Tour of Imatest

Imatest™ is a suite of programs for measuring the sharpness and image quality of lenses, digital cameras, digitized film images, and prints using inexpensive, widely available targets. It is available in two versions:

• Imatest Light, with everything an individual photographer needs to test cameras, lenses, and printers. $199.
• Imatest Pro, the full-featured version for professionals and imaging system developers. $599. Learn more about the versions. Batch mode (multiple input files) is available for SFR, Colorcheck, Stepchart, Light Falloff, and Distortion.

Imatest consists of several modules, each of which analyzes images of one or more test charts. Image files can be in any of several standard formats (TIF, high quality JPEG, PNG, etc.). Imatest Pro also analyzes Bayer RAW files. A Test chart Cross-reference follows.

	SFR  measures the sharpness of cameras and lenses using a simple slanted-edge target (either the industry-standard ISO 12233 chart or a target you can print yourself on a high quality inkjet printer). Its standardized sharpening algorithm allows you to compare digital cameras on a fair basis. It also analyzes Chromatic Aberration and noise and calculates the Subjective Quality Factor (SQF)— a measurement of how sharp a print of a given size will appear, based on MTF and the eye's Contrast Sensitivity Function (CSF). It can analyze regions as small as 10x10 pixels.
	MTF Compare (Imatest Pro only) is a post-processor for Imatest SFR that compares the MTFs of different cameras, lenses, and imaging systems using saved data from CSV files. These comparisions are far more detailed than comparisions of MTF50 or other summary results.
	Colorcheck  measures a camera's color quality, tonal response, exposure accuracy, and noise using the GretagMacbethTM ColorChecker®, which is available from Adorama and other sources.
	Stepchart  measures a camera's tonal response, noise, and dynamic range using grayscale step charts from Kodak (the Q-13/Q-14), Jessops, or Danes-Picta (Czech Republic), or transmission step wedges from Stouffer, Danes-Picta, or Kodak. It also measures exposure accuracy and veiling glare (susceptibility to lens flare) with reflection step charts. It also works with several charts (some ISO standards) from Applied Image. The Dynamic Range postprocesser for Stepchart, measures dynamic range from Stepchart results for several differently-exposed stepchart images.
	Multicharts analyzes several color charts for tonal response and color accuracy using a highly interactive interface. It also analyzes grayscale charts for tonal response. It currently supports the standard 24-patch GretagMacbethTM ColorChecker® and the IT8.7 in Imatest Light and Pro and the ColorChecker SG, several linear grayscale stepcharts, and patterns of squares arranged on a circle (for analyzing custom "pie" charts) in Imatest Pro.
	Print Test  measures the quality (color response, color gamut, tonal response, and Dmax) of printers, inks, paper, ICC profiles, and rendering intents. A version of Print Test with additional capabilities is included in Gamutvision.
	Light Falloff (Uniformity) measures the light falloff (vignetting) of lenses. In Imatest Pro it also measures several types of image sensor nonuniformity, including color shading, detailed noise distribution, and medium-sized (visible) nonuniformities, inculding dust smudges. It also flags stuck (dead and hot) pixels. A histogram display makes it easy to select dead/hot pixel thresholds. Display options include contours superposed over images and pseudocolor with color bar.
	Distortion measures lens distortion and calculates coefficients for correcting it using a square or rectangular grid that can be printed from files created by Test Charts.
	Rescharts analyzes several resolution-related test charts using a highly interactive interface. Functions include Slanted-edge SFR, which largely duplicates the calculations in SFR, Log frequency, which measures MTF and color moiré using a chart that varies in spatial frequency, and Log frequency-contrast (Imatest Pro only), which measures MTF and loss in fine detail due to software noise reduction using a chart that varies in spatial frequency on one axis and contrast on the other.
	Test Charts creates image files for printing test charts on high quality inkjet printers. Charts include SFR slanted-edge images, star charts, patterns with varying spatial frequency and contrast, and zone plates. Several patterns can be used for observing aliasing, Color Moire, detail lost to software noise reduction, and other phenomena. Numerous options are available, including contrast ratio, highlight color, and sine or bar pattern (for certain charts). Both bitmap and Scalable Vector Graphics (SVG) charts, which can be printed any size without loss of quality, are available.
	Concise instructions for testing lenses using Imatest SFR.
	Gamutvision is a standalone program (sold separately from Imatest) for exploring the behavior of color management, gamut mapping, and rendering intents, incorporating Print Test. See precisely how gamut mapping affects colors. Assess ICC profile quality. Learn how working color space affects print quality. Determine the capabilities of printers and papers using downloaded ICC profiles. Compare them with scanned prints from your own printer. And much more...

Imatest is frequently updated. Major releases are announced on the Imatest main page. All releases are described in detail in the Change Log. You can download and install a new version at any time without uninstalling the old version.

Imatest is written in compiled Matlab, Release 13 (Version 6.5.1), an outstanding language for solving engineering problems. Algorithms can be rapidly coded and modified in response to user requests. It is a standalone program; Matlab does not need to be installed, but the Matlab runtime library needs to be downloaded and installed once (the first time Imatest is installed). In most cases this is done automatically.

Requirements:  Windows 2000, 2003, XP, Vista, or later, or Macintosh computers with Virtual PC 6 or 7. Minimum RAM is 256 MB (512 MB recommended), and minimum screen size is 1024x768 pixels.

Supported input file formats:  TIFF, PNG, or PPM (all 24 or 48-bit), JPEG, BMP, GIF, HDF, PCX, XWD, as well as RAW files from most digital cameras, using Dave Coffin's dcraw.

Imatest output is optionally written to two types of file: .CSV (comma-separated variable; Excel-readable), and XML.

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

Test chart cross-reference

The table below lists commercially-available charts. Additional charts that you can print a high quality inkjet printer are described in Test Charts. Cross references contains this material sorted by quality factor and module.

Try Imatest

You can download an evaluation version that allows you to make up to 20 runs of the individual modules. It has all the capabilities of the full versions except that (1) you can't save results, and (2) a watermark appears in the background of the figures.

You may purchase Imatest at any time by from Regsoft.com's secure site by going to the purchase page. The price includes one year of updates. You may also purchase Imatest via wire transfer or custom Paypal invoice. You can register Imatest as soon as the purchase is complete. Details can be found on Installing Imatest and getting started.

Learn more about Imatest

All Imatest documentation is available online. The Documentation page contains the table of contents, and the Cross-reference indexes image quality factors, modules, and test charts. The FAQ answers many questions.

Many of the concepts used by Imatest to measure sharpness and image quality are new to photographers and require some study. Sharpness: What is it and how is it measured? is a good place to start. It outlines the basic principles behind SFR. Standardized sharpening: why it's needed for comparing cameras, Chromatic aberration, and Subjective Quality Factor (SQF) contain additional concepts. Shannon information capacity is a relatively new concept for imaging, still under development— its measurement is distorted by ubiquitous software noise reduction.

Using Imatest contains instructions that are common to all modules. Instructions for SFR, Colorcheck, Stepchart, Print test, and additional modules are on individual pages.

Many of the terms used in the documentation are defined in the Glossary.

An Imatest forum has been established for posting questions and responses. The Change Log describes the Imatest version.

The Imatest license

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. The full license may be viewed here.

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 the explicit permission of Imatest LLC. Contact us to learn more.

Imatest LLC assumes no legal liability for the contents of published reviews. If you plan to publish test results, you should take care to use good technique. See Using Imatest for more details.

Links

Volker Gilbert has written an excellent French language description of Imatest. (PDF version)