色彩/色调

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.

分析颜色和灰度测试图表
在一个固定的、能够进行批量处理的模块中

Color/Tone Auto（以前称为 Multitest）包含了Color/Tone Interactive （以前称为 Multicharts） 、 Colorcheck和Stepchart中的所有计算。

介绍

Imatest™ Color/Tone Auto是一款色彩/色调自动分析软件，它使用固定界面批量处理图像，可分析各种测试图表的图像，评估其色彩准确度、色调响应、噪声、信噪比 (SNR) 和ISO 感光度。该软件能够测量各种光照条件和场景下的白平衡和色彩响应，并可显示单色图表（或彩色图表中的单色部分）的色调响应。此外，它还能计算色彩校正矩阵。

Color/Tone Auto可以分析Color/Tone Interactive支持的所有图表，并生成大部分结果图。它还集成了Colorcheck和Stepchart模块的所有重要功能：操作方式类似，但能够分析更多图表并显示更多结果。

一套完整的图表及其使用指南都在其中。
颜色/色调测试图表参考及指南

Color/Tone Auto 支持的常用测试图表

24个补丁 颜色检查器		IT8.7		对比度分辨率		Colorchecker SG		DSC Labs Chroma- 杜蒙德 24+4R
		Q-13/Q-14 以及其他 灰度 步骤图		普遍的 测试目标		颜色规 （微米、纳米等）		RezChecker
SpyderCHECKR		ISO-15739		墨西哥将军 图表（L*a*b* 参考文件 必需的）		TE269，TE269V2 （2 个版本）		ISO-14524
另附：SFRplus 20色块色卡、SMPTE/Hale 色条（6色块）、TE226（9x5）色卡

支持的图表的更完整列表可在“颜色/色调 - 支持的图表”中找到。

入门

拍摄或扫描色卡时，注意均匀照明（误差±5%），并避免眩光。对于半光泽（SG）和光面色卡（例如反光的IT8.7和ColorChecker SG），眩光问题尤为突出。使用广角镜头时，眩光控制尤其困难。为尽量减少镜头光线衰减的影响，色卡通常不应充满整个画面。

《搭建低成本测试实验室》一文介绍了一种低成本的照明方案。为了测试白平衡，您可以在各种光照条件下拍摄场景中的色卡。小型版本的 ColorChecker 色卡（例如Passport 、 SpyderCheckr或 ColorGauge 色卡）尤其适合此用途。某些矩形色卡如果几何对称，可以旋转 ±90° 的倍数（例如两款 ColorChecker 色卡和 Kodak/Tiffen Q-13/Q-14，但不包括IT8.7，因为其上下两面不同）。

在运行“颜色/色调自动”功能之前，您应该选择要分析的图表类型。点击Imatest主窗口（如右图所示）中“颜色/色调自动”按钮右侧的“设置”按钮，或者点击“固定模块” > “颜色/色调自动设置” 。这些操作将打开“颜色/色调自动”设置窗口，如下图所示。 图表类型下拉菜单（位于“颜色/色调自动设置”窗口中，如右侧所示）包含所有可用的图表设置。 选择完成后，该设置将被保存并显示在“颜色/色调自动”按钮中，如右上图所示。 可以在此时或读取图像文件并选择感兴趣区域 (ROI) 后更改其他设置（除非您选择了快速模式）——但由于图表类型总是会影响下一次运行，因此在运行新的图表类型之前应该进行选择。 图表选择下拉菜单 运行“颜色/色调自动”之前应选择图表类型。
		图表类型（用于下次颜色/色调自动运行）

自动区域检测

这也是选择自动或手动区域检测的好时机，该功能位于“颜色/色调自动”设置窗口的底部，并且对允许自动选项的图表启用（最初是Colorcheck和36 色块动态范围图表，未来会有更多）。

运行颜色/色调自动功能—要启动颜色/色调自动功能，请运行Imatest ，然后单击“颜色/色调自动”按钮。此时将打开一个窗口，供您选择文件（或一批文件）。

要计算时间噪声，请选择两个文件（用于 Imatest 推荐的差分法）或 4-16 个文件（用于 ISO 15739 方法）。计算详情请参见此处。

如果您选择了手动 ROI 检测，在选择文件后，Imatest 会检查图像大小是否与最近运行的图像大小相同（它会保存多种尺寸的图像）。如果大小相同，系统会询问您是否要重复选择相同的感兴趣区域 (ROI)：

如果图像大小与之前的图像不同，或者您点击“否，选择新的 ROI” ，则会弹出一个窗口，要求您选择区域。您可以通过在要分析的图表上从一个角到另一个角绘制一个矩形来完成此操作。不必担心区域是否完全精确——您可以对其进行微调。

初步（粗略）区域选择。在图表上画一个从一个角到另一个角的矩形。
图片来自Imaging-resource.com （来自单个相机评测示例页面的多目标）。

在粗略选择后打开的精细选择窗口中，对选择区域进行更精确的调整。不同图表的内部方框可能有所不同。（注意：如果您选择了“自动 ROI 检测”选项，并使用支持自动检测的图表进行确认，则会显示此窗口。）

