色彩/色調

Measure color accuracy, tonal response, and noise from a large variety of test charts

Imatest 2020.1  We have added support for the TE269V2 and V3 Dynamic Range chart, which have the same layout as our 36-patch DR chart, but a different patch order. Reference files are now available.

Introduction

Imatest™ Color/Tone Interactive analyzes images of most popular color and grayscale test charts for color accuracy, tonal response, noise, ISO sensitivity, and Dynamic Range (for transmissive grayscale charts) using a highly interactive user interface. It can be used to measure white balance and color response for a wide range of lighting conditions and scenes. It can also display the tonal response of monochrome charts (or monochrome portions of color charts). A color correction matrix (CCM) can be calculated and used to correct images. The Color/Tone Auto (Multitest) module performs the same analyses using a non-interactive (fixed; batch-capable) interface.
 

The most popular supported test charts are shown in the table below.

A full set of charts and a guide to their use is in
Color/Tone Test Chart Reference & Guide

Colorchecker	IT8.7	Colorchecker SG	36-Patch DR charts	ChromaDuMonde 24+4R
Universal Test Target (UTT)	ISO-15739	Q-13 (linear grayscale)	Contrast Resolution	SpyderCHECKR
ColorGauge (Micro, Nano, etc.)	RezChecker	TE269, TE269V2 or V3 (3 versions)	General mxn charts (L*a*b* reference file required)	ISO-14524
Many other charts are supported, including SFRplus and eSFR ISO color patterns (not automatically detected in Color/Tone), SMPTE/Hale Color Bars (6 patches), and TE226 (9x5) color chart. These charts are described in more detail below; the full set of charts is presented in Color/Tone Test Chart Reference & Guide

Getting started

Color/Tone Interactive Quickstart Photograph the chart, using even glare-free lighting. Color and grayscale chart images usually should not fill the frame (1200 vertical pixels is usually sufficient). Filling the frame can cause light falloff issues. Open Color/Tone Interactive. Select the chart type or (if the type is correct) press Read image file. There are some special chart types. (5.2+) Select the chart to read (color, grayscale, or linear grayscale) in the Chart dropdown menu on the right. (Pre-5.2) For linear grayscale charts (all patches in a row) select 6. Grayscale stepchart (linear). (Pre-5.2) For multi-row grayscale charts (e.g., ISO 15739, ISO 14524, Imatest Dynamic Range charts), select 7. Multi-row Grayscale charts. The more recent selection appears in 3....For grayscale charts (selections 6 or 7) you'll be asked to select the chart type. You can also enter the reference file. Select the image file to read. Select the region (ROI), following the instructions. You may need to make a coarse region selection followed by a fine selection. Several charts allow automatic region selection. Select the Results Display. Because Color/tone Interactive is highly interactive you can change the Color space, reference file and other settings. You can calculate a Color Correction Matrix (CCM). Many saved settings are shared with Color/Tone Auto (formerly Multitest).

Photograph or scan the chart, taking care to illuminate the chart evenly (±5%) and avoid glare, which can be problematic in charts with semigloss (SG) or glossy surfaces such as the reflective IT8.7 and ColorChecker SG. Glare can be especially difficult to control with wide angle lenses. To minimize the effects of light falloff in lenses, the chart should typically not fill the image field (especially for wide angle lenses and/or high-resolution images).

Lighting recommendations can be found here. For testing white balance, you can photograph the chart in a scene under a variety of lighting conditions. The ColorChecker Passport Photo is especially suitable for this purpose. Some rectangular charts may be rotated by multiples of ±90° if they are geometrically symmetrical (these include the ColorCheckers (Classic 24-patch and SG) and the Kodak/Tiffen Q-13/Q-14, but not the IT8.7 (where top and bottom are different).

To start Color/Tone Interactive, run Imatest, then click the Color/Tone Interactive button. The Color/Tone Interactive window will appear with brief instructions, which may be more up-to-date than the one shown below.

Color/Tone Interactive opening window with brief instructions

A standard Windows dialog appears with the chart type indicated in the title.

Open an image file by either pressing Read image file if the correct Chart type is displayed or by selecting a chart from the Chart type dropdown menu immediately above Read image file . The Chart dropdown has a two-tiered menu, which allows you to select color, multi-row grayscale, or linear grayscale charts. Color charts are shown below.

To calculate temporal noise, select either two files (for the Imatest-recommended difference method) or 4-16 files (for the ISO 15739 method). Details of the calculation are can be found here.

Supported charts (not all are shown below)

Select a chart to analyze by clicking on one of the entries in the Chart type popup menu described above or by clicking on Read image file if the correct Chart type is displayed. The Read image file button and popup menu (shown on the right) are highlighted (yellow background) when Color/Tone Interactive starts. Color/Tone Interactive and Auto support all charts shown and described below:
	The standard 24-patch X-Rite ColorChecker® Classic. ColorChecker charts (Classic and SG) are available in the Imatest store and from a great many suppliers worldwide. Images of both the 24-patch ColorChecker and SG can be found in Imaging-Resource.com camera reviews (in the samples section). Danny Pascale/Babelcolor's page on the ColorChecker contains nearly everything you want to know about the chart.  Builds of Imatest 5.1 after May 2018 can read pre and post-2014 Colorchecker values from CGATS files posted on this page.
	The industry-standard IT8.7 chart. IT8.7 charts come in several formats (reflective and transmissive), available from Wolf Faust. A high-gamut version may be available from Hugo Rodriguez (website in Spanish). Reflective IT8.7/2 charts are relatively inexpensive. IT8.7 charts are usually printed on photographic paper or film (consisting of three dye layers). They must be used with reference files, which are available from manufacturer's websites. As of 2025, the IT8.7 is used infrequently, and we do not recommend it for new projects.

