Using Imatest

Running Imatest

Imatest is opened by double-clicking the Imatest icon  on

• the Desktop,
• the Windows Start menu ( Start → All Programs →Imatest → Imatest ),
• or the Imatest directory (usually C:\Program files\Imatest in English language installations).

To run Imatest in Windows Vista, you'll need version 2.3.3 or later.

After several seconds, the Imatest main window, shown below, opens. Imatest modules are run by clicking on one of the buttons on the left. Instructions for the individual modules are on their own pages, listed below. Click here for the documentation Table of contents.

SFR MTF Compare Rescharts Colorcheck Multicharts Stepchart Light Falloff Dynamic Range Distortion Print Test Test Charts Screen Patterns dcraw | Rawview

Imatest main window

When you first install Imatest it operates in evaluation mode, which allows 20 runs and does not allow data to be saved. A welcome page summarizing Imatest's capabilities and operations is displayed when Imatest is started in evaluation mode. To continue using Imatest you must purchase and register it.

The following steps are typical for most Imatest modules.

• Open the image file. A dialog box requests the name of the input image file. Imatest supports TIFF (24 or 48-bit; without LZW compression), JPEG, PNG (24 or 48-bit), BMP, HDF, PCX, XWD, and PPM (24 or 28-bit) file formats. It also supports RAW files for a large variety of digital cameras, using Dave Coffin's dcraw. New cameras are typically added to dcraw within a month or two of their introduction. The dcraw page has the latest list of cameras.
• Cropping/Region of Interest (ROI) options  can be set by clicking Options & settings... in the main Imatest window. The relevant portion of the dialog box is shown below.

ROI (region of interest) cropping and repeat options

The recommended setting for Colorcheck, Distortion, and Light Falloff (Uniformity) is Select crop by dragging cursor. Ask to repeat crop for same-sized image. Other settings (no cropping... or do not ask to repeat crop...) are included for backward compatibility. If Automatic (for Stepchart ROI) is unchecked, you must specify the number of patches (zones) in the crop.

• Crop the image. When an input image with a different size from the previous run (of the same module) is opened, the entire image is displayed, and the message, Select the ROI by clicking & dragging, or click outside the image, appears above the image. Select the crop area (Region of Interest) by clicking on an intended corner and dragging the mouse to another corner. If you don't want to crop the image— if you want to use the entire original image, click outside the image. Note: the Zoom does not work during region selection. Imatest mistakenly assumes you are trying to select the entire image. To enlarge the image (to view the crop area more clearly), maximize it by clicking on the square next to the upper right corner of the Window. After you click OK, a fine adjustment dialog box (shown below) appears.
• Use previous crop? When an input image with the same size as the previous run is opened, an image of the image showing the crop is displayed along with the following dialog box.

ROI repeat selection

• Fine adjustment.  After the rough crop has been made, a fine adjustment dialog window opens.

ROI fine adjustment dialog box for several modules.

The buttons in the box on the upper-left move the entire ROI up, down, left, or right. The buttons in the middle-left move the individual edges. The Fine radio button (move one pixel per click) is selected when the fine adjustment window opens. Other selections are Coarse (5 pixels per click) or XC-25 (Extra Coarse; 25 pixels per click). You may also select the L, R, T, or B edge locations. The fine adjustment window for Multicharts and Stepchart (with manual ROI selection) is slightly different: it displays squares for individual patches, and it allows individual corners to be adjusted.

• Enter additional input data. Unless Express mode has been selected, a dialog box opens that requests the title (which defaults to the file name) and other data, depending on the module. Most additional data is optional (most is saved from previous runs); you only need to pay attention to settings you wish to change. Click OK to continue or Cancel to terminate the run.
• Run the program by clicking OK. The results are presented in individual Figures.
• Save results? A dialog box asks if you would like to save the results. Checkboxes in the dialog box enable you to select the Figures and .CSV (Excel-readable) and XML files to be saved. You may examine the results before deciding which, if any, to save. (The Save box is omitted in the evaluation version.)

