subject image
stored in the storage means for each predetermined section; and
output means for storing the subject image stored in the storage
means and the frequency for each predetermined section counted by
the countmeans in one file and outputting the file. If the subject
image and the frequency of gray scale levels of the subject image
counted for each predetermined section are stored in one file, when
a graph representing the frequency distribution of gray scale levels
of the subject image is displayed, the frequency for each section
is read from the file, whereby the time required until the graph
is displayed can be shortened. Thus, the digital camera makes it
possible to shorten the time required for displaying the frequency
distribution of gray scale levels of the subject image.
[0014] To accomplish the first object described above, the count
means of the digital camera counts the frequency for each of sections
set at equal intervals on a logarithmic scale. The digital camera
can display a graph representing the frequency for each of the sections
set at equal intervals on the logarithmic scale. If a graph representing
the frequency for each of the sections set at equal intervals on
the logarithmic scale is displayed, the user can adjust the exposure
condition through intuition. Thus, the digital camera makes it possible
to shorten the time required for displaying the frequency distribution
for enabling the user to adjust the exposure condition through intuition.
[0015] To accomplish the first object described above, the count
means of the digital camera counts the frequency for each of sections
set at equal intervals on a linear scale. The digital camera makes
it possible to display a graph representing the frequency for each
of the sections set at equal intervals on the logarithmic scale
and to display a graph representing the frequency for each of the
sections set at equal intervals on the linear scale.
[0016] To accomplish the first object described above, the count
means of the digital camera converts the frequency counted for each
of the sections set at equal intervals on the linear scale into
the frequency for each of the sections set at equal intervals on
a logarithmic scale, and the output means stores the converted frequency
in the file.
[0017] To accomplish the first object described above, a file output
method includes an image capturing step of converting a subject
image into image data; a storage step of storing the subject image
as the image data output in the image capturing step; a count step
of counting frequency of gray scale levels of the subject image
stored in the storage step for each predetermined section; and an
output step of storing the subject image stored in the storage step
and the frequency for each predetermined section counted in the
count step in one file and outputting the file. The file output
method makes it possible to shorten the time required for displaying
the frequency distribution of gray scale levels of the subject image.
[0018] To accomplish the first object described above, a file output
program causes a digital camera to function as image capturing means
for converting a subject image into image data; storage means for
storing the subject image as the image data output from the image
capturing means; countmeans for counting frequency of gray scale
levels of the subject image stored in the storage means for each
predetermined section; and output means for storing the subject
image stored in the storage means and the frequency for each predetermined
section counted by the countmeans in one file and outputting the
file. The file output program makes it possible to shorten the time
required for displaying the frequency distribution of gray scale
levels of the subject image.
[0019] To accomplish the first object described above, an image
data structure is a structure in which image data representing a
subject image and frequency of gray scale levels of the subject
image represented by the image data for each predetermined section
are included in one file. The image data structure makes it possible
to shorten the time required for displaying the frequency distribution
of gray scale levels of the subject image.
[0020] To accomplish the second object described above, an image
quality display includes input means for inputting a file; and display
means for displaying based on the file that is input by the input
means and includes image data representing a subject image and the
frequency of gray scale levels of the subject image for each predetermined
section in one file, a graph representing the subject image and
the frequency of gray scale levels of the subject image. According
to the image quality display, the graph is displayed based on the
frequency of gray scale levels of the subject image counted for
each predetermined section, so that the frequency distribution of
gray scale levels of the subject image can be displayed in a short
time.
[0021] To accomplish the second object described above, in the
image quality display, the frequency counted for each of sections
set at equal intervals on a linear scale is converted into the frequency
for each of sections set at equal intervals on a logarithmic scale
and the graph representing the frequency for each of the sections
set at equal intervals on the logarithmic scale is displayed.
BEST MODE FOR CARRYING OUT THE INVENTION
[0022] The best mode for carrying out the invention will be discussed
below based on embodiments.
First Embodiment
[0023] FIG. 2 is a block diagram to show the hardware configuration
of a digital still camera (DSC) 1 as a digital camera and an image
quality display according to a first embodiment of the invention.
[0024] An optical system 11 is made up of a plurality of lenses
11a, apertures 11b, etc. The optical system 11 forms a subject image
on the light reception face of an image sensor 12.
[0025] The image sensor 12 is an image capturing device including
photoelectric conversion elements placed discretely in a two-dimensional
space and charge transfer device such as CCD (charge coupled device),
and is a so-called CCD image sensor, CMOS image sensor, etc. The
image sensor 12 is driven by a sensor controller not shown. The
image sensor 12 stores charges provided by performing photoelectric
conversion of the subject image formed on the light reception face
by the optical system 11 for a given time for each photoelectric
conversion element, and outputs an electric signal responsive to
the light reception amount for each photoelectric conversion element.
The image sensor 12 can be provided on the light reception face
with four color filters of C (Cyan), M (Magenta), Y (Yellow), and
G (Green) or three color filters of R (Red), G (Green), and B (Blue)
for inputting color image information. The exposure amount of the
image sensor 12 is determined by the F-stop number of the aperture
11b and the open time of a mechanical shutter not shown, provided
between the optical system 11 and the image sensor 12. The exposure
time of the image sensor 12 may be adjusted by electrically controlling
the charge storage time of the image sensor 12.
[0026] An analog front end (AFE) section 13 quantizes the electric
signal output from the image sensor 12 to a digital signal by an
AD converter and outputs the digital signal. Specifically, for example,
the AFE section 13 performs CDS (Correlated Double Sampling) processing
of reduction processing of noise contained in the electric signal,
optical black clamp control to reproduce the black level of an image,
level adjustment processing of the electric signal by adjusting
the gain of the electric signal of the image, quantization processing,
etc., and outputs RAW data to a digital image processing section
14. In a mode of storing an image in a RAW format, the AFE section
13 outputs data provided by simply performing AD conversion of the
output of the image sensor 12 to an external storage section 16
as it is.
[0027] Here, the RAW data refers generally to data provided by
simply digitalizing an electric signal output from an image capturing
device. Unlike JPEG data, a file in the RAW format is not determined
by international standard and the format can be determined as desired.