	The 140-patch X-Rite Colorchecker SG (Imatest Master & IS-only), which has a semigloss (SG) surface. It contains a 6x4 patch area in the upper-middle that is similar to the 24-patch Colorchecker, except that the colors are more saturated. Available from the Imatest Store. Imatest can read pre and post-2014 Colorchecker SG values from CGATS files posted on this page.
	Linear grayscale step charts (consisting of a single row of patches) such as the Kodak/Tiffen Q-13/Q-14 (inexpensive and widely available) or the Stouffer T4110 (Dmax = 4.0). Both reflection and transmission charts are supported. Charts with circular patterns (shown below) are preferred because they're less susceptible to errors from lens light falloff (vignetting). Other stepcharts are discussed in Using Stepchart.
	Reflective Multi-row grayscale charts (Imatest Master-only): These charts are less susceptible to measurement errors from light falloff than linear charts. Left:   ISO-15739 Right: ISO-14524
	Transmissive Multi-row grayscale charts for Dynamic Range measurements (Imatest Master-only) Right: Contrast Resolution Chart - Also for Contrast detection probability (CDP)
	TE269  For Dynamic Range measurements. You can choose between the original version and the newer TE269V2 or V3 (which have the same geometry as the Imatest 36-patch DR chart, but different numbering) in a dropdown menu in the Chart configuration area of the ROI Options window. Three reference files are available, derived from data on the manufacturer's website:  TE269A | TE269B | TE269C
	DSC Labs ChromaDuMonde 28/28R widely used in the cinema and broadcasting industries for calibrating cameras. Useful with the vectorscope display. Imatest Image Acquisition features auto-refresh for full vectorscope functionality.
	The Universal Test Target (crop shown on right) is primarily designed for testing scanners. Color/Tone Interactive can analyze the 9x3 color pattern to the left of center (with the 9 light regions at the bottom) as well as the 20-step grayscale step charts (which have step increments of L* = 5). When the stepchart is analyzed (using 6. Stepchart (linear)), Ref (Reference file or data source) should be set to L* = 95:-5:5,1 (20-step UTT).
	General mxn charts (4x12 shown on the left). Any chart with an m×n grid can be analyzed. You must specify the grid size by clicking Settings, then entering the number of rows (m) and columns (n) on the lower-right of the Settings window. We recommend doing this after opening Color/Tone Interactive, but before reading the image. You must also enter a CSV or CGATS file with reference patch settings (typically L*, a*, b* values, one set per line). If you have a spectrophotometer you can create a custom reference file (CGATS format) using techniques described in Measuring test chart patches.
	SpyderCHECKR (8x6)  A small chart that competes with the Colorchecker. Should be oriented as shown. If you want to measure only half the chart (say, left or right), you'll need to create a reference file with L*a*b* data available here.
	RezChecker and ColorGauge (nano and micro) charts from Image Science Associates, available in the Imatest Store. Professional grade miniaturized targets made in cooperation with Munsell Color Services from the same 18 pigments as the ColorChecker. Also has 12 unique spectrally neutral glossy or matte gray patches for measuring dynamic range, tones, and imaging noise. The RezChecker slanted-edges have exceptionally high quality. Suitable for close up and macro photography. Reference data for for the version with glossy grayscale patches (max density = 2.42) is built into Color/Tone. You can download reference file for the chart with matte grayscale patches (max density = 1.485) here.  The patches are mounted on aircraft-grade anodized aluminum and are set below the top surface to help protect from damage. Nano patch sizes are 1/8” x 1/8”; 11/16” x 13/16” x 0.060” thick overall. Micro patch sizes are 1/4” x 1/4”; 1 -3/8” x 1-5/8” x 0.060” thick overall.
ISA can provide NIST-traceable measurements for Rezchecker patches. These measurements are in a difficult-to-use XLS/CGATS file format. To use this data as an Imatest reference file, open the file in Google sheets (which can be done directly in Gmail) or in Excel. Select the 30 rows representing the patches and the 3 column representing LAB L, LAB A, and LAB B, and copy them into the clipboard. Past into a text editor and save the file (with txt or csv extension). This will work well as a reference file.
Other charts: SFRplus 20-patch color, SMPTE/Hale Color Bars (6 patches), Image Engineering TE226 (9x5). We occasionally add charts on customer request.

If the image is the same size and type as the previous image analyzed by Color/Tone and if Automatic region detection has not been selected (available for a limited number of charts), you'll be asked if you want to use the same ROI (region of interest).

If the image is not the same size and type, or if you answer No, a coarse cropping box appears. The initial crop doesn't have to be precise: you'll have a chance to refine it shortly. The crop box can be enlarged or maximized to make the selection easier.

• For either of the ColorCheckers (24-patch or SG), leave a margin around the sides slightly smaller than the spacing between patches.
• For grayscale step charts, select the entire chart (all patches), choosing boundaries that give even patch size. (The white patch on the Q-13 and Q-14 is larger than the rest.)
• For IT8.7 charts, select an area that includes the boundaries around the color chart and the entire grayscale (the red rectangle in the fine adjustment box below).

Special settings for linear grayscale charts

If you selected Linear grayscale (6. Grayscale Stepchart (linear*) and clicked No, select new ROI(s) in the ROI repeat window (if it appears)), the box shown on the right appears. Select the chart type (which specifies the density step) and the number of patches (between 6 and 41). Kodak/Tiffen Q-13/Q-14 charts have 20 patches; the Stouffer T4110 (a transmission chart with a density range of 4.0) has 41. For the Universal Test Chart (UTT) L* = 95:-5:5,1 (20-step UTT) and 20 patches should be selected.

*Linear charts have a single row of patches.

Stepchart type (reflective/transmissive, density step)

To correctly analyze the 36-patch High Dynamic Range (HDR) chart you must enter the individually-measured reference file.

Once you've made the rough crop, the fine adjustment box appears. The original crop is displayed as the red rectangle. The patch regions to be selected are the small cyan squares or rectangles. This dialog box can be enlarged or maximized to facilitate the adjustment. It offers numerous options.