• 整个 ROI 可以移动（^ > v <，左上）。
• 顶部、底部、左侧或右侧可以移动（T^ Tv R> R< B^ Bv L> L<，中间向左）。
• 可以单独移动四个角（四个角中左侧的 8 个按钮中的任何一个）。
• 您可以输入四个角点的像素值（ X(tl) 、 Y(br) 、…，其中tl代表左上角， br代表右下角，以此类推）。原点位于左上角。输入数值后请务必按回车键。
• 您可以选择精细、粗糙或超粗糙 (XC-25) 移动（每次点击移动 1、5 或 25 像素）。
• 显示内容可以缩小或放大。
• 可以调亮显示屏，以便更清楚地查看暗部区域。
• 对于某些图表（尤其是色块较大的图表），“失真”滑块左侧的“填充因子（线性）”滑块用于指定方块的相对大小。其默认值为 0.5。当镜头失真或图案对齐导致对齐困难时，可以使用较小的值。
• “失真”滑块允许分析高度失真的图像（桶形失真或枕形失真）。

完成微调后，单击窗口底部的按钮之一。如果单击“是，继续” ，则会打开如下所示的“颜色/色调自动”设置窗口。如果单击“是，继续”进入快速模式， “颜色/色调自动”功能将运行，显示选定的结果图，并保存选定的结果文件。

图表类型	选择图表类型。应用于下次运行。如果选择图表类型 3（最后灰度图）或 7（多行灰度阶梯图（非线性）），则应在下面的“特殊（多行）灰度图表类型”下拉菜单中选择具体的图表类型。
更多设置：颜色矩阵、噪点、镜像/旋转……	打开颜色/色调设置窗口，如下图所示。您可以选择颜色矩阵设置（详见颜色校正矩阵网页）、噪点设置、ISO感光度计算、mxn图表设置等，如下所述。
运行颜色矩阵	如果选中，则计算并应用颜色校正矩阵（CCM）。
参考	参考文件。可以是标准格式，也可以是读取格式（通常从 CSV 或 CGATS L*a*b* 或密度文件读取）。具体格式会因图表类型而略有不同。
色彩空间	色彩空间
噪声计算。	噪声计算。选择 1. 无（非视觉）噪声计算（最快），2. 基本噪声计算（较慢），或 3. 高级噪声计算（较慢）。
噪声和视觉噪声设置	打开“噪点和视觉噪点”窗口，具体说明请参见“颜色/色调交互式/自动/eSFR ISO 噪点” 。您可以在此选择视觉噪点和其他设置。
非均匀性校正	允许您使用在相同条件下拍摄的单独平场图像来校正非均匀照明。打开“非均匀性校正”窗口，该窗口在灰度和彩色图表模块的“非均匀性校正”部分中进行了描述。
特殊（多行）灰度图表类型	仅当选择图表类型 3（最后灰度图）或 7（多行灰度阶梯图（非线性））时可见。用于选择合适的灰度图表类型。
特殊灰度图表设置	打开一个窗口，允许您选择线性灰度阶梯图的密度增量。
在右侧显示缩略图和 EXIF 信息。	在图表右侧显示整幅图像和裁剪区域的缩略图以及 EXIF 结果。示例如下所示。
绘图设置（右侧）	选择输出数据。具体说明如下。

颜色校正矩阵	CCM 计算的设置说明请参见“颜色校正矩阵”页面。
事件 Lux	必须手动输入ISO感光度（曝光指数）计算所需的参数。光圈和曝光时间（秒）通常从EXIF数据中获取，但如果EXIF数据缺失，则可以手动输入。
噪音	设置说明请参见“颜色/色调/eSFR ISO 噪点”页面。
行、列 通用 MXN 图表	选择通用m x n （矩形）图表的行数和列数。选择此图表需要参考文件。
饱和度	输入图像的最大像素级别（对应于饱和度级别），用于对图像数据进行归一化以进行某些计算。 标准文件：255（或 65535...） ：饱和度级别会根据图像数据的数据类型和容器大小自动设置。这是默认设置。图像文件假定具有标准位深度（例如，8 位、16 位或 32 位数据）和标准饱和度级别。例如，对于标准的 8 位图像数据，饱和度级别将设置为 255。对于 16 位图像，饱和度级别将设置为 65535，而对于 32 位图像，饱和度级别将设置为 4294967295。 ITU-R 建议 601 (BT. 601: 235) ：饱和度级别设置为 235。 最大检测到的色块级别：饱和度级别设置为图像中色块区域检测到的最大值。如果图像数据的位深度不标准（例如，12 位数据存储在 16 位容器中），或者存在自定义饱和度级别，只要图像曝光足以使最亮的色块达到饱和状态，此功能就非常有用。 手动输入饱和度：饱和度级别设置为用户输入的值。如果图像数据的位深度不标准，或者存在自定义饱和度级别，则此功能非常有用。例如，对于存储在 16 位容器中的 12 位数据的图像，饱和度级别应输入 4095（2^12 - 1 = 4095）。
像素偏移	输入要从数据中减去的像素偏移量。像素偏移量并不罕见：它们会导致密度曲线过早趋于平缓。
非均匀性校正	允许您使用在相同条件下拍摄的单独平场图像来校正非均匀照明。打开“非均匀性校正”窗口，该窗口在灰度和彩色图表模块的“非均匀性校正”部分中进行了描述。
图像方向	（适用于下次读取）选择标准图像方向、镜像（水平翻转）、镜像（垂直翻转）、旋转 180 度。