Digital data into which a CCD output signal is converted by the
AFE section 13 as it is as well as image capturing information occurring
at the image capturing time in the camera, the image size, the number
of bits representing the gray scale level number per pixel, color
filter arrangement information of the sensor, and the like is stored
in the file in the RAW format in the embodiment. The data corresponding
to the sensor output stored in the file in the RAW format (digital
data into which the output signal of the image sensor 12 is simply
converted) is referred to as RAW data in the embodiment. For example,
in JPEG format, the gradation of each channel of Y, Cb, and Cr is
limited to eight bits and thus if an image capturing device captures
a color tone in 12 to 16 bits, for example, the color tone cannot
perfectly be reproduced and because of irreversible compression,
degradation of the image quality cannot be avoided. The gradation
limitation of eight bits is not placed on the RAW data and the RAW
data need not be irreversibly compressed either. Thus, an image
is stored in the RAW data, whereby the image can be stored without
decreasing the information amount. The RAW data is not limited to
the data output from the AFE section 13 and may be data subjected
to a part of processing performed by the digital image processing
section 14, for example. A scaled-down image in the JPEG format
may be attached to a file in the RAW format. Although the RAW data
cannot be displayed unless image formation processing is performed,
for example, if the DSC 1 reads the scaled-down image in the JPEG
format attached to the RAW data, it is made possible for the DSC
1 to display the object represented by the RAW data at high speed.
[0028] The digital image processing section 14 performs image formation
processing, white balance correction, gamma correction, color space
conversion of converting from RGB color space to YCbCr color space,
and the like for the RAW data output from the AFE section 13 and
then outputs image data represented in the YCbCr color space. Here,
the image formation processing refers to, for example, processing
of forming a color image having gray scale levels of three primary
colors of R, G, and B for each pixel by interpolating the gray scale
level of each pixel acquired in only one color based on the stored
charges of each photoelectric conversion element for receiving light
passing through a specific color filter with nearby pixels.
[0029] The digital image processing section 14 includes an image
scaling-down section 21. The image scaling-down section 21 scales
down an image and outputs the scaled-down image (hereinafter, referred
to as scaled-down image). The image size of the scaled-down image
is set by a control section 20. For example, to display an image
stored in removable memory 17 on a screen of an LCD 18a (see FIG.
3(A)), the image scaling-down section 21 scales down the image to
the screen size of the LCD 18a. Of course, the image scaling-down
section 21 can also scale down the image to any other size. The
scaled-down image generated by the image scaling-down section 21
is output to the removable memory 17 in association with the original
image by the external storage section 16. The image scaling-down
processing may be executed by a program executed in a CPU 20a.
[0030] A compression and decompression section 15 compresses the
image data output from the digital image processing section 14 and
decompresses the compressed image data. The compression and decompression
section 15 specifically compresses the image using the JPEG format
of an irreversible compression method or a reversible compression
method not involving discard of data, for example. The compression
and decompression section 15 is also configured so as to be able
to convert the image data into image data in a TIFF format not performing
compression. In the image storing mode in the RAW format, the compression
and decompression section 15 may perform no operation or may reversibly
compress the RAW data. In the description of the embodiment to follow,
the compression and decompression section 15 performs compression
and decompression processing complying with the JPEG standard.
[0031] The external storage section 16 includes a card slot for
connecting the removable memory 17 as storage means, a memory controller,
and the like. The external storage section 16 is controlled by the
control section 20 and performs processing of writing the image
data compressed by the compression and decompression section 15,
the RAW data output from the AFE section 13, etc., into the removable
memory 17 and processing of reading the data stored in the removable
memory 17.
[0032] A display section 18 includes the LCD (Liquid Crystal Display)
18a, a display controller for controlling the LCD 18a, and the like.
The display section 18 is controlled by the control section 20 and
displays various menus, images, graphs, etc., on the screen of the
LCD 18a. In a playback mode, the display section 18 displays the
primary image or the scaled-down image generated by the image scaling-down
section 21 on the screen of the LCD 18a based on the image data
read from the removable memory 17 by the external storage section
16 and decompressed by the compression and decompression section
15.
[0033] An operation section 19 includes a shutter button, a dial
switch to set an exposure condition and other various image capturing
conditions, a plurality of push-button switches to operate various
displayed menus, a jog dial, and the like.
[0034] The control section 20 includes the CPU 20a, flash memory
20b, and RAM 20c as storage means. The CPU 20a executes a computer
program stored in the flash memory 20b, thereby controlling the
whole DSC 1. The CPU 20a executes a file output program stored in
the flash memory 20b, thereby functioning as image capturing means,
storage means, countmeans, and output means, and executes an image
quality display program, thereby functioning as input means and
display means. The various programs and data stored in the flash
memory 20b may be down loaded from a predetermined sever through
a network for storage or may be read from a computer-readable storage
medium such as removable memory for storage. The RAM 20c is memory
for temporarily storing various programs and data.
[0035] In the embodiment, "image capturing means" as
claimed in Claims corresponds to the optical system 11, the image
sensor 12, the AFE section 13, the digital image processing section
14, and the control section 20. "Output means" as claimed
in Claims corresponds to the external storage section 16 and the
control section 20. "Input means" as claimed in Claims
corresponds to the external storage section 16 and the control section
20. "Display means" as claimed in Claims corresponds to
the display section 18 and the control section 20.
[0036] Next, the appearance of the DSC 1 will be discussed.
[0037] FIG. 3(A) is a rear view of the DSC 1 and FIG. 3(B) is a
top view of the DSC 1 from a Z direction shown in FIG. 3(A).
[0038] An optical finder 30 is provided for the user to visually
check a subject.
[0039] A switch 31, a cocking lever 32, a dial switch 33, a shutter
button 34, a rotary dial 35a, a jog dial 37, a display switch 38,
a menu switch 39, an enter switch 40, and a cancel switch 41 make
up the operation section 19.
[0040] The switch 31 is a power switch. The cocking lever 32 is
provided for performing operation to cock a shutter screen with
a shutter mechanically released so as to allow the next shutter
operation and mechanically fix the shutter. The user cocks the cocking
lever 32 for shutter charge before image capturing, thereby placing
the mechanical shutter in an image capturing operation enable state.