• The entire ROI can be moved ( ^ > v < , upper-left).
• The top, bottom, left, or right sides can be moved ( T^ Tv R> R< B^ Bv L> L< , middle-left).
• Corners can be moved individually (any of the 8 buttons in each of the four corners, middle-left).
• Pixel values for the four corners can be entered (X(tl), Y(br), ..., where tl = top-left, br = bottom right, etc.). The origin is the upper-left. Be sure to press the Enter key after entering a value.
• You can choose between Fine and Coarse movement (1 or 5 pixels of movement per click).
• The display can be zoomed out or in.
• The display can be lightened to view the dark regions more clearly.
• For some charts (those with relatively large patches) a Fill factor (linear) slider in the gray area above the No, Try again button specifies the relative size of the squares. Its default value is 0.5. Smaller values can be used where lens distortion or pattern alignment makes alignment difficult.
• The distortion slider allows highly distorted images (barrel or pincushion) to be analyzed.

When you have completed the fine adjustment, click one of the buttons on the bottom of the window. If you click Yes, Continue, an additional dialog box may appear. For example, for the IT8.7 chart it will ask for the required reference file. Some of the entries in the input dialog boxes, like color space, can be changed later. If you click Yes, Continue in Express mode , it will go directly to the Color/Tone window, using saved (most recent) values. For example, it saves the IT8.7 reference file name.

To save ROIs for use in future runs or to retrieve ROIs saved in past runs, follow the instructions in How to save and retrieve region selections. The ROIs are for the individual chart (Colorchecker, Contrast Resolution, etc.), not for Color/Tone as a whole.

The Color/Tone Interactive window

After the image file has been entered, the most recent Chart view is displayed. The 2D a*b* view (ideal and input values on the CIELAB a*b*) is shown below.

The main display image is on the upper left. Color differences are summarized below this image, except when the Probe is turned on (available for the pseudocolor and split color displays). The various ?E* and ?C* values are described in in Wikipedia. A thumbnail image of the chart is shown on the upper right. Available options are described below. The remainder of the right side is the control area.

The Zoom/Rotate 3D/Data Cursor dropdown menu, just below the upper-right thumbnail, determines the action when you click on the image.

Zoom	Click on the image or select an area to zoom into. Double-click to zoom out.
Rotate 3D	Rotate 3D images by clicking and dragging the mouse. Zoom is activated for all other (2D) images.
Data Cursor	Display a data cursor (shown on the right) for several displays including 4. 2D a*b*, 5. xy Chromaticity, and 6. u'v' Chromaticity. When you click on Reference or Camera symbols, you get  a Data cursor with patch information: RGB and L*a*b* values (different for the reference and camera) and several color difference metrics.

The dropdown menu to the right of the Zoom/Rotate 3D/Data Cursor menu controls the display of the thumbnail image on the upper-right. The first two selections use the actual image. The rest use synthesized (reference and camera) patches.

Input image- whole	Shows entire input image
Input image- crop	Shows the cropped input image (all patches)
Ideal/Input split > sRGB	shows a split view of the ideal/camera patch values mapped to sRGB, which is similar to typical monitor color spaces. This is the default (recommended) setting (shown on the right for the X-Rite ColorChecker).
Ideal/Input split patches	shows a split view of the ideal/camera patch values with no gamut mapping. Colors will not be accurate for large gamut color spaces
Input > sRGB monitor	displays the input image mapped from its native color space to sRGB, which is similar to typical monitor color spaces
Input patches	displays the input image with no gamut mapping. Colors will not be accurate for large gamut color spaces
Ideal > sRGB monitor	displays the ideal image mapped from its native color space to sRGB, which is similar to typical monitor color spaces
Ideal patches	displays the ideal image with no gamut mapping. Colors will not be accurate for large gamut color spaces

Image area

The pale blue box on the right is the image area. It includes the Read image file button (and Reload button for Imatest Image Acquisition-only), the Chart type dropdown menu (described above), entries for image properties, and color correction matrix functions .

Reload (Imatest Image Acquisition-only) reacquires the image from a device or video stream (depending on how the image was originally acquired) or reloads it from a file.

Color space allows the input file color space to be selected. This color space is also used as the target for calculating the Color Correction Matrix (CCM). The color space is automatically read into Color/Tone from the EXIF data when ExifTool has been selected in Options II; otherwise it must be entered manually. Several color spaces are available. The first six are primarily for still images. Most of the rest are for video/cinema. See the Wikipedia RGB Color Space page and brucelindbloom.com for overviews.

Danny Pascale's A Review of RGB Color Spaces is recommended for readers interested in an in-depth explanation of color spaces.

Ref lets you select source for the reference (ideal) chart values, as described above. The dropdown menu contents depends on the chart type. For the 24-patch ColorChecker and the ColorChecker SG you can select either standard chart reference values or you can read in values from data files (Imatest Master and Image Sensor) in CSV or CGATS formats. Values for the two ColorCheckers have been supplied courtesy of X-Rite.

Correction matrix calculates the Color Correction Matrix (CCM). Prior to calculating the CCM you should make sure settings (linearization, etc.) are correct by clicking on Settings or clicking Settings (dropdown menu), Color matrix and other settings...  After Correction matrix has been pressed it changes to Matrix calculated, highlighted with a yellow background. The correction matrix cannot be recalculated until a property of the image (new image, color space, reference file, or color matrix setting) changes. The Display input (or Corrected) dropdown menu, immediately to its left, is enabled. More details on using the Color Correction Matrix can be found here.

Display selection menu and area

1. Pseudocolor color difference. Shows the difference between the ideal and input color patches using any of several metrics. The pseudocolor scale is shown adjacent to the image (below, right). Probe is available for this display. Not the most useful display
2. 3D color difference (with split colors).
3. Split colors: ideal/input. Shows the patches split so that the ideal and input values are displayed in the upper left and the lower right or each patch region, respectively. Probe is available for this display.
4. 2D a*b*.
   