About RAW files RAW files are the unprocessed output of digital image sensors. For Bayer sensors, each RAW pixel represents a single color in RGRGRG, GBGBGB, ... sequence. To be converted into usable, standard file formats (TIFF, JPEG, etc.), raw files must be processed by a RAW converter. RAW converters perform several functions: demosaicing (converting the Bayer sequence into full color), applying a gamma curve, often with an additional tonal response curve, reducing noise, and sharpening the image. These operations can affect Imatest's measurements, especially SFR. More detail can be found in RAW files.

dcraw input dialog box

The best way to be sure an image file faithfully resembles the RAW file— that it has a pure gamma curve, no sharpening, and no noise reduction— is to read a RAW file into Imatest and convert it into a standard format (typically TIFF) using Dave Coffin's dcraw. If you select any of the standard RAW formats (CRW, NEF, etc.) or if a file that contains RAW data (e.g., Phase One TIF) is detected the dialog box on the right appears. It allows you to choose among several RAW conversion options. dcraw conversion details: The Processing box allows you to select normal raw conversion (with demosaicing) or 8 or 16-bit Bayer raw (RGRGRG, GBGBGB, ... sequence; undemosaiced). The latter formats allow several Imatest Pro modules to examine the unprocessed pixels. Choices: Normal RAW conversion (demosaiced) RAW 8-bit (Bayer RAW; no demosaicing) RAW 16-bit (Bayer RAW; no demosaicing) The following output color spaces are available for demosaiced output. RAW (not true RAW pixels): Demosaiced with no color space conversion or White Balance. The camera's color profile is needed to correctly interpret the colors. Gamma = 0.45. sRGB, Adobe RGB (1998), Wide Gamut RGB, ProPhoto RGB, and XYZ. Profile tags are embedded in the output file for the four standard color spaces. For 24-bit conversion, gamma appears to be fixed at 0.45, independent of the output color space. (It should be different for ProPhoto, which is designed for display at gamma = 1.8.) For 48-bit conversion gamma is fixed at 1 (linear conversion; does not correspond to standard color spaces). Auto-exposure is always applied for 24-bit conversion (but not for 48-bit). I've changed the default to make it slightly darker than the dcraw default (using -b 0.99 in the command line) to reduce the likelihood of clipping pixels. For now we're stuck with auto-exposure for 24-bit conversion: see dcraw Frequently Asked Questions. Dcraw converts RAW files into TIFF files. (The obscure PPM format is available as an option.) If check the box to delete the converted (TIFF) file, you may save the image in one of two compressed formats: PNG (lossless compression; takes longer) or JPEG (lossy compression; maximum quality; 24-bit only). A list of supported cameras appears on the dcraw site. New cameras are typically added within one to three months of their introduction. The dcraw version included with Imatest sometimes falls behind. According to Dave Coffin, "Francisco Montilla provides Mac OS and Windows executables on his website. And Benjamin Lebsanft has volunteered to maintain Windows executables optimized for specific CPUs." Dcraw does not currently run on Windows Vista. According to the dcraw FAQ, it should work when Service Pack 1 (SP1) is released.

Other controls

Exit closes all figures and terminates Imatest.

Close figures closes all figures. You can close figures individually by the usual Windows methods — clicking the X in the upper right or right-clicking on the figure icon on the Taskbar and selecting Close.

Saved settings:  Imatest saves a number of settings, including Font size, folders for opening and saving images (for all modules), plot selection (for SFR), and save figure selection (for SFR and Colorcheck). To restore these settings to their original defaults, click the Settings menu (in the toolbar on the top of the Imatest window), then click Reset defaults, Yes. The settings are stored in Imatest.ini.

Options & settings I... and Options & settings II... (at the bottom of the Imatest main window to the left of the Fonts menu); also in the Settings dropdown menu) opens the boxes shown below, which allow several options to be specified.

Options & Settings I

Options and Settings I for setting ROI options, Large file processing, and Batch run order.

ROI (Region of Interest) section controls cropping options.

• SFR ROI filtering  When Light filtering is checked the tests that validate the SFR ROI (region of interest) are relaxed. This can be useful when testing noisy images, rough edges, images of endoscopes or other devices with interfering patterns, but it can lead to errors if regions are selected carelessly. Normal filtering is the default.
• Stepchart ROI selection  Automatic selection (the default) can be toggled. If it is turned off, a fixed number of patches (6-41) can be selected for Stepchart analysis. This option is useful when high noise in dark regions confuses the automatic ROI detection.
• Colorcheck, Distortion, Light Falloff  Allows the cropping options to be selected. You can select whether to ask for cropping and whether to use the last crop (for same-sized images).
• LARGE FILES (Light Falloff, Distortion)  These two modules typically use little or no cropping. As a result, memory may sometimes overflow. This setting offers the option of cutting the image dimensions in half (1/4x in area) to avoid memory problems.