结果数据

1. 3D 色差（带分割）

在此图中，区域的高度代表选定的颜色差异，在本例中为 ΔE* _ab （即 Delta-E）。色块平台的顶部以双色显示，左上角为参考颜色，右下角为实际输入颜色。此图可用于比较测量颜色与感知颜色差异。（它们可能与理论声称的匹配度不完全一致。）

此图表右侧会显示缩略图和 EXIF 数据（在“颜色/色调自动设置”窗口中勾选复选框即可设置）。其他图表将不显示这些结果，即未勾选该复选框（这样可以节省空间）。

2. 分割颜色（参考/输入）图 分割颜色图显示左上角的参考（理想）颜色和右下角的输入颜色。 如果已计算颜色校正矩阵（如果已选中复选框），则此图以及 3D 颜色差异图（上图）将在左上角显示参考颜色，在右上角显示输入颜色，在底部显示校正后的颜色。 3D色彩差异细节， 计算颜色校正矩阵
3. 二维 a*b* 图 显示 L*a*b* 色彩空间的 a*b* 平面。色度差异（非常）近似于参考值和相机值之间的距离。（此差异为 ΔC <sub>ab</sub> 。更复杂的 ΔC<sub> 94</sub>和 ΔC<sub> 00 </sub> (CIEDE 2000) 方程（此处有描述）更为精确。） 如果已计算出颜色校正矩阵，则会显示校正后的值。
4. XY色度 这张图虽然很常见，但与上面的a*b*图相比，在视觉上不够均匀。绿色在这张图中占据的面积过大。 如果已计算出颜色校正矩阵，则会显示校正后的值。
5. 黑白密度和白平衡 上图显示 Log(像素级别/255)（最大值为 1）与输入密度（-log 10 （曝光））的关系，即使用密度单位。 下图展示了几种不同色块密度下的ΔC值。参见颜色检查附录。 如果已计算出颜色校正矩阵，则会显示校正后的值。
6. EXIF 数据和颜色矩阵 该图显示了选定的 EXIF 数据和颜色矩阵校正结果，包括 颜色矩阵 用于计算矩阵的设置说明（用于优化的颜色差异、加权、线性化等） 输入图像与参考图像之间以及校正图像与参考图像之间的平均颜色差异和最大颜色差异。
7. 附加二维彩色图 此处显示矢量示波器界面。您可以在此处选择几个图表之一： u'v' 色度 矢量示波器 2D CbCr（源自 YCbCr） 来自 HSV 的 HS（色调-饱和度） 来自 HSL 的 HS（色相-卫星） 这些显示方式在“使用颜色/色调 - 显示和选项”中有详细说明。
噪声/信噪比分析（并非所有图表都适用） 噪声/信噪比分析仅适用于图像块足够大、能够提供良好噪声统计数据的图表。噪声分析包括标准像素噪声、色度噪声、场景参考噪声、传感器（原始）噪声和 ISO-15739 视觉噪声。信噪比 (SNR) 可以以比值或分贝 (dB) 的形式显示。 本页所示的 ColorChecker SG 色块太小，但幸运的是，Imaging-Resource 图像在 SG 的左侧有一个标准的 24 色块 ColorChecker，我们对其进行了分析，从而得到了右侧所示的结果。 噪声分析在“颜色/色调”和“eSFR ISO 噪声”部分有详细描述。ISO 15739 视觉噪声已添加到Imatest 4.0中。 可供选择的选项如下。 噪声与输入密度（RGB） 像素噪声或最大像素级别的百分比 信号/噪声 (S/N) 与输入密度 (RGBY) 亮度 (Y 通道) 用于 S。 SNR (dB) 与输入密度 (RGBY) SNR (dB) = 20 log 10 (S/N)。 如右上方所示。 色度噪声与输入密度 色度信噪比与输入密度的关系 色度信噪比（dB）与输入密度的关系 CIELAB (L*a*b*)噪声 CIELAB (L*a*b*) 信噪比 CIELAB (L*a*b*) 信噪比 (dB) 噪声与像素（所有图像块）这些测量结果对于表征原始（未经处理或仅经过少量处理）图像中的传感器性能至关重要。 信噪比与像素（所有色块） 信噪比（dB）与像素（所有图像块）的关系 光圈（场景参考）噪声和动态范围 光圈（场景参考）信噪比和动态范围。动态范围级别以粗水平线（黄色、橙色等）显示。 如右图所示。 光圈（场景参考）信噪比（dB）和动态范围 ISO 15739 视觉噪声 (L*u*v*) ISO 15739 视觉信噪比 (L*u*v*) 以分数表示 ISO 15739 视觉信噪比 dB (L*u*v*) 分贝 (dB) = 20*log 10 (分数)