5. xy chromaticity.
6. u'v' chromaticity.
7. Black & White density.
8. 3D L*a*b*. Shown on the right. L*a*b* coordinates can be difficult to visualize when viewed from a single angle. It needs to be rotated to be useful.
9. EXIF data and Color matrix. Shows EXIF data if available and the color correction matrix if it has been calculated.
10. Vectorscope preview. 
11. Noise analysis (not for all charts). A huge variety of noise, Signal-to-Noise Ratio (SNR) and Dynamic Range results are available, including ISO 15729 and CPIQ (Camera Phone Image Quality) results. See Color/Tone/eSFR ISO noise for more details. Not available for charts with tiny patches, like the IT8.7 and ColorChecker SG.
12. Display image.  Many options are available including display single channel, boosted colors, and lightened image.
13. Read - color-correct - Save image.  Can be used after CCM has been calculated to apply the Color Correction Matrix to any image. The corrected image can be saved.
14. 2D CbCr (from YCbCr). 
15. HS (Hue-Saturation) from HSV. 
16. HS (Hue-Sat) from HSL. 

The Display area, immediately below the Display selection box, contains display options. The contents, which depend on the display selection, are described below in the sections for the individual displays.

Save screen (shown on the right) saves a snapshot of the current display (the entire Color/Tonescreen) as a PNG file (a widely-used losslessly compressed format). It also allows you to immediately view the snapshot so it can be used a reference for comparing with other results.

File name and Directory at the top of the window set the location of the file to save.

When you check the Open window in an image viewer... box, the current screen will be opened either the system default viewer (if the box under Image viewer is blank) or a viewer/editor of your choice (if the box contains the path name to the viewer/editor). I recommend using Irfanview, which is fast, compact, free, and supports an amazing number of image file formats. Its normal location in English language installations is C:\Program Files\IrfanView\i_view32.exe.

Save data Saves the key data in CSV and XML formats. This includes the input R, G, and B values, the input and reference L*, a*, b* values, and several of the color difference metrics.

Help opens this web page in an HTML browser window.

Exit terminates Imatest Color/Tone, but the Imatest main window is still available.

More settings

Clicking the Settings button that appears in the Display area (for many displays) or clicking Settings (dropdown menu on top), Color matrix and other settings... or ISO speed, noise, mxn chart... opens the window shown below.

Dropdown menus File Settings Color ellipses INI File Settings Help

The Dropdown menus at the top of the Color/Tone window are used for a large variety of utilities and settings.