Batch run order  The actual order of batch runs may differ from the order of selection in curious ways that depend on the operating system or other factors. With one of the choices in this popup menu the run and selection orders should be the same.

Reset restores defaults: it sets SFR ROI filtering to Normal, Stepchart ROI selection to Automatic, turns off all global folder settings, and checks Get EXIF data .

Options & Settings II

Options and Settings II for setting folder options, SFR save file suffix, etc.

Global folders  The default folders for opening files and saving results can be set globally using the second group of controls. Normally (with Global folder for opening files unchecked), the default folder for opening files is changed only for the Imatest module in use: one module at a time. When it is checked, the default folder for opening files is changed for all modules. This can be convenient if project data for several modules is stored in the same file.

When either of the Global folder for saving results... radio buttons is set, the default save folder is changed for all modules whenever the input folders are changed.

Get EXIF data (normally checked)  If checked, EXIF data is read for JPEG images. Should be unchecked in rare cases (e.g., industrial prototypes with non-standard EXIF data) that cause the EXIF read routine to crash.

Suffix for saved SFR plots and CSV and XML files  Normally the root name (input or selected file name ) is followed by the channel, ROI orientation (AL = above left (relative to the center), etc.) and distance from the center in percentage of distance to the corner. Example: rootname_YAL79_MTF.png for the Edge/MTF plot. An alternative can be selected where _ROI_ followed by the ROI number nn is used in place of the orientation and distance. Example: rootname_ROI_03_MTF.png

Reset restores defaults: it sets SFR ROI filtering to Normal, Stepchart ROI selection to Automatic, turns off all global folder settings, and checks Get EXIF data .

Save settings... saves the current settings (stored in imatest.ini) in a named file. It is particularly useful for saving regions of interest (ROIs) for SFR runs. The most recent folder used to save or retrieve settings is displayed in the file selection dialog box, but any folder may be selected.

Retrieve settings... retrieves saved settings, which are stored in .ini files. (It copies the selected .ini file to imatest.ini.) It is useful for restoring ROIs. The most recent folder used to save or retrieve settings is displayed in the file selection dialog box, but any folder may be selected.

Expand hi res figs applies only to high resolution screens (1600x1200 pixels and above). When this box is checked (by default), images are enlarged so they don't look tiny on the screen. Unchecking the box turns this feature off. Images are smaller but better suited for website presentation. The setting is saved between runs.

Small / Normal / Large fonts alters the font size in output figures and GUI windows. The default is Normal. The setting is saved between runs. This address problems with tiny fonts in high resolution screens (1600x1200 pixels and above) or larger than expected fonts which appear when the video card DPI setting is Large size (120 DPI) instead of Normal. The video card setting can be accessed by right-clicking on the Windows background, then clicking Properties, Settings, Advanced, General (tab). Large fonts are displayed if DPI is set to Large size (120 DPI). 96 DPI is normal. Windows may need to be rebooted before new settings take effect.

Help opens a relevant web page on computers connected to the Internet.

Pulldown menus

Pulldown menus are located at the top of the Imatest main window. Most items duplicate the controls listed above, but a few are unique.

File contains Clear Memory, Close Figures, and Exit. Clear Memory has no corresponding control button. It removes the image data stored after running SFR. This may release enough memory to speed up other modules, such as Light Falloff, which can use large amounts of memory.

Modules opens the Imatest modules. The entries duplicate the column of buttons on the left.

Settings contains several functions that control various aspects of Imatest operation.