The dial switch 33 is a rotary switch to select and set the shutter
speed, the type of image capturing condition, etc. The shutter button
34 is disposed at the center of the dial switch 33. As the user
pushes the shutter button 34, image capturing operation is started.
[0041] The outer periphery of a needle-type display section 35
installed adjacent to the dial switch 33 is the rotary dial 35a
for enabling the user to adjust the exposure value in 1/3 EV steps
in the range of -2 EV to +2 EV. The remaining number of images that
can be picked up is displayed in a fixed ring 35b provided inside
the rotary dial. White balance, data format, and battery remaining
amount gradations representing the battery remaining amount are
expressed on a dial plate 35c provided inside the fixed ring 35b.
The data format specifically is expressed by a letter R representing
the RAW format, a letter T representing the TIFF format, a letter
H representing the JPEG format in high compression rate, and a letter
N representing the JPEG format in low compression rate. The currently
selected items and the battery remaining amount are indicated by
needles 35d, 35e, and 35f. The user can change the selected item
by rotating the jog dial 37 for moving the needle while operating
a lever switch 36.
[0042] The jog dial 37 is provided so that it can rotate in XY
directions and can move in the axial direction of the rotation axis.
The jog dial 37 is provided so that it can rotate at two positions
in the axial direction. In the description to follow, the position
of the jog dial near to a cabinet 10 of the DSC 1 is called the
lower position and the position where the jog dial 37 is lifted
up from the lower position is called the upper position. In FIG.
3(A), the jog dial 37 at the lower position is indicated by the
solid line and the jog dial 37 at the upper position is indicated
by the dashed line. The user uses the switches and the jog dial
37 in combination to make various settings and select functions.
[0043] The display switch 38, the menu switch 39, the enter switch
40, and the cancel switch 41 are installed to the right of the LCD
18a.
[0044] Next, the file output program will be discussed.
[0045] FIG. 4 is a block diagram to show the logical configuration
of the file output program. The arrow indicated by the solid line
in the figure means a flow of data and the arrow indicated by the
dashed line points to a controlled object. The file output program
includes an image capturing section 51 for causing the DSC 1 to
function as image capturing means, a count section 52 for causing
the DSC 1 to function as count means, and an output section 53 for
causing the DSC 1 to function as output means.
[0046] The image capturing section 51 converts a subject image
into image data. The image capturing section 51 controls the sections
of the DSC 1, converts a subject image into image data, and stores
the provided image data in the RAM 20c.
[0047] The count section 52 counts the frequency of gray scale
levels of the subject image represented by the image data stored
in the RAM 20c for each of sections set at equal intervals on a
linear scale. In the description to follow, the counted frequency
is called graph data. In the description to follow, the subject
image represented by the image data is called simply image.
[0048] FIG. 5 is a schematic drawing to show an example of an image
scanned to create graph data. In the description of the first embodiment,
image data in the JPEG format is taken as an example. The image
data in the JPEG format is image data represented in the YCbCr color
space, and each pixel 61 is made up of three gradation values representing
the gray scale levels of the channels of Y (brightness component),
Cb (bluish component), and Cr (reddish component). In the embodiment,
to represent a histogram of the gray scale levels of the brightness
components of the pixels, the count section 52 counts a frequency
distribution of the brightness components of an image. In the Description,
the gray scale level represented by the brightness component is
called the brightness value. The count section 52 may count a frequency
distribution of the gray scale levels of the image represented by
the gradation values of RGB about each gradation value of R, G,
or B. Only the pixel values of a specific channel may be counted
in such a manner that only the pixel values of the G channel are
counted, for example.
[0049] In the first embodiment, to shorten the data creation time,
the count section 52 creates graph data based on a scaled-down image.
Frequency count in each section is conducted based on the scaled-down
image, whereby the time required for processing to create graph
data is shortened as compared with the case where frequency count
is conducted based on the image before being scaled down.
[0050] Graph data may be created based on the primary image or
may be created based on the image scaled down matching the display
screen size for easy display in the screen size of the LCD 18a.
Graph data may be created based on the image provided by scaling
down the primary image to a different size from the primary image
or the display image. Specifically, for example, graph data may
be created based on the 3008.times.2000 primary image, may be created
based on the scaled-down image provided by scaling down the primary
image to a size of 640.times.425 as an easy-to-display size in the
screen size of the LCD 18a, or may be created based on the 376.times.250
scaled-down image provided by scaling down the primary image to
1/8 in an up and down direction and to 1/8 from side to side. If
the scaling-down rate is appropriate, the histogram displayed based
on the graph data created based on the scaled-down image and the
histogram displayed based on the graph data created based on the
primary image almost match in shape, so that the count section 52
creates the graph data based on the scaled-down image, whereby graph
data creation processing can be speeded up without impairing the
function of the displayed histogram.
[0051] The count section 52 sets sections at equal intervals on
a logarithmic scale and counts the frequency distribution of the
brightness values of the image. A count table 65 shown in FIG. 6
is a table for associating the sections of a histogram set at equal
intervals on the logarithmic scale and the brightness values of
an image represented on the linear scale with each other. The section
representative value of the logarithmic scale and the section range
of the linear scale are set on each row of the count table 65. In
the count table 65, the brightness value of the linear scale (x)
and the brightness value of the logarithmic scale (EV) are associated
with each other according to the relation of the following expression:EV=Log.sub.2
(x/255)
[0052] In the count table 65, the sections are set in the range
of 0.0 to -8.2 on the logarithmic scale. 0.0 of the logarithmic
scale corresponds to the maximum brightness value, and -8.2 of the
logarithmic scale corresponds to the minimum brightness, value.
The minimum value 0 of the brightness value of the 8-bit linear
scale is -.infin. if it is represented on the logarithmic scale
using the expression shown above. The minimum brightness value in
the section with the representative value -8.2 is set to -.infin.
on the logarithmic scale. How much the minimum section of the EV
scale is to be set low is a design item that can be determined in
response to how much detail the frequency distribution in the low
range of the brightness values is to be displayed.
[0053] The section representative value is a convenient value to
show the relative exposure difference between the sections, and
whether or not the representative value of the maximum section is
represented as 0.0 is a design item that can be selected appropriately.