Displays and options

1. Pseudocolor Color difference Shows the difference between the ideal and input color patches using any of several metrics using a pseudocolor color map. If a color correction matrix has been calculated, the difference between the ideal and corrected patches are shown at the bottom. The pseudocolor scale is shown adjacent to the image. Probe (Checkbox; Pseudocolor and Split views) turns on the probe, illustrated below. When the probe is on, you can probe any patch by clicking on it. The probe data (for the individual patch), shown below the split display, includes a small image of the ideal and input patch colors, ideal and input RGB and L*a*b* values, and several ?E* and ?C* color difference metrics. (Corrected colors are used if a color correction matrix has been calculated and Display corrected has been selected.) The probe is turned off by clicking outside either of the images. ?E*ab, the geometric distance in L*a*b* space, is the most familiar, but ?E*94, which is lower for chroma differences in highly chromatic colors (with large a*2 + b*2), is a better measure of visual color difference. ?E*00 is the most accurate metric (based on an exceedingly complex designed-by-committee equation). More detail on color difference equations can be found here and in Wikipedia.	Pseudocolor display for IT8.7
Probe illustration Split display for IT8.7 illustrating Probe (available for pseudocolor and split color displays) Color difference type (Popup menu to the right of the Probe checkbox; also in 3D Color difference) Contains a list of color metrics (mostly difference metrics) including ?E*ab, ?C*ab, ?E*94, ?C*94, ?E00, ?C00, ?L*, ?Chroma, ?|Hue distance| , ?(Hue angle) , Chroma (input) and Chroma (output). Numbers (checkbox) displays numbers in the middle of patches if checked. Color map (Popup menu) allows you to select the color map. The WYRMBK color map shown goes from White - Yellow - Red - Magenta - Blue - Black.
2. 3D Color difference (with split colors) Uses the height of the patches to display the difference between the ideal and input colors. Any of several metrics (?E*ab, ?C*ab, ?E*94, ?C*94, ?E*CMC, ?C*CMC, ?E*00, ?C*00, ?L*, ?Chroma, ?|Hue distance|, ?Hue angle, Chroma (input), Chroma (output)) can be chosen. The faces show split colors: reference (upper-left)/input (lower-right). This allows you to compare visual color differences with standard color difference metrics. Can be zoomed and rotated. You can use this display to correlate ?E and ?C metrics with visual color differences. None of the metrics are perfect! The visual difference between the reference and input is often lower than the indicated differences because the color space and monitor gamuts (often sRGB) may be lower than the original chart gamut, especially for cyan and blue. Rotate (Toggle button; short for Auto rotate) starts rotating the image. Rotation is quite slow; it may be less useful than the 3D L*a*b* plot (below). The image continues to rotate until the next time you press the Rotate button. It's best to turn off rotation before switching to other views. Light (Checkbox) Illuminates the figure to make the sides darker. Checked (On) recommended. Color difference type (Popup menu) Described above under Pseudocolor display. Background lightness (Slider) sets the background gray level. Invert (Checkbox) inverts the up-down orientation of the 3D plot.	3D Color difference display for Colorchecker
3. Split colors Displays a synthesized chart image with each patch split so the ideal value is in the upper left and the input (measured) value is in the lower right. If a color correction matrix has been calculated, corrected colors are shown at the bottom. Probe (Checkbox) is the only option. Described above under Pseudocolor display. Numbers (checkbox) displays numbers in the middle of patches if checked.	Split Color display for IT8.7
4. 2D a*b* Displays patch values on the CIELAB a*b* plane. Ideal values are displayed as squares; Input values are displayed as circles. Color difference ellipses (representing ?Cab, ?C94, or ?C2000 can be displayed. A Color Difference Visualizer (separate from Color/Tone Interactive) has been added so you can interactively examine the appearance of color differences. Expand (Checkbox; 2D a*b*, xy chromaticity, u'v' chromaticity, and 3D L*a*b*) Zoom in so the data fills the image. Region (Popup menu in the lower right of the Display area; also in xy chromaticity, u'v' chromaticity, and 3D L*a*b*) selects the region of the chart to display. For the IT8.7 and ColorChecker SG charts only. Avoids clutter from the large number of patches in these charts. For the IT8.7: Selections are Columns 1-4 (dark), 5-8 (middle), 9-12 (light), 13-19 (CMYKRGB primaries), and 20-22 (miscellaneous; unique to each chart manufacturer). Columns 13-19 are the most interesting.  For the ColorChecker SG: Regions are less geometrically regular. Selections are 24-patch replica (middle), Pastels & skin tones, mid tones, and dark tones.	2D a*b* display for IT8.7
Histograms (available with plots 1-4: Imatest 2021.2+) If histograms are selected in the dropdown menu in the plot settings area (below), a pair of color error histograms, as indicated (ΔEab & ΔCab or ΔE00 & ΔC00), appears between the main figure and the color error summary. The dropdown menu is in a different location for plots 3 and 4. The histograms are useful for comparing color errors without and with a color matrix (CCM) applied.	ΔE00 & ΔC00 histograms in plot 2
5. xy and 6. u'v' Chromaticity Displays the xy and u'v' Chromaticity diagrams, which separate the visible and invisible color values into colored and gray regions. Ideal values are displayed as squares; Input values are displayed as circles. Color difference ellipses (representing ?Cab, ?C94, or ?C2000 can be displayed. The u'v' Chromaticity diagram, which is more perceptually uniform than the more familiar xy diagram is illustrated on the right. Wavelth (Checkbox) Turns the wavelength display (400-700 microns) on the periphery of the locus of visible colors on or off. View (Popup menu to the right of Wavelth) selects between normal color (about as good a representation as is possible on a monitor) and lightened color (slightly easier to see the patch values). Expand (Checkbox) Zoom in so the data fills the image. Region (Popup menu in the lower right of the Display area) Described above under 2D a*b* display.	u'v' display for ColorChecker SG
7. Black & White density   Shows the grayscale response curve. Available for all currently-supported color charts because all of them contain grayscale regions. Display type (Popup menu) allows you to select one of several B&W displays. Log pixels vs. input density. (shown on right) Gamma is the average slope for the lighter levels. The luminance (Y) channel is emphasized, but R, G, and B channels are also shown. Output vs. input density. The slope is ideally 1. Density is proportional to -Log10(Luminance). Output vs. input luminance. Shown on a linear scale. Output vs. input L* a* b* c*. Uses CIELAB values instead of density or (linear) luminance. Includes color values: a* (green-red), b* (blue -yellow), and c* (chrominance: (a*2 + b*2 )1/2 ). When the B&W density plot is displayed, you can enter the incident lux level into a box in the Display area on the lower right of the Color/Tone window. If the value is a positive number (not blank or zero) ISO Sensitivity will be calculated and displayed on the plot.	Log pixels vs. input density for Q-13
8. 3D L*a*b* Displays patch values in 3D CIELAB L*a*b* space with a wireframe representing the boundaries of the selected color space. Ideal values are displayed as squares; Input values are displayed as circles. Can be zoomed and rotated; you need to rotate it to be able to visualize patch locations. Wireframe properties (Popup menu) Turns wireframe on, off, or on with minimal (coarse) grid. A-rotate (Toggle button; short for Auto rotate) starts rotating the image. This provides a better visual indication of the color locations. The image continues to rotate until the next time you press the A-rotate button. It's best to turn off rotation before switching to other views. Transparency (Slider; default = 1) sets the wireframe transparency.Reducing transparency below 1 differentiates patches outside and inside the wireframe gamut boundary. Results are not reliable: patches near the boundary don't always appear as they should. Background (Slider) sets the background gray level. Region (Popup menu in the lower right of the Display area) Described above under 2D a*b* display. Expand (Checkbox) Zoom in so the data fills the image.	3D L*a*b* display for ColorChecker
10. Vectorscope (not in Studio) Duplicates the display of hardware vectorscopes, used for adjusting and calibrating broadcast and cinema cameras. It is designed to work optimally with the DSC Labs ChromaDuMonde 28 chart. (Other DSC charts will be added as customer demand warrants.) There are several display options, including background color, reference and input display color. Light input colors (circles) and dark reference colors (squares) are shown on a dark background. HDTV, SDTV (similar to YCbCr below), and NTSC/PAL vectorscope patterns can be displayed. The recommended color space for these signals is sRGB. For now the vectorscope omits the standard target rectangles because the RGBCMY primaries in the CDM chart are different from the standard color bars. This image is a preview of a full-featured vectorscope function that will be included in an upcoming broadcast/cinema version of Imatest that continuously refreshes frames from a video stream using the Reload button instead of reading individual images from files.	Vectorscope preview
11. Noise analysis (for charts with large enough patches) Color/Tone supports a variety of noise and SNR (Signal-to-Noise Ratio) analyses, including plain pixel noise, chroma noise, CIELAB (L*a*b*) noise, Dynamic Range analysis, Photon Transfer Curves (noise or SNR as a function of Digital Number (DN) for Simatest, and ISO 15739 visual noise. These measurements are for the grayscale patches. The measurements include a set of measurements for all patches (color as well as grayscale) that is meaningful for undemosaiced raw images (i.e., no tonal response curve or color matrix applied). In such systems, noise is proportional to a constant plus the square root of the pixel level. This measurement allows you to determine the sensor dynamic range (using a fairly reliable extrapolation). See Color/Tone noise for more detail.	SNR measurement
12. Display image The image can be displayed to verify the region settings and to explore the patche images (under a variety of conditions-- normal view, intensified color, lightened, etc.). Options: Image display (dropdown menu; title not displayed due to space limitations) allows you to select Original image, individual channel (R, G, B, Y, mean), chroma-boosted image, lightened image (several versions), etc. Useful for finding issues in the image as a whole or in individual patches. Display patch ROIs (checkbox) Turns red ROI rectangles on or off. Crop (checkbox) If Crop is checked, a dropdown menu is opened, just to the right of the Crop checkbox, that allows you to select Whole crop or the individual patch.

