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 (typically C:\Program files\Imatest\Imatest in win32 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.

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.

Font size/DPI scaling If DPI scaling is set to Larger scale (120 DPI), buttons at the top and the right of the Imatest main window may be truncated. This problem should be fixed with Imatest 3.2.1. In earlier versions there are two fixes. 1. In the Imatest main window, click Settings (on the top bar), Enlarge screen. 2. (In Vista) Right-click on the wallpaper, click on Personalize, then click on Adjust Font size (DPI) (near the top of the left bar) to open the DPI scaling window. Select Default scale (96 dpi) instead of Larger scale (120 dpi). Reboot for the change to take effect.

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), 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 and custom RAW files using Generalized Read Raw. New cameras are typically added to dcraw within a month or two of their introduction. The dcraw page has the latest list of cameras.

Multiple file read In Imatest Master you can select several files to read. Depending on how you respond to the multi-image dialog box (below), The files can be analyzed individually in sequence (batch mode), or The files can be combined— averaged— and the mean analyzed (it can also be saved). This is useful for measuring sensor fixed pattern noise in Stepchart, Colorcheck, and Light Falloff and in SFR for measuring performance of image stabilization. The files should be in the same folder, have the same pixel dimensions, and be framed identically. If you choose Combine files, you'll have the option of saving the combined file with 16-bit TIFF format as default. Batch mode is not supported in Rescharts. The saved file name is the same as the first selected file name with _comb_n appended, where n is the number of combined files.

• 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.) Figures can be saved as PNG (losslessly-compressed) image files or Matlab Fig files, which can be opened and manipulated with Open Fig file.

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: You can select normal raw conversion (with demosaicing) or 8 or 16-bit Bayer raw (RGRGRG, GBGBGB, ... sequence; undemosaiced). The latter formats allow several Imatest Master modules to examine the unprocessed pixels. Choices: Demosaicing Normal RAW conversion (demosaiced) RAW 8-bit (Bayer RAW; no demosaicing) RAW 16-bit (Bayer RAW; no demosaicing) You can choose among three conversion programs (all based on dcraw). Program dcraw The original; may not work in Vista LibRaw dcraw emulator (works in Vista; no Bayer RAW) dcrawMS Works in Vista 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.

Miscellaneous controls and utilities

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.

EXIF displays EXIF data for an image file. Most file formats supported when ExifTool is installed. Exif data can be saved in a text file in the same folder as the image for viewing/searching with the Save Exif data button.

Exif viewer

Open Fig file opens a Matlab Fig file saved during an Imatest module run. Unlike image files, Fig files can be manipulated— most importantly, 3D Fig files can be rotated for enhanced visualization. But Fig files should be used sparingly because they can be as large as several megabytes.

Saved settings:  Imatest saves a number of settings, including Font size, folders for opening and saving images, plot selection, and figures to save. To view or edit the settings, click the Settings menu (in the toolbar on the top of the Imatest window), then click View settings (ini file) or Edit/Reset modules. To restore these settings to their original defaults, click (in the toolbar on the top of the Imatest window), then click Reset defaults (all) in the Settings menu. The settings are stored in imatest.ini.

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

Options I

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

Expert vs. Basic mode  affects the complexity of input dialog boxes. Basic (beginner) mode uses a simplified dialog box and uses defaults for settings that are not displayed. Modules are gradually being added.

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  Cropping options. You can select whether to ask for cropping and whether to use the last crop (for same-sized images). For Colorcheck you can also choose between traditional automatic patch detection and Multicharts-like patch detection, where all squares are shown in the fine adjustment window.

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 and memory) 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 II

Options 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.

EXIF data acquisition  This selects the program used to read EXIF data: image file metadata that contains camera and lens settings. Selected EXIF data (important values such as aperture, exposure time, ISO speed, and focal length) is displayed in several figures and EXIF data is saved in CSV and XML output files. There are four settings:

Setting 1, jhead.exe, is the default. Jhead is a compact program with limited capabilities included in the Imatest installation file. It only works with JPEG files, and it captures limited EXIF data. Settings 2 and 3 (ExifTool; introduced with Imatest 3.2.1) work with virtually any file type and capture virtually all available EXIF data. If the setting 3 (save ALL EXIF) is selected, all the EXIF data— a huge amount; some quite obscure— is written to the CSV output files.