For example, the brightness values 0 to 255 on the linear scale
may be associated with the sections set in the range of 4.0 to -4.2
on the logarithmic scale. In the count table 65, the width of each
section is set to 0.2 EV equivalent, but how the width of each section
is to be set is a design item that can be selected appropriately.
For example, the section width may be 1/10 EV or 1/20 EV, may be
1/3 EV, may be 1/6 EV,may be 1/9 EV, or may be furthermore fine
1/30 EV. Further, the section widths may be appropriate intervals
such that the displayed histogram is seen so as to distribute more
finely and smoothly.
[0054] FIG. 6 also shows the width of the range of the brightness
values on the linear scale for each section where frequency count
is conducted, namely, the section width. For example, for the section
with the representative value -0.2 on the logarithmic scale, the
brightness values of the linear scale corresponding to the section
are 222 to 254 and therefore the section width is 33. If the sections
of the brightness values are set at equal intervals on the logarithmic
scale, consequently the correlation between the width of the linear
scale of each section and the section representative value of the
logarithmic scale can be appropriated according to a predetermined
exponential function. Specifically, the larger the section representative
value of the logarithmic scale, the wider the section width of the
linear scale in accordance with the predetermined exponential function.
[0055] A count table shown in FIG. 17 is an example in which the
sections are set more finely than the count table 65 in FIG. 6.
To display a histogram finer than the histogram displayed according
to the graph data created based on the count table 65 in FIG. 6,
the sections may be set finely. For example, in section setting
at intervals of 0.02 on the logarithmic scale with the base 2 as
shown in FIG. 17, about 400 sections are set in the range of width
8 EV and thus a considerably fine histogram can be displayed. How
much detailed histogram is to be displayed on the screen is a design
item that can be selected appropriately. Generally, to display a
histogram in the range of width 8 EV, a sufficiently fine histogram
can be displayed if no less than 200 sections exist. For example,
if the sections are set at intervals of 0.04 on the logarithmic
scale with the base 2, a considerably fine histogram can be displayed.
In the description of the embodiment, the brightness value is represented
on the 8-bit linear scale, but the brightness value of the linear
scale can be represented in any other number of bits such as 10
bits or 12 bits, of course. The association of the brightness value
of the logarithmic scale (EV) and the brightness value of the linear
scale (x) with each other is EV=Log.sub.2 (x/1023) if the brightness
value of the linear scale is 10-bit representation or is EV=Log.sub.2
(x/4095) if the brightness value of the linear scale is 12-bit representation.
As described above, the base of the logarithm is set to 2, whereby
the scale of the exposure value and the scale of the brightness
value can be matched with each other.
[0056] The count section 52 initializes the frequency of each section
to 0 and then references the count table 65 about the brightness
value of each of the pixels making up the scaled-down image to determine
the section to which the pixel belongs, and adds one to the frequency
of the determined section, thereby counting the frequency. The frequencies
thus counted about all sections are output to the output section
53 as graph data.
[0057] The frequency may be counted in a given section width on
the linear scale before the count table 65 is referenced instead
of referencing the count table 65 for each pixel to determine the
section to which the pixel belongs. Specifically, for example, for
the image made up of pixels having the brightness values of 256-step
gradation from 0 to 255 on the linear scale, the frequency distribution
of the brightness values is found with the section width of each
section set to 1 on the linear scale. Here, the section whose section
width is 1 on the linear scale is called primary section and the
sections set at equal intervals on the logarithmic scale are called
secondary sections. Next, while the count table 65 is referenced,
the secondary sections corresponding to all primary sections are
determined and the frequency of the primary section where the corresponding
secondary section becomes the same is counted and the counted frequency
is adopted as the frequency of the secondary section. Finding the
frequency distribution of the brightness values of the linear scale
with all sections set to a given width on the linear scale is also
performed formerly, so that a circuit or a program in a related
art can be used for the processing of finding the frequency distribution
of the brightness values of the linear scale with all sections set
to the given width on the linear scale.
[0058] Frequency count may be conducted for the image subjected
to gamma correction or may be conducted for the image not subjected
to gamma correction. For a general image with gamma of 1/2.2, the
relation between the brightness value Y of the image after being
subjected to gamma correction and the brightness value X of the
image before being subjected to gamma correction is represented
by the following expression:Y=X.sup.1/2.2
[0059] Therefore, the brightness value EV of the logarithmic scale
of the image after being subjected to gamma correction is represented
by the following expression:EV=Log.sub.2 Y=Log.sub.2 X.sup.1/2.2=(1/2.2).times.Log.sub.2
X
[0060] Therefore, the histogram displayed according to the graph
data created based on the gamma-corrected image is displayed in
the form in which it is compressed in the section axial direction
by gamma value. For example, to display the histogram so that the
brightness values of the image before being subjected to gamma correction
are distributed to sections from -8 EV to 0 EV, the brightness values
of the image after being subjected to gamma correction with gamma
set to 1/2.2 are distributed to sections from -3.64 EV to 0 EV.
For example, to display the histogram so that the brightness values
of the image before being subjected to gamma correction are distributed
to sections from -5 EV to 0 EV, the brightness values of the image
after being subjected to gamma correction with gamma set to 1/2.2
are distributed to sections from -2.27 EV to 0 EV.
[0061] The output section 53 stores the image stored in the RAM
20 by the image capturing section 51 and the frequency for each
of the sections set at equal intervals on the logarithmic scale,
counted by the count section 52, namely, graph data in one file
and outputs the file. Specifically, the output section 53 controls
the external storage section 16 to create a file in the removable
memory 17 and writes image data representing an image and the graph
data of the image into the created file. The DSC 1 may be provided
with a network interface through which the output section 53 transmits
a file to another apparatus for outputting the file. In the description
to follow, the output file is called image file.
[0062] FIG. 1 is a schematic drawing to show the structure of an
image file. The image file is made up of a header area 55, an image
data area 56, and a graph data area 57. The header area 55 is an
area to record header information of the creation date, the image
size, a pointer pointing to the top address of the image data area
56, a pointer pointing to the top address of the graph data area
57, etc. The image data area 56 is an area to record the image data
representing the image. The image data may be recorded in the JPEG
format or may be recorded in the TIFF format, the bit map format,
etc., for example. The graph data area 57 is an area to record the
graph data. In the graph data area 57 shown in the figure, the frequencies
of the sections are separated by a comma for storage in order from
the frequency of the section determined by the section representative
value "-8.2." To play back, the pointers are read from
the header area, whereby the top address of the image data area
and the top address of the graph data area can be determined and
accordingly the image data and the graph data can be read. Here,
the method of storing the histogram frequencies on the logarithmic
scale in the file is shown, but the stored frequency data may be
the histogram frequencies on the linear scale.