13. Read – color correct – Save image

Once a color correction matrix has been calculated, the matrix can be used to correct arbitrary images. To do so, select 11. Read - color correct - save image in the Display box on the right of the Color/Tone window. The initial display on the left side contains the message, Press "Read image to correct", then press "Save corrected image" if it looks OK., the color correction matrix and statistics, and two buttons: Read image to correct and Save corrected image.

In the case shown on the right, a (digital) CC20C (cyan) filter was applied to both the Colorchecker and Gallery image. The correction matrix was calculated for the filtered Colorchecker, then the filtered Gallery image (shown uncorrected on the top) was read in. The corrected image is shown on the bottom.

Color correction on an arbitrary scene

14. YCbCr plot

Displays results on the CbCr plane of YCbCr color space. Similar to the Vectorscope plot with SDTV selected.

Expand (Checkbox; available in several 2D plots) Zoom in so the data fills the image.

15. HS (from HSV) and 16. HS (from HSL) plots

Displays H (Hue) angle and S (Saturation) radius for HSV and HSL color representations, respectively. These representations are relative to the color space gamut boundary, which is located at radius = S = 1, i.e., they are not device-independent.

Expand (Checkbox; available in several 2D plots) Zoom in so the data fills the image.

YCbCr plot

H (Hue) and S (Saturation) from HSV

H (Hue) and S (Saturation) from HSL

 

17. 3D Image Surface plot

The surface height is the luminance (Y-channel) of the image.

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ColorChecker^® is a trademark of X-Rite, Incorporated, which is not affiliated with Imatest. ColorChecker L*a*b* values are supplied courtesy of X-Rite.

分析顏色和灰階測試圖表
在一個固定的、能夠進行批次處理的模組中

Color/Tone Auto（以前稱為 Multitest）包含了Color/Tone Interactive （以前稱為 Multicharts） 、 Colorcheck和Stepchart中的所有計算。

介紹

Imatest™ Color/Tone Auto是一款色彩/色調自動分析軟體，它使用固定介面批次處理影像，可分析各種測試圖表的影像，評估其色彩準確度、色調響應、雜訊、信噪比 (SNR) 和ISO 感光度。該軟體能夠測量各種光照條件和場景下的白平衡和色彩響應，並可顯示單色圖表（或彩色圖表中的單色部分）的色調響應。此外，它還能計算色彩校正矩陣。

Color/Tone Auto可以分析Color/Tone Interactive支援的所有圖表，並產生大部分結果圖。它還整合了Colorcheck和Stepchart模組的所有重要功能：操作方式類似，但能夠分析更多圖表並顯示更多結果。

一套完整的圖表及其使用指南都在其中。
顏色/色調測試圖表參考及指南

Color/Tone Auto 支援的常用測試圖表

24個補丁 顏色檢查器		IT8.7		對比度分辨率		Colorchecker SG		DSC Labs Chroma- 杜蒙德 24+4R
		Q-13/Q-14 以及其他 灰階 步驟圖		普遍的 測試目標		顏色規 （微米、奈米等）		RezChecker
SpyderCHECKR		ISO-15739		墨西哥將軍 圖表（L*a*b* 參考文件 必需的）		TE269，TE269V2 （2 個版本）		ISO-14524
另附：SFRplus 20色塊色卡、SMPTE/Hale 色條（6色塊）、TE226（9x5）色卡

支援的圖表的更完整列表可在“顏色/色調 - 支援的圖表”中找到。

入門

拍攝或掃描色卡時，請注意均勻照明（誤差±5%），並避免眩光。對於半光澤（SG）和光面色卡（例如反光的IT8.7和ColorChecker SG），眩光問題特別突出。使用廣角鏡頭時，眩光控制尤其困難。為盡量減少鏡頭光線衰減的影響，色卡通常不應充滿整個畫面。

《建造低成本測試實驗室》一文介紹了一種低成本的照明方案。為了測試白平衡，您可以在各種光線條件下拍攝場景中的色卡。小型版的 ColorChecker 色卡（例如Passport 、 SpyderCheckr或 ColorGauge 色卡）尤其適合此用途。某些矩形色卡如果幾何對稱，可以旋轉 ±90° 的倍數（例如兩款 ColorChecker 色卡和 Kodak/Tiffen Q-13/Q-14，但不包括IT8.7，因為其上下兩面不同）。

在執行“顏色/色調自動”功能之前，您應該選擇要分析的圖表類型。點選Imatest主視窗（如右圖）中「顏色/色調自動」按鈕右側的「設定」按鈕，或點選「固定模組」 > “顏色/色調自動設定” 。這些操作將開啟「顏色/色調自動」設定窗口，如下圖所示。 圖表類型下拉式選單（位於「顏色/色調自動設定」視窗中，如右側所示）包含所有可用的圖表設定。 選擇完成後，該設定將被儲存並顯示在「顏色/色調自動」按鈕中，如右上圖所示。 可以在此時或讀取圖像檔案並選擇感興趣區域 (ROI) 後更改其他設定（除非您選擇了快速模式）——但由於圖表類型總是會影響下一次運行，因此在運行新的圖表類型之前應該進行選擇。 圖表選擇下拉式選單 運行“顏色/色調自動”之前應選擇圖表類型。
		圖表類型（用於下次顏色/色調自動運行）

自動區域偵測

這也是選擇自動或手動區域檢測的好時機，該功能位於「顏色/色調自動」設定視窗的底部，並且對允許自動選項的圖表啟用（最初是Colorcheck和36 色塊動態範圍圖表，未來會有更多）。

