Overview and introduction to measurements   Summary table— Image quality factors and corresponding test charts and modules Sharpness   Noise   Tonal response & contrast   Color accuracy Lens Distortion   Light Falloff & Nonuniformities   Blemishes   Dynamic range  Lateral Chromatic Aberration   Veiling Glare   Color aliasing and moiré   ISO Sensitivity   Data compression losses   Texture Detail   Print Dmax & color gamut    Software artifacts  Overview and Imatest measurements  Image quality is one of those concepts that’s greater than the sum of its parts. But you can’t ignore the parts if your goal is to produce […]

Spanish language translation: Glosario en Espanol Aliasing Low frequency artifacts, sometimes quite disturbing, that appear when the image sensor receives significant signal energy above the Nyquist frequency. Color aliasing in Bayer sensors can be particularly troublesome. “Moire fringing” is a type of aliasing. See diagram in Nyquist frequency, below. Controlled by means of Anti-Aliasing (Optical Lowpass) Filters, which blur the image slightly (a classic tradeoff).  Aperture   The circular opening at the center of a lens that admits light. Generally specified by the f-stop (f-number), which is the focal length divided by the aperture diameter. A large aperture corresponds to […]

Photographing the chart – Running Stepchart – Settings – Output – Temporal noise Auto-exposure – Saving – Dynamic range (DR) – DR definitions – Algorithm   Stepchart measures the tonal response, noise, dynamic range, and ISO sensitivity of digital cameras and scanners using Reflective grayscale step charts such as the Kodak/Tiffen Q-13 and Q-14 Gray Scales, which have a single row of patches (a linear arrangement), or charts such as the ISO-14524 or ISO-15739 charts, with non-linear (multiple rows; may be circular) patch arrangements, shown below, or Transmissive (backlit) grayscale step charts such as the Imatest 36-patch Dynamic Range or 36-patch […]

Interactive Analysis of Resolution-Related Charts New in Imatest 5.1  Chart MTF compensation has been added to compensate for chart limitations. This can double the maximum megapixel capacity of most charts. Imatest 5.0  Nonuniform lighting perpendicular to the edge can be compensated. This improves the estimate of summary metrics such as MTF50. Imatest 4.3:  The Checkerboard module analyzes tilted checkerboard charts for distortion (with great accuracy), MTF, and Lateral Chromatic Accuracy. Imatest 4.2:  SFRreg automatically detects registration mark patterns: useful for measuring at infinity distance in compact systems and for measuring extreme fisheye systems (>180 degrees). Rescharts.ini (where saved settings are stored) has been merged into […]

Test Charts creates test chart files for printing on high quality inkjet printers. This page focuses on Scalable Vector Graphics (SVG) charts, most of which are used for measuring sharpness (MTF) with Imatest SFR and SFRplus. (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 have numerous advantages over the widely-used (pre-2012) ISO 12233 chart. Most of these charts are available through the Imatest Store. We do not […]

In addition to linear step charts (which have a single row of patches), three Imatest modules— Stepchart, Color/Tone Interactive (formerly Multicharts), and Color/Tone Auto (formerly Multitest)— can analyze the tonal response and noise of a number of additional multi-row grayscale charts (reflective and transmissive), most of which are available from the Imatest Store. With most of these charts you can choose between default reference values and a custom reference file that you can measure, or (for 26-patch Dynamic Range charts) are supplied by Imatest. The recommended charts on this page are the 36-patch Dynamic range, ISO-14524, ISO-15739, and 20-patch circular […]

 Analyze the Siemens Star chart News:  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 new feature will be available in the Pilot program prior to the release. 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 Chart configuration. Stars with no inner circles can be analyzed. Bar (square wave) star patterns can be analyzed with a few restrictions. Stars with 24 or 16 cycles […]

The SFRplus chart: description and how to photograph it Watch on YouTube. Download 1080p/720p/540p. Purchase SFRplus Test Charts from the Imatest Store. Imatest SFRplus performs highly automated measurements of several key image quality factors using a specially-designed test chart that may be purchased from the Imatest store (recommended) or printed on a high-quality inkjet printer. The user does not need to manually select Regions of Interest (ROIs). Image quality factors include Sharpness, expressed as Spatial Frequency Response (SFR), also known as Modulation Transfer Function (MTF), which can be mapped over the entire image, Noise (limited: eSFR ISO has more detailed […]

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 – Using RAW files – Bayer RAW and RCCC files – dcraw demosaicing – DNG files – Rawview utility – Generalized Read Raw – Decompanding – Creating Synthetic raw images   The unprocessed digital output of an image sensor is called RAW image data. In this document, we sometimes refer to RAW files from commercial cameras or development systems as Camera RAW to distinguish them from Bayer RAW files, which are standard monochrome image files that contain undemosaiced (Bayer) data. Bayer Color Filter Array (CFA)  The pixels in most digital image sensors are covered with the Bayer CFA, which makes […]

including raw (image sensor), chroma, and visual noise as well as several types of Dynamic Range calculation News– Imatest 5.2: Multicharts (the highly interactive module for measuring color accuracy, tonal response, and noise) has been renamed to Color/Tone Setup, and Multitest (the fixed/batch-capable version of Multicharts) has been renamed to Color/Tone Auto. For now the old names will be used for INI file sections. An INI File Monitor captures the contents of INI files (which can be used control Imatest IT runs), and displays them in a web browser table.  Imatest 5.1: Color/Tone Setup and Auto can now measure temporal […]

View Release Notes Table of Contents Image quality — Sharpness — Other IQ factors — IQ Utilities —  Getting started — Imatest Instructions – general — Troubleshooting —  Knowledge Base highlights — Sharpness modules — Tone, Color, Noise & Dynamic Range modules — Spatial & Uniformity modules — Miscellaneous modules and utilities — Industrial Testing edition — Appendix Offline (local) documentation  Imatest documentation can now be viewed offline. Download this small (8MB) zip file (only the main documentation pages) to a convenient location, then unzip it. The Imatest site folder will contain a mirror of the Imatest documentation website (not the […]