Imatest 4.4+ can evaluate auto-focus (AF) as a measure of MTF with respect to time. This can be performed by using the SFR module with an appropriate video file. Uses/Purpose This metric is intended to be used as a way to measure the time a camera system takes to auto-focus. Rise time and settling time are automatically calculated. This measurement does not provide information about the accuracy or precision of auto-focus. To evaluate those measures, several measurements should be performed on the final, settled images and compared. File Selection and Frame Selection Begin by clicking on SFR from the main window and select a […]

Analyses & Output – INI settings – Chart Definition Files – Chart Definition Utility   INI file fields relevant to Arbitrary Charts The following INI fields are currently exposed to the user to control the behavior of the Arbitrary Charts module and its output. They have been organized here by topic, but do not need to be in any particular order or grouping in your INI file itself.    [arbcharts] section Slanted-edge Analysis     Texture Analysis   Star Analysis   Wedge Analysis   Uniformity Grid Analysis   Color/Tone/Noise   Perceptual metrics   Module operation and misc.   [api] section   […]

Analyses & Output – INI settings – Chart Definition Files – Chart Definition Utility   Data outputs from the Arbitrary Charts Module are different from other modules in Imatest: Only JSON files are output, not CSV or XML. The structure of JSON is substantially different than other modules.  If several images are run in a batch, results from all images may be contained in a single JSON. Since the Arbitrary Charts Module is based on the concept of a custom layout of features, there is no fixed structure to the measurement results that the Module produces. Instead, the module simply produces […]

The Pass/Fail monitor (introduced In Imatest 4.0) provides a real-time indication of whether a device has passed or failed a test. It saves the trouble of digging through results— in figures or CSV or JSON files. Key features: It can stay open while modules run, displaying results immediately after calculations are complete. It works best on systems with a high resolution screen or dual screens. It interfaces with most Imatest analysis modules. It can be extremely valuable for developing and testing Pass/Fail criteria for Imatest IT (Industrial Testing). It can call several utilities for helping with this process. It displays […]

Introduction to Acutance and SQF   Acutance and Subjective Quality Factor (SQF) are measures of perceived print or display sharpness. SQF was used for years in the photographic industry but has remained unfamiliar to most photographers. Acutance is a relatively new measurement from the IEEE Camera Phone Image Quality (CPIQ) group. Both are metrics which incorporate the effects of The imaging system: The Modulation Transfer Function (MTF) of the camera as a measurement of its intrinsic sharpness. The viewer: The human eye’s sensitivity to each spatial frequency modeled with a Contrast Sensitivity Function (CSF). The viewing conditions: The image display height […]

Introduction Part 1 of this page illustrates images analyzed in Random Scale-invariant & Dead Leaves. The images are not shown original size; they’ve been resized to be approximately equal in magnification with respect to the original chart image— with enough magnification to show the results of the camera optics and image processing. Part 2 demonstrates how demosaicing is the cause of a commonly observed discrepancy between Spilled Coins and slanted-edge MTF measurements. Part 1: Images used in Random / Dead Leaves Original pattern (cropped from the middle of the chart), for reference. Original pattern (reduced from file used to print […]

Introduction: Starting in version 4.5, Imatest is capable of performing the cross-correlation based texture blur measurement which is under consideration for ISO 19567-2: Texture Analysis on Stochastic Pattern. This is a texture-blur-analysis method originally proposed in Description of texture loss using the dead leaves target: Current issues and a new intrinsic approach by Kirk et al at Image Engineering.  This method starts from the same principles as the so-called “Direct” method of Cao et al which is the Power Spectral Density-based method described on the Random Module page. The main difference is the Direct method makes use of assumed statistical properties […]

Overview Starting in Imatest 4.4, it is possible to perform basic analysis of a video system’s ability to auto focus (AF), auto white balance (AWB) or auto expose an image (AE). Combined, these three tests may be referred to as AAA analysis. Currently, temporal analysis is only compatible with the following modules: Auto Focus: SFR Auto White Balance: Colorcheck Auto Exposure: Stepchart When you select one of these modules and read a video file, the fourth option in the Imatest Video Reader, plot metric with respect to time, will be made available. Selecting this option begins the appropriate setup for […]

Test Charts creates test chart files for printing on high quality inkjet printers. This page focuses on Scalable Vector Graphics (SVG) charts, many of which are used for measuring sharpness (MTF) with Imatest SFR, SFRplus, eSFR ISO, Checkerboard, and SFRreg. (Bitmap charts are described elsewhere.) SVG charts can be printed any size at a printer’s maximum quality (i.e., resolution) with no limitations, and they generally require much less storage than bitmap images. The SVG charts designed for automated testing with SFRplus and eSFR ISO (based on ISO 12233:2014/2017) have numerous advantages over the familiar but obsolete ISO 12233:2000 chart. Most […]

A comparison of sensitivity to signal processing: Results for additional cameras This page contains additional Slanted-edge, Siemens Star, and Log F-Contrast results for four cameras, in support of claims in Slanted-edge versus Siemens Star that Siemens Star MTF measurements are nearly as sensitive to sharpening as low-contrast (4:1) slanted-edge measurements. The Siemens Star’s high contrast (specified at >50:1) makes it quite sensitive to saturation and to “shoulders” (regions of reduced contrast) in camera tonal response. Slanted-edge MTF measurements are stable, reliable, and more representative of perceived image sharpness under a wide range of conditions (in addition to their many well-known […]

 Analyze the Siemens Star chart New in Imatest 2020.1 (Feb. 2020)  Shannon information capacity can be calculated from images of the Siemens star, with much better accuracy than slanted-edges. The old slanted-edge method has been deprecated.   The white paper, “Camera information capacity: a key performance indicator for Machine Vision and Artificial Intelligence systems“, which briefly introduces information theory, describes the camera information capacity measurement, then shows results (including the effects of artifacts) is now available for download. Imatest 5.0: Half-stars (rotated by multiples of 45º) can now be analyzed. A star-only pattern (without density patches, etc.) can be selected in […]