執行顏色/色調自動功能—要啟動顏色/色調自動功能，請執行Imatest ，然後按一下「顏色/色調自動」按鈕。此時將開啟一個窗口，供您選擇文件（或一批文件）。

若要計算時間噪聲，請選擇兩個檔案（用於 Imatest 建議的差分法）或 4-16 個檔案（用於 ISO 15739 方法）。計算詳情請參閱此處。

如果您選擇了手動 ROI 偵測，在選擇檔案後，Imatest 會檢查映像大小是否與最近執行的映像大小相同（它會儲存多種尺寸的影像）。如果大小相同，系統會詢問您是否要重複選擇相同的興趣區域 (ROI)：

如果影像大小與先前的影像不同，或者您點擊「否，選擇新的 ROI」 ，則會彈出一個窗口，要求您選擇區域。您可以透過在要分析的圖表上從一個角落到另一個角落繪製一個矩形來完成此操作。不必擔心區域是否完全精確——您可以對其進行微調。

初步（粗略）區域選擇。在圖表上從一個角落到另一個角落繪製一個矩形。
圖片來自Imaging-resource.com （來自單一相機評測範例頁面的多目標）。

在粗略選擇後開啟的精細選擇視窗中，對選擇區域進行更精確的調整。不同圖表的內部方框可能會有所不同。 （注意：如果您選擇了「自動 ROI 偵測」選項，並使用支援自動偵測的圖表進行確認，則會顯示此視窗。）

• 整個 ROI 可以移動（^ > v <，左上）。
• 頂部、底部、左側或右側可以移動（T^ Tv R> R< B^ Bv L> L<，中間向左）。
• 可以單獨移動四個角落（左中角的 8 個按鈕中的任何一個）。
• 您可以輸入四個角點的像素值（ X(tl) 、 Y(br) 、…，其中tl代表左上角， br代表右下角，以此類推）。原點位於左上角。輸入數值後請務必按回車鍵。
• 您可以選擇精細、粗糙或超粗糙 (XC-25) 移動（每次點擊移動 1、5 或 25 像素）。
• 顯示內容可以縮小或放大。
• 可以調亮顯示屏，以便更清楚地查看暗部區域。
• 對於某些圖表（尤其是色塊較大的圖表），「失真」滑桿左側的「填充因子（線性）」滑桿用於指定方塊的相對大小。其預設值為 0.5。當鏡頭畸變或圖案對齊導致對齊困難時，可以使用較小的值。
• 「失真」滑桿可分析高度失真的影像（桶形失真或枕形失真）。

完成微調後，點擊視窗底部的按鈕之一。如果按一下「是，繼續」 ，則會開啟如下所示的「色彩/色調自動」設定視窗。如果按一下「是，繼續」進入快速模式， 「色彩/色調自動」功能將運行，顯示選定的結果圖，並儲存選定的結果檔案。

圖表類型	選擇圖表類型。應用於下次運行。如果選擇圖表類型 3（最後灰階圖）或 7（多行灰階階梯圖（非線性）），則應在下面的「特殊（多行）灰階圖表類型」下拉式選單中選擇特定的圖表類型。
更多設定：顏色矩陣、雜訊、鏡像/旋轉…	打開顏色/色調設定窗口，如下圖所示。您可以選擇顏色矩陣設定（詳見顏色校正矩陣網頁）、雜訊設定、ISO感光度計算、MXN圖表設定等，如下所述。
運行顏色矩陣	如果選中，則計算並套用顏色校正矩陣（CCM）。
參考	參考文件。可以是標準格式，也可以是讀取格式（通常從 CSV 或 CGATS L*a*b* 或密度檔案讀取）。具體格式會因圖表類型而略有不同。
色彩空間	色彩空間
噪音計算。	噪音計算。選擇 1. 無（非視覺）噪音計算（最快），2. 基本噪音計算（較慢），或 3. 高級噪音計算（較慢）。
噪音和視覺噪音設置	開啟「雜訊與視覺雜訊」窗口，說明請參閱「色彩/色調互動式/自動/eSFR ISO 雜訊」 。您可以在此選擇視覺雜訊和其他設定。
非均勻性校正	允許您使用在相同條件下拍攝的單獨平場影像來校正非均勻照明。打開“非均勻性校正”窗口，該窗口在灰階和彩色圖表模組的“非均勻性校正”部分中進行了描述。
特殊（多行）灰階圖表類型	僅當選擇圖表類型 3（最後灰階圖）或 7（多行灰階階梯圖（非線性））時可見。用於選擇合適的灰階圖表類型。
特殊灰階圖表設置	開啟一個窗口，讓您選擇線性灰階階梯圖的密度增量。
在右側顯示縮圖和 EXIF 資訊。	在圖表右側顯示整個影像和裁切區域的縮圖以及 EXIF 結果。示例如下圖所示。
繪圖設定（右側）	選擇輸出數據。具體說明如下。

色彩校正矩陣	CCM 計算的設定說明請參閱「顏色校正矩陣」頁面。
事件 Lux	必須手動輸入ISO感光度（曝光指數）計算所需的參數。光圈和曝光時間（秒）通常從EXIF資料中獲取，但如果EXIF資料缺失，則可以手動輸入。
噪音	設定說明請參閱「顏色/色調/eSFR ISO 雜訊」頁面。
列、行 通用 MXN 圖表	選擇通用m x n （矩形）圖表的行數和列數。選擇此圖表需要參考文件。
飽和度	輸入影像的最大像素等級（對應於飽和度等級），用於對影像資料進行歸一化以進行某些計算。 標準檔案：255（或 65535...） ：飽和度等級會根據影像資料的資料類型和容器大小自動設定。這是預設值。影像檔案假定具有標準位元深度（例如，8 位元、16 位元或 32 位元資料）和標準飽和度等級。例如，對於標準的 8 位元影像數據，飽和度等級將設定為 255。對於 16 位元影像，飽和度等級將設定為 65535，而對於 32 位元影像，飽和度等級將設定為 4294967295。 ITU-R 建議 601 (BT. 601: 235) ：飽和度等級設定為 235。 最大偵測到的色塊等級：飽和度等級設定為影像中色塊區域偵測到的最大值。如果影像資料的位元深度不標準（例如，12 位元資料儲存在 16 位元容器中），或者存在自訂飽和度級別，只要影像曝光足以使最亮的色塊達到飽和狀態，此功能就非常有用。 手動輸入飽和度：飽和度等級設定為使用者輸入的值。如果影像資料的位元深度不標準，或存在自訂飽和度級別，則此功能非常有用。例如，對於儲存在 16 位元容器中的 12 位元資料的影像，飽和度等級應輸入 4095（2^12 - 1 = 4095）。
像素偏移	輸入要從資料中減去的像素偏移量。像素偏移很常見：它們會導緻密度曲線過早趨於平緩。
非均勻性校正	允許您使用在相同條件下拍攝的單獨平場影像來校正非均勻照明。打開“非均勻性校正”窗口，該窗口在灰階和彩色圖表模組的“非均勻性校正”部分中進行了描述。
影像方向	（適用於下次讀取）選擇標準影像方向、鏡像（水平翻轉）、鏡像（垂直翻轉）、旋轉 180 度。