[0063] Next, a processing flow of outputting an image file by the
DSC 1 will be discussed.
[0064] FIG. 7 is a flowchart to show the processing flow of outputting
an image file by the DSC 1.
[0065] At S105, the DSC 1 converts a subject image into image data.
Specifically, the image capturing section 51 controls the sections
of the DSC 1 and converts the subject image into image data. When
converting the subject image into image data, the image capturing
section 51 stores the provided image data in the RAM 20c.
[0066] At S110, the image scaling-down section 21 scales down the
stored image to generate image data of the scaled-down image.
[0067] At S115, the count section 52 counts the frequency of gray
scale levels of the generated scaled-down image for each of the
sections set at equal intervals on the logarithmic scale, and generates
graph data.
[0068] At S120, the output section 53 stores the stored image and
the generated graph data in one file and outputs the file to the
removable memory 17.
[0069] In the processing at S105 to S115, the DSC 1 once scales
down the image and calculates the frequencies of the gray scale
levels about the scaled-down image data, but may directly calculate
the frequencies of the gray scale levels about the original large
image data without scaling down the image. In calculating the frequencies
of the gray scale levels in the processing at S105 to S115, the
frequency may be counted for each of the sections set at equal intervals
on the linear scale instead of counting the frequency for each of
the sections set at equal intervals on the logarithmic scale.
[0070] Next, the image quality display program will be discussed.
[0071] FIG. 8 is a block diagram to show the logical configuration
of the image quality display program. The arrow indicated by the
solid line in the figure means a flow of data and the arrow indicated
by the dashed line points to a controlled object. The image quality
display program includes an input section 63 for causing the DSC
1 to function as input means and a display section 64 for causing
the DSC 1 to function as display means.
[0072] The input section 63 controls the external storage section
16 to read an image file from the removable memory 17 into the RAM
20c. The input section 63 may input an image file by down loading
data from another apparatus through a network interface.
[0073] The display section 64 displays various menus, the image
stored in the removable memory 17, the histogram of the image, etc.,
on the LCD 18a.
[0074] FIG. 9 is a schematic drawing to describe a GUI of the DSC
1. When the power is turned on, the DSC 1 is started and makes a
transition to an image capturing mode. This image capturing mode
is a mode of picking up an image. When the shutter button 34 is
pressed in the image capturing mode, the image capturing section
51 starts the operation of picking up a subject image, performs
various types of processing for the signal output from the image
sensor 12, generates image data representing the subject image,
and stores the generated image data on external memory card 17 through
the external storage section 16. When the display switch 38 is pressed
in the image capturing mode, the DSC 1 makes a transition to a playback
mode.
[0075] The playback mode is a mode of displaying the image stored
in the removable memory 17 on the LCD 18a. When the jog dial 37
is set to the lower position in the playback mode, if the user rotates
the jog dial 37, the image files stored in the removable memory
17 are selected in a predetermined order (75h). When the image file
is selected, the image stored in the selected image file is displayed
on the LCD 18a. The image files are selected in the ascending or
descending order of the image file names containing the consecutive
numbers given to the image files in the image capturing order at
the image capturing time. That is, when the jog dial 37 is rotated
to the right, the images are selected in the image capturing order;
when the jog dial 37 is rotated to the left, the images are selected
in the opposite order to the image capturing order. The images may
be selected in the order of image capturing dates and times rather
than in the order of the image file names.
[0076] In the playback mode, the DSC 1 displays the scaled-down
image, the primary image, or various pieces of attached information
to the primary image stored in the image file selected at the time.
The DSC 1 specifically provides a plurality of playback modes of
standard display 75a, simple information display 75b, histogram
display 75c, highlight display 75d, detailed information display
75e, GUI nondisplay 75f, and 4-division display 75g. When the user
rotates the jog dial 37 at the upper position, the display section
64 displays the scaled-down image, the primary image, or the attached
information in the playback mode responsive to the rotation.
[0077] In a specific playback mode in which a specific image file
is selected, when the jog dial 37 rotates at the lower position,
the image file preceding or following the specific image file is
newly selected and the scaled-down image, the primary image, or
the attached information in the newly selected image file is displayed
in the playback mode intact.
[0078] In the standard display 75a, the scaled-down image or the
primary image and "image number/total number of images"
are displayed. When a specific image file is selected, the display
section 64 may first display the scaled-down image and then display
the primary image. In any other playback mode for displaying images,
likewise, when a specific image file is selected, the display section
64 may first display the scaled-down image and then display the
primary image.
[0079] In the simple information display 75b, the scaled-down image
or the primary image and current "image number/total number
of images," file number, image capturing quality, file protection,
and image capturing date and time are displayed on one screen.
[0080] In the histogram display 75c, the scaled-down image or the
primary image and current "image number/total number of images"
and the histogram created based on the graph data stored in the
selected image file are displayed on one screen. The histogram display
method is described later. In the histogram display 75c, only the
histogram may be displayed on one screen without displaying any
image.
[0081] In the highlight display 75d, a white spot of the scaled-down
image or the primary image is displayed on the scaled-down image.
[0082] In the detailed information display 75e, the scaled-down
image or the primary image and current "image number/total
number of images," file number, image capturing quality, file
protection, image capturing date and time, file number, shutter
speed, white balance (WB), resolution, and film setting are displayed
on one screen.
[0083] In the GUI nondisplay 75f, the scaled-down image or the
primary image is displayed.
[0084] In the 4-division display 75g, the scaled-down images of
the images stored in the four image files with the consecutive file
names are displayed in the four areas into which one screen is divided.
[0085] When the histogram display 75c is selected, the display
section 64 uses the graph data stored in the selected image file
to create a histogram as a graph.