The second and third settings require that ExifTool be downloaded and installed.

• Go to the ExifTool home page and download the Windows standalone executable (a zip file). This file is not included in the Imatest installation because it is frequently updated.
• In Windows Explorer, double-click on the downloaded zip file.
• Copy the contents ( exiftool(-k).exe ) to the Imatest installation folder (typically C:\Program files\Imatest\Imatest in win32 English-language installations for Imatest 3.6+).
• Rename exiftool(-k).exe to exiftool.exe.

The final selection is for very 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

Special user code  enables custom features for specific users. Normally blank.

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 .

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

Dropdown menus

Dropdown menus are located at the top of the Imatest main window. Most items duplicate the controls elsewhere in the window, but some are unique.

File contains DOS command, selections for viewing or copying the current or previous session, Clear Memory, Close Figures, and Exit. DOS command lets you execute a DOS command through Imatest. Tthe session commands are useful for debugging, as described in Troubleshooting. Clear Memory removes the image data stored after running SFR. This may release enough memory to speed up memory-intensive modules, such as Light Falloff.

Modules opens Imatest analysis modules. The entries duplicate the buttons on the left of the Imatest main window.

Utility opens Imatest utility modules. The entries duplicate many of the buttons on the right of the Imatest main window.

Settings contains functions that control various aspects of Imatest operation.

• 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.
• Save Settings copies settings from imatest.ini (which stored the current, active settings) to a named file (with extension ini). Particularly useful for saving regions of interest (ROIs) for SFR runs and for controlling Imatest API modules. The most recent folder used to save or retrieve settings is displayed in the file selection dialog box, but any folder may be selected.
• Load Settings retrieves settings from a named file (with extension ini) and stores them in imatest.ini.  It is useful for restoring ROIs or for restoring settings after they have been reset. The most recent folder used to save or retrieve settings is displayed in the file selection dialog box, but any folder may be selected.
• 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 may interfere with some Imatest operations.
• Reset defaults restores settings to their default values by resetting imatest.ini. On rare occasions this clears bugs. See Troubleshooting. It is a good idea to save settings prior to resetting them.
• Edit/reset module(s) opens a special editor that allows ini file values to be examined and entire sections to be deleted if the corresponding module crashes. Described in Troubleshooting.
• Options and settings I and II contain settings that affect SFR ROI (region of interest) error checking, Stepchart ROI selection, and folder names for storing results, and more.
• DOS command allows you to enter a DOS command while Imatest is running. Useful for troubleshooting, for example, for diagnosing path issues.
• When checked, Fixed sharpening radius keeps the SFR standardized sharpening radius fixed, even for edges with poor MTF where it would otherwise automatically increase.
• IT options sets several options for controlling IT (Industrial Testing) runs.
• Enlarge 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.

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 are used to register Imatest.
• About displays the Imatest version and user registration information.
• Check for updates opens a web page that shows the latest version.
• Welcome window displays the window that normally appears when Imatest is started in evaluation model.
• Several additional web pages, including this one, are included.

Figures

Imatest figure: You can resize it or zoom in on individual plots.
The toolbar for Imatest 3.6+ , which includes Data cursor ,
is shown.

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

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.

Toolbar for Imatest 3.5.1 & earlier

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. Imatest allows you to save figures as PNG files— an excellent format with lossless compression— or as Matlab fig files, which can be manipulated, but which require much more storage (not recommended).

Of the remaining icons, Zoom in: is particularly useful. 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 inside the image restores the full unzoomed image.

   Data cursor example

Imatest 3.6+ includes an extremely useful function called Data Cursor, selected on by the toolbar icon. When selected, you can click on a curve and display its coordinates in a small box called a Datatip. Right-clicking on the Datatip lets you can delete it or choose additional options.

In most modules, figures can be saved as either PNG files (a standard losslessly-compressed image file format) or as Matlab FIG files, which can be opened by the Open Fig file button in the Imatest main window. Fig files can be manipulated (zoomed and rotated), but they tend to require more storage than PNG files, especially for 3D files, which can be generated by SFRplus and Light Falloff. In general, PNG files are preferred unless significant manipulation will be required at a later time— for example if you wish to rotate 3D files (which can be several megabytes).

.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 Install and use the Software on a single workstation used non-simultaneously by one or more people. This 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,