結果數據

1. 3D 色差（含分割）

在此圖中，區域的高度代表選定的顏色差異，在本例中為 ΔE* _ab （即 Delta-E）。色塊平台的頂部以雙色顯示，左上角為參考色，右下角為實際輸入顏色。此圖可用於比較測量顏色與感知顏色差異。 （它們可能與理論聲稱的匹配度不完全一致。）

此圖表右側會顯示縮圖和 EXIF 資料（在「色彩/色調自動設定」視窗中勾選複選框即可設定）。其他圖表將不顯示這些結果，即未勾選該複選框（這樣可以節省空間）。

2. 分割顏色（參考/輸入）圖 分割顏色圖顯示左上角的參考（理想）顏色和右下角的輸入顏色。 如果已計算顏色校正矩陣（如果已選取核取方塊），則此圖以及 3D 顏色差異圖（上圖）將在左上角顯示參考顏色，在右上角顯示輸入顏色，在底部顯示校正後的顏色。 3D色彩差異細節， 計算顏色校正矩陣
3. 二維 a*b* 圖 顯示 L*a*b* 色彩空間的 a*b* 平面。色度差異（非常）近似於參考值和相機值之間的距離。 （此差異為 ΔC <sub>ab</sub> 。較複雜的 ΔC<sub> 94</sub>和 ΔC<sub> 00 </sub> (CIEDE 2000) 方程式（此處有描述）較為精確。） 如果已計算出顏色校正矩陣，則會顯示校正後的值。
4. XY色度 這張圖雖然很常見，但與上面的a*b*圖相比，在視覺上不夠均勻。綠色在這張圖中所佔的面積過大。 如果已計算出顏色校正矩陣，則會顯示校正後的值。
5. 黑白密度和白平衡 上圖顯示 Log(像素等級/255)（最大值為 1）與輸入密度（-log 10 （曝光））的關係，即使用密度單位。 下圖展示了幾種不同色塊密度下的ΔC值。參見顏色檢查附錄。 如果已計算出顏色校正矩陣，則會顯示校正後的值。
6. EXIF 資料和色彩矩陣 此圖顯示了選定的 EXIF 資料和顏色矩陣校正結果，包括 色彩矩陣 用於計算矩陣的設定說明（用於最佳化的顏色差異、加權、線性化等） 輸入影像與參考影像之間以及校正影像與參考影像之間的平均色彩差異和最大色彩差異。
7. 附加二維彩色圖 此處顯示向量示波器介面。您可以在此處選擇幾個圖表之一： u'v' 色度 向量示波器 2D CbCr（源自 YCbCr） 來自 HSV 的 HS（色調-飽和度） 來自 HSL 的 HS（色相-衛星） 這些顯示方式在「使用顏色/色調 - 顯示和選項」中有詳細說明。
雜訊/訊號雜訊比分析（並非所有圖表都適用） 雜訊/訊號雜訊比分析僅適用於影像區塊足夠大、能夠提供良好雜訊統計資料的圖表。雜訊分析包括標準像素雜訊、色度雜訊、場景參考雜訊、感測器（原始）雜訊和 ISO-15739 視覺雜訊。訊號雜訊比 (SNR) 可以以比值或分貝 (dB) 的形式顯示。 本頁所示的 ColorChecker SG 色塊太小，但幸運的是，Imaging-Resource 影像在 SG 的左側有一個標準的 24 色塊 ColorChecker，我們對其進行了分析，從而得到了右側所示的結果。 噪音分析在「顏色/色調」和「eSFR ISO 雜訊」部分有詳細描述。 ISO 15739 視覺雜訊已加入Imatest 4.0 。 可供選擇的選項如下。 雜訊與輸入密度（RGB） 像素雜訊或最大像素等級的百分比 訊號/雜訊 (S/N) 與輸入密度 (RGBY) 亮度（Y 通道）用於 S。 SNR (dB) 與輸入密度 (RGBY) SNR (dB) = 20 log 10 (S/N)。 如右上方所示。 色度雜訊與輸入密度 色度訊號雜訊比與輸入密度的關係 色度訊號雜訊比（dB）與輸入密度的關係 CIELAB (L*a*b*)噪音 CIELAB (L*a*b*) 訊號雜訊比 CIELAB (L*a*b*) 訊號雜訊比 (dB) 雜訊與像素（所有影像區塊）這些測量結果對於表徵原始（未經處理或僅經過少量處理的）影像中的感測器性能至關重要。 信噪比與像素（所有色塊） 訊號雜訊比（dB）與像素（所有影像區塊）的關係 光圈（場景參考）雜訊和動態範圍 光圈（場景參考）訊號雜訊比和動態範圍。動態範圍等級以粗水平線（黃色、橘色等）顯示。 如右圖所示。 光圈（場景參考）訊號雜訊比（dB）和動態範圍 ISO 15739 視覺噪音 (L*u*v*) ISO 15739 視覺訊號雜訊比 (L*u*v*) 以分數表示 ISO 15739 視覺訊號雜訊比 dB (L*u*v*) 分貝 (dB) = 20*log 10 (分數)