[0086] FIG. 10(A), FIG. 10(B), and FIG. 10(C) are schematic drawings
to show examples of histograms displayed on the LCD 18a by the display
section 64. In the examples shown in FIG. 10(A) and FIG. 10(B),
the frequency of each section is represented by the area of the
rectangle with the section as the bottom. Since the width of each
rectangle with the section as the bottom is fixed, the frequency
of each section is also represented by the height of the rectangle.
In the histogram shown in FIG. 10(C), the frequency of each section
is represented by the height of the polygonal line. The ratio between
the height or the area of each section represented in the histogram
and the frequency of each section can be set as desired.
[0087] It is desirable that the display section 64 should display
gradations of the section axis. Specifically, the gradations are
arranged in the section axial direction, for example, as shown in
FIG. 10(A), FIG. 10(B), and FIG. 10(C). The gradations are arranged
in the section axial direction at interval 1, whereby it is made
possible for the user to easily understand how much the pixel values
of pixels are distributed in the 1-EV unit width, so that exposure
correction is furthermore facilitated. It is desirable that digits
representing the scale of the section axis with the logarithm of
base 2 should be added to the gradations. The gradations and the
digits of the logarithmic scale with the base 2 are added to the
gradations of the section axis, whereby the user can keep track
of the correspondence between the sections and the exposure values
and can easily know how many steps the exposure condition is adjusted
in on the EV scale to set appropriate exposure.
[0088] By the way, generally it is said that the optimum exposure
is the light amount of an object with reflectivity 18%. The exposure
condition such that the average value or the center value as the
representative value of the brightness values of an image corresponds
to the light amount can be a proper exposure condition. Then, it
is desirable that the display section 64 should display a graph
for guiding the section corresponding to the average value of the
brightness values of an image picked up under the proper exposure
condition. A heavy dashed line passing through the section and being
parallel with the longitudinal axis is displayed, for example, as
shown in FIG. 10(A), FIG. 10(B), and FIG. 10(C). The display section
64 sets sections so that the section is positioned at the center
of the horizontal axis and displays a histogram with the center
section representative value set to 0, for example, as shown in
FIG.(B).
[0089] The average value as the representative value of the brightness
values of an image picked up under the proper exposure condition
is set as follows: For example, to record reflected light of 0%
to 100% with the brightness values 0 to 255, the brightness value
corresponding to the reflected light of 18% is 46. Therefore, if
the brightness value x of the linear scale and the brightness value
EV of the logarithmic scale are associated with each other according
to EV=Log.sub.2 (x/255), the section of -2.47 EV (=Log.sub.2 (46/255))
is the section corresponding to the average value of the brightness
values of an image picked up under the proper exposure condition.
To record reflected light of 0% to 120% with the brightness values
0 to 255 with a digital camera for recording to a brighter place,
the brightness value corresponding to the reflected light of 18%
is 38. Therefore, if the brightness value x of the linear scale
and the brightness value EV of the logarithmic scale are associated
with each other according to EV=Log.sub.2 (x/255), the section of
-2.74 EV (=Log.sub.2 (38/255)) is the section corresponding to the
average value of the brightness values of an image picked up under
the proper exposure condition. These are examples where gamma is
1.
[0090] For the image after being subjected to gamma correction
with gamma set to 1/2.2, the representative value of the brightness
values of an image picked up under the proper exposure condition
is calculated as follows: To record reflected light of 0% to 100%
with the brightness values 0 to 255, the brightness value after
gamma correction corresponding to the reflected light of 18% is
118. Therefore, if the brightness value x of the linear scale (before
gamma correction) and the brightness value EV of the logarithmic
scale (after gamma correction) are associated with each other according
to EV=Log.sub.2 (x/255), the section of -1.12 EV (=Log.sub.2 (0.18.sup.1/2.2))
is the section corresponding to the average value of the brightness
values of an image picked up under the proper exposure condition.
It is 1/2.2 times the brightness value before gamma correction,
-2.47 EV. To record reflected light of 0% to 120% with 0 to 255,
according to similar calculation, the section of -1.24 EV, 1/2.2
times -2.74 EV is the section corresponding to the average value
of the brightness values of an image picked up under the proper
exposure condition.
[0091] Gradations of a gray scale rather than the characters representing
the exposure values added to the gradations (-8 EV to 0 EV) maybe
displayed along the horizontal axis. The histogram need not necessarily
show the frequency distribution in the entire range. The histogram
may be displayed in the range of -5 EV to 0 EV based on the frequency
distribution count result from 0.0 EV to -8.2 EV, for example, as
shown in FIG. 18.
[0092] A plurality of dashed lines 70a to 70h as guide indicate
the sections set at equal intervals on the linear scale. For example,
assume that the brightness value range of 0 to 255 is divided into
eight sections each with width 32 at equal intervals. In this case,
for example, the upper limit brightness value in the section of
0 to 31 is 31 and thus the display section 64 displays the dashed
line 70a passing through exposure value "-3.2" EV corresponding
to the brightness value 31 and being parallel with the longitudinal
axis and in the next section, displays the dashed line 70b passing
through exposure value "-2.2" EV corresponding to the
brightness value 63 and being parallel with the longitudinal axis.
In any other section, the display section 64 displays the dashed
line in a similar manner. Therefore, the dashed line indicates the
boundary between the sections set at equal intervals on the linear
scale. That is, a histogram 70 shows the frequency of each of the
sections set at equal intervals on the logarithmic scale as the
area of each rectangle of the histogram and shows the frequency
of each of the sections set at equal intervals on the linear scale
by the sum of the areas of a plurality of rectangles sandwiched
between two dashed lines indicating the boundaries between the sections
set at equal intervals on the linear scale. In the first embodiment,
the boundary between the sections set at equal intervals on the
linear scale is displayed by the dashed line, but at the position
of each dashed line of the horizontal axis, the brightness value
corresponding to the dashed line may be added as digits without
displaying the dashed line. The dashed lines 70a to 70h need not
be displayed if they are not required.