A comparison of sensitivity to signal processing In this page we address concerns about the sensitivity of slanted-edge patterns to signal processing, especially sharpening, and we correct the misconception that sinusoidal patterns, such as the Siemens star, are insensitive to sharpening, and hence provide more robust and stable MTF measurements. The Siemens Star is of particular interest because, along with the slanted-edge, it is included in the ISO 12233:2014 standard.  To summarize our results, we found that sinusoidal patterns are sensitive to sharpening, though often less so than low contrast (4:1) slanted-edges. The relatively high contrast of the Siemens Star […]

Analysis of random scale-invariant patterns, including the Spilled Coins (Dead Leaves) Pattern, for measuring texture sharpness Introduction – Obtaining – Photographing – Running – Automatic ROI detection – Output  MTF – MTFnn, MTFnnP – Power Spectral Density – Equations & Scale-invariance   Introduction  Random/Dead Leaves, which runs under the interactive Rescharts interface or as a fixed (non-interactive, batch-capable) module, measures SFR (Spatial Frequency Response) or MTF (Modulation Transfer Function) from random scale-invariant (or approximately scale-invariant) test charts, including “Dead Leaves” and “Spilled Coins” charts. It is primarily used to measure the effects of signal processing on image texture. Dead leaves/Spilled Coins charts are of increasing interest because their statistics resemble those of natural […]

Instructions and comments Under development We are updating this page for the latest Skype for Business Video Capture Specification, December 2016. An index of of the Skype/Lync specifications can be found on https://technet.microsoft.com/en-us/office/dn788953 This document contains instructions for using Imatest with the Skype for Business Video Capture Specification, which has two versions: personal solutions (Document Number: H100693) and conferencing devices (Document Number: M1023160), published December 2016. “Skype for Business V3.0” appears on a watermark, and 3.0 is indicated in the Revision History (Section 1). It also contains comments and suggestions for running Imatest. The Skype spec uses only a tiny […]

Instructions and comments We are updating this page for the latest Skype/Lync specification. An index of of the Skype/Lync specifications can be found on  http://technet.microsoft.com/en-us/lync/gg278181.aspx. This document contains instructions for using Imatest with the Skype Hardware Certification Specification — For all Skype Video Devices Version 5.0. It also contains comments and suggestions (some of which we hope might be adopted in a future release of the spec). The Skype spec uses only a tiny fraction of Imatest’s powerful capabilities. To learn more, see Image Quality Factors and SFRplus (which allows many factors to be measured from a single image). In […]

A powerful noise reduction technique called modified apodization is available for slanted-edge measurements (SFR, SFRplus, eSFR ISO, SFRreg, and Checkerboard). This technique can improve measurement consistency for noisy images, especially at high spatial frequencies (f > Nyquist/2), but does not affect the difference in low-noise images. Modified apodization is applied when the MTF noise reduction (modified apodization) checkbox is checked in the settings windows for any of the slanted-edge modules or in the Rescharts More settings window. ISO standard SFR (lower-left of the window) must be deselected. Note: Imatest recommends keeping noise reduction (modified apodization). Apodization comes from Comparison of Fourier transform methods for calculating MTF by Joseph D. […]

On this page: Rise Distance and Frequency Domain | Modulation Transfer Function | Spatial Frequency Units  Summary metrics | MTF measurement Matrix: comparing different charts and measurements | Slanted-Edge measurement | Edge angles | Slanted-Edge modules  Edge contrast and clipping | Slanted-Edge algorithm | Differences with ISO | Noise reduction  Related sharpness techniques | Key takeaways | Additional resources  Measuring Sharpness Sharpness determines the amount of detail an imaging system can reproduce. It is defined by the boundaries between zones of different tones or colors. In Figure 1, sharpness is illustrated with a bar pattern of increasing spatial frequency. The top portion of the figure is […]

Lens aberrations and diffraction are two basic factors that limit lens sharpness. Details regarding these basis factors are provided in the following sections. Lens Aberrations  Imperfections in optical systems arise from a number of causes that include different bending of light at different wavelengths, the inability of spherical surfaces to provide clear images over large fields of view, changes in focus for light rays that don’t pass through the center of the lens, and many more (i.e., coma, stigmatism, spherical aberration, and chromatic aberration). Aberration correction is the primary purpose of sophisticated lens design and manufacturing, and it is what […]

The Edge/MTF plot from Imatest SFR is shown in Figure 1. SFRplus, eSFR ISO, SFRreg, and Checkerboard produce similar results and much more. Figure 1. Edge/SFR results for an SFRplus image from a 10 Megapixel DSLR Upper-Left—A narrow image that illustrates the tones of the averaged edge that is aligned with the average edge profile (spatial domain) plot, immediately below. Middle-Left—Average Edge (Spatial domain): The average edge profile shown here linearized, i.e., proportional to light energy. A key result is the edge rise distance (10-90%), shown in pixels and in the number of rise distances per Picture Height. Other parameters include overshoot and undershoot (if applicable). This plot […]

MTF is a measure of device or system sharpness and is indirectly related to the perceived sharpness when a display or print is viewed. A more refined estimate of perceived sharpness must include assumptions about the display size, viewing distance (typically proportional to the square root of display or print height), and the human visual system (the human eye’s Contrast Sensitivity Function [CSF]). Such a formula, called Subjective Quality Factor (SQF) developed by Kodak scientists in 1972, is included in Imatest. It has been verified and used inside Kodak and Polaroid, but it has remained obscure until now because it was difficult […]