• Save Settings copies settings from imatest.ini to a named file (with extension ini). Particularly useful for controlling Imatest API modules.
• Retrieve Settings retrieves settings from a named file (with extension ini) and stores them in imatest.ini. 
• View Settings displays the settings— the contents of imatest.ini— in the Notepad viewer. You can edit this file (with care!) and save it as a named file if desired. You can send us the contents of imatest.ini for help with troubleshooting. The Notepad window should be closed when you are finished viewing it: it can interfere with some Imatest operations.
• Default Settings has no corresponding control button. It restores settings to their default values by reinitializing imatest.ini. On rare occasions this clears bugs.
• Options and settings contains settings that affect SFR ROI (region of interest) error checking, Stepchart ROI selection, and folder names for storing results.
• When checked, Fixed sharpening radius keeps the SFR standardized sharpening radius fixed, even for edges with poor MTF where it would otherwise automatically increase.
• API options sets several options for controlling API runs.

Help contains Online Help, Register, Register Upgrade, and About, and Welcome window.

• Online Help corresponds to the Help button; it opens a browser window.
• Register and Register Upgrade is used to register Imatest.
• About displays the Imatest version and user registration information.
• Welcome window displays the window that normally appears when Imatest is started in evaluation model.

Figures

Imatest results are displayed in individual windows called figures. A typical figure— the result of running SFR for the Canon EOS-10D— is shown below.

Figures may be resized, minimized, maximized, or closed using standard Windows operations. In addition, several Windows and Matlab-specific operation can be found in the toolbar at the top of the image. The first four icons in the toolbar are standard Windows icons: New file, Open, Save, and Print. Open and Save refer to Matlab .fig figures, which can only be opened from the Matlab program or a Matlab figure window. Imatest allows you to save figures as PNG files— an excellent format with lossless compression. Of the remaining three icons, the most useful is Zoom in: . Clicking on it highlights it and enables you to zoom in on regions of the plots. You can click and drag to create a zoom rectangle or you can click on any point to zoom in on that point. Double-clicking anywhere on the image restores the magnification to its initial state

Imatest figure: You can resize it or zoom in on individual plots.

Two precautions when working with Figures

To see Figure resource use, open the Windows Task Manager. In Windows XP, click Control-Alt-Del or right-click in the Taskbar, usually at the bottom of the screen. Click on the Processes tab, then click CPU twice so the tasks with the most CPU usage appear at the top. Imatest can be a real CPU hog when several Figures are open; CPU use appears to increase with the square of the open Figures. On my dual 1 GHz Pentium Windows XP machine, 8 open Figures use 6% of the CPU; 16 open Figures use 33%. Over 20 would seriously slow the computations.

.CSV and XML output files

Individual Imatest modules can optionally write two types of output file, which contain most of the results. They may, if desired, be entered into other programs. .CSV files are most often displayed with Microsoft Excel. XML files can be used as input to database programs and for additional applications yet to be developed. They can be displayed in somewhat readable form with any web browser. Please contact us if you have requests or suggestions about Imatest output. Note: These files are not saved in evaluation mode.

CSV files– Excel-readable Comma-Separated Variable format. Here is an example of typical output.

Module,Colorcheck
File,Canon_EOS10d_ColorCheck_lt_small.jpg
Run date,31-Dec-2005 18:11:00

Zone,Gray,Pixel,Pixel/255,Px/255 ideal,Log(exp),Log(px/255),WB Err Deg,WB Err Mired
19, 1, 241.6, 0.9475, 0.9569, -0.050, -0.023, 163, -3.8
20, 2, 215.8, 0.8464, 0.7922, -0.230, -0.072, 491, -10.8
21, 3, 179.0, 0.7020, 0.6353, -0.440, -0.154, 450, -10.0

The same data displayed in Excel looks like this.

XML files– Similar output to the .CSV data above is shown below, displayed in the Firefox browser, which formats the results slightly (adds indentation and colors). XML output was introduced with Imatest 1.6.4. It will be refined in succeeding releases.

Use of Imatest

The Imatest license for Light and Pro allows an individual user to register and use the software on (A) a maximum of three computers (for example, home, laptop, and office) used exclusively by a single individual, or (B) a single workstation used nonsimultaneously by multiple people, but not both. It is not a concurrent use license.

License holders are encouraged to publish test results in printed publications, websites, and discussion forums, provided they include links to www.imatest.com. The use of the Imatest Logo is encouraged. However you may not use Imatest for advertising or product promotion without explicit permission from Imatest LLC. Contact us if you have questions. The full text of the license can be found here.

Imatest LLC assumes no legal liability for the contents of published reviews. If you plan to publish test results, especially for MTF, you should take care to use good technique. Considerations include,