[0093] FIG. 11 is a schematic drawing to show a state in which
a screen on which an image 60 and the histogram 70 are superposed
on each other is displayed on the LCD 18a. In the first embodiment,
the display section 64 displays the background of the histogram
70 transparent, as shown in the figure. Specifically, the display
section 64 displays only the components of the histogram 70 such
as the rectangles indicating frequencies, the longitudinal axis,
the horizontal axis, etc., on the image 60. If such display is produced,
the user can also check the image 60 in the area corresponding to
the background of the histogram 70, so that the area of the image
60 hidden by the histogram 70 can be lessened. The display section
18 may put the background of the histogram 70 on the image 60 without
making the background transparent or may put the rectangles indicating
frequencies on the image with the rectangles made translucent. Preferably,
the display section 64 mixes them at the transmittance of the image
60 as 50% and the transmittance of the histogram 70 as 50% for display
in a translucent state in the rectangle area in which the histogram
70 is displayed.
[0094] Next, a processing flow of displaying an image and a histogram
by the DSC 1 will be discussed.
[0095] FIG. 12 is a flowchart to show the processing flow of displaying
an image and a histogram by the DSC 1.
[0096] At S205, the DSC 1 inputs an image file. Specifically, the
input section 63 reads the image file selected in response to rotation
of the jog dial 37 at the lower position from the removable memory
17.
[0097] At S210, the DSC 1 scales down the image stored in the read
image file to generate image data of the scaled-down image.
[0098] At S215, when the user selects the histogram display 75c,
the DSC 1 superposes the scaled-down image and the histogram on
each other on the LCD 18a, as shown in FIG. 11.
[0099] The DSC 1 according to the first embodiment of the invention
described above stores an image and graph data of the image in one
file. Thus, when displaying a histogram representing the frequency
distribution of the brightness values of an image, the DSC 1 reads
the graph data from the image file, whereby the time required until
the histogram is displayed can be shortened as compared with the
case where the frequencies are counted after a histogram display
command is given. Thus, the DSC 1 makes it possible to shorten the
time required for displaying the frequency distribution of the brightness
values of the image.
[0100] If the image and the graph data are stored in one file,
the portability of the image and the graph data improves as compared
with the case where they are stored in separate files.
[0101] The frequency distribution of the brightness values of the
image is represented by a histogram with the section axis on the
logarithmic scale, whereby the frequency distribution of the brightness
values represented by the histogram and the frequency distribution
of the brightness values perceived by the user as the user sees
the image almost match. Therefore, the frequency distribution shown
by the histogram according to the first embodiment is easy to understand
through intuition in a sense concerning the brightness that the
user seems to perceive when the user sees the image. The image and
the histogram representing the frequency distribution of the brightness
values are displayed on one screen, so that the user can make a
comparison between the histogram and the image on one screen and
can easily understand the meaning indicated by the frequency distribution
represented by the histogram. Thus, the DSC 1 can display the frequency
distribution of the brightness values of the image in an easy-to-understand
manner for the user.
[0102] If a histogram with the section axis on the logarithmic
scale is displayed, when the exposure condition is adjusted and
an image of the same subject is picked up in the same environment
and a histogram is displayed based on the picked-up image, before
and after the exposure condition is adjusted, the histograms move
only to the left or the right and do not change in shape, as shown
in FIG. 13(A) and FIG. 13(B). The fact that the histogram shape
does not change if the exposure condition is changed when an image
of the same subject is picked up is a large advantage provided as
the section axis is the logarithmic scale. Thus, the user can adjust
the exposure condition through intuition so that the brightness
values after adjustment are distributed in a specific range based
on the histogram before adjustment. Therefore, the user can easily
capture an image with the exposure condition appropriately adjusted.
When the user picks up an inappropriate image, the user can understand
through intuition how much the exposure condition is to be adjusted
for picking up an appropriate image.
[0103] Gradations are added to the section axis on the logarithmic
scale with the base 2 and the same scale digits as the exposure
values are added to the gradations, whereby the user can recognize
the sections and the exposure values in direct association with
each other and thus adjustment of the exposure condition is furthermore
facilitated. Specifically, when a proper exposure condition is set
if the histogram is moved in parallel in the section axial direction
by width W on the gradations of the section axis, the user can capture
an image of a subject under the proper exposure condition simply
by adjusting the exposure condition so as to change the exposure
value of the digital camera by W.
[0104] The DSC 1 displays the frequency distribution of the sections
set at equal intervals on the linear scale and the frequency distribution
of the sections set at equal intervals on the logarithmic scale
as one histogram. Thus, the user can check the two frequency distributions
on one histogram. Thus, the DSC 1 can display the frequency distribution
of the sections set at equal intervals on the linear scale and the
frequency distribution in which the exposure value can be adjusted
through intuition in an easy-to-use manner.
[0105] In the first embodiment, the digital camera and the image
quality display have been described by taking the DSC 1 as an example,
but the image quality display may be a personal computer, a PDA,
etc. The digital camera may be a digital video camera, a mobile
telephone with a digital camera, a PDA with a digital camera, etc.
[0106] In the description of the first embodiment, the graph data
is generated based on the image data in the JPEG format by way of
example, but the graph data may be generated based on the RAW data
and the generated graph data and the RAW data may be stored in one
file.
Second Embodiment
[0107] In a second embodiment, the frequency is counted for each
of sections set at equal intervals on a linear scale. Specifically,
for example, a DSC according to the second embodiment counts the
frequency for each brightness value of the linear scale about the
image stored in RAM 20c and sums up the counted frequency for each
brightness value for each of the sections set at equal intervals
on the linear scale. For example, assume that each section width
is 8 on the linear scale and the range of 0 to 255 is divided into
32 sections at equal intervals. In this case, the DSC sums up the
frequencies of the brightness values of 0 to 7 about the first section.
The DSC sums up the frequencies of the brightness values of 8 to
15 about the next section. Similarity also applies to other sections.
Consequently, the frequency for each of the sections at equal intervals
of the width 8 on the linear scale is counted. Of course, for an
image with the brightness value represented in eight bits, the section
width may be 1 on the linear scale and the frequency distribution
of 256 sections of 0 to 255 may be counted.
[0108] In the second embodiment, the DSC displays a histogram on
the LCD 18a based on the graph data counted for each of the sections
set at equal intervals on the linear scale, thereby displaying the
histogram representing the frequency for each of the sections set
at equal intervals on the linear scale.
[0109] FIG. 14 is a schematic drawing to show a histogram of the
second embodiment. In the second embodiment, the DSC displays guide
indicating the sections set at equal intervals on the logarithmic
scale for the histogram displayed based on a frequency distribution
table with the section width fixed on the linear scale, thereby
displaying the frequency distribution with the sections set at equal
intervals on the linear scale and the frequency distribution with
the sections set at equal intervals on the logarithmic scale as
one histogram. Each rectangle corresponds to each of the sections
divided at equal intervals on the linear scale.
[0110] A plurality of dashed lines 80a, 80b, 80c, 80d, and 80e
as guides indicate the sections set at equal intervals on the logarithmic
scale. If the dashed lines 80a, 80b, 80c, 80d, and 80e are shown
with spacing corresponding to 0.2 EV, the number of dashed lines
increases and the dashed lines become hard to see. Thus, in the
second embodiment, the dashed lines 80a, 80b, 80c, 80d, and 80e
are shown with spacing corresponding to 1 EV. Since the spacing
between two of the dashed lines 80a to 80e is 1 on the logarithmic
scale, the dashed lines 80a to 80e guide the user as the sections
each with the width 1 on the logarithmic scale. That is, the user
can recognize the frequency of brightness values for each section
with the width 1 on the logarithmic scale according to the total
sum of the areas of the rectangles sandwiched between the adjacent
dashed lines. The dashed lines 80a to 80e need not be displayed
if they are not required. The second embodiment is substantially
the same as the first embodiment in other points.
Third Embodiment
[0111] In a third embodiment, a histogram representing the frequency
for each of sections set at equal intervals on the logarithmic scale
is displayed based on graph data provided by counting the frequency
for each of sections set at equal intervals on the linear scale.
Specifically, a DSC according to the third embodiment determines
the exposure value corresponding to each of the sections set at
equal intervals on the linear scale by referencing a count table
65, and adds the frequency of the section of the graph data to the
count value of the determined exposure values. Accordingly, the
DSC converts into the frequency for each of the sections set at
equal intervals on the logarithmic scale. After the count, the DSC
displays a histogram representing the frequency for each of the
sections set at equal intervals on the logarithmic scale as in the
first embodiment. To display the histogram representing the frequency
for each of the sections set at equal intervals on the logarithmic
scale based on the graph data provided by counting the frequency
for each of the sections set at equal intervals on the linear scale,
an image is selected before count is executed, and thus the time
for count becomes necessary. However, count needs only to be executed
for 256 pieces of graph data of 0 to 255 and thus count can be executed
in a short time as compared with the case where the section is determined
for each brightness value and the frequency is counted. Therefore,
the time required for displaying the frequency distribution of the
brightness values of an image can be shortened. The third embodiment
is substantially the same as the first embodiment in other points.
The frequency counted for each of the sections set at equal intervals
on the linear scale may be converted into the frequency for each
of the sections set at equal intervals on the logarithmic scale
for storage of the provided frequency in an image file as graph
data.
[0112] As described in the second and third embodiments, if the
frequency for each of the sections set at equal intervals on the
linear scale is counted, the DSC can display the histogram representing
the frequency for each of the sections set at equal intervals on
the linear scale in a short time and can display the histogram representing
the frequency for each of the sections set at equal intervals on
the logarithmic scale in a short time.
Fourth Embodiment
[0113] FIG. 15 is a schematic drawing to display a histogram solely.
A display section in a fourth embodiment displays a histogram solely
as shown in the figure. The fourth embodiment is substantially the
same as the first embodiment in other points. A DSC according to
the fourth embodiment does not superpose the histogram on a scaled-down
image or does not display the histogram and a scaled-down image
side by side and thus can display the histogram largely and in an
easy-to-see manner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0114] FIG. 1 is a schematic drawing to show the structure of an
image file according to a first embodiment of the invention.
[0115] FIG. 2 is a block diagram of a digital camera according
to the first embodiment of the invention.
[0116] FIG. 3(A) is a rear view of the digital camera according
to the first embodiment of the invention and FIG. 3(B) is a top
view of the digital camera.
[0117] FIG. 4 is a block diagram of a file output program according
to the first embodiment of the invention.
[0118] FIG. 5 is a schematic drawing to show an example of a subject
image according to the first embodiment of the invention.
[0119] FIG. 6 is a schematic drawing to show a count table according
to the first embodiment of the invention.
[0120] FIG. 7 is a flowchart to show a processing flow of outputting
a file according to the first embodiment of the invention.
[0121] FIG. 8 is a block diagram of a program for displaying image
quality according to the first embodiment of the invention.
[0122] FIG. 9 is a schematic drawing of a GUI of the digital camera
according to the first embodiment of the invention.
[0123] FIGS. 10(A), (B), and (C) are schematic drawings to show
graphs representing the frequencies of gray scale levels according
to the first embodiment of the invention.
[0124] FIG. 11 is a schematic drawing of a screen of the digital
camera according to the first embodiment of the invention.
[0125] FIG. 12 is a flowchart to show a processing flow of displaying
an image and a graph according to the first embodiment of the invention.
[0126] FIG. 13(A) is a schematic drawing to show a graph before
adjustment of exposure condition and FIG. 13(B) is a schematic drawing
to show a graph after adjustment of exposure condition.
[0127] FIG. 14 is a schematic drawing to show a graph representing
the frequencies of gray scale levels according to the first embodiment
of the invention.
[0128] FIG. 15 is a schematic drawing to show a graph representing
the frequencies of gray scale levels according to a fourth embodiment
of the invention.
[0129] FIGS. 16(A) and(B) are schematic drawings to show graphs
in a related art.
[0130] FIG. 17 is a schematic drawing to show a count table according
to the first embodiment of the invention.
[0131] FIG. 18 is a schematic drawing to show a graph representing
the frequencies of gray scale levels according to embodiment of
the invention.
DESCRIPTION OF REFERENCE NUMERALS
[0132] 1 Digital still camera (digital camera, image quality display),
11 Optical system (image capturing means), 12 Image sensor (image
capturing means), 13 Analog front end section (image capturing means),
14 Digital image processing section (image capturing means), 16
External storage section (output means, input means), 18 Display
section (display means), 20 Control section (image capturing means,
output means, input means, display means), 20a RAM (storage means)
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