In January 2013 Imatest released the Spilled Coins test chart, which is an improved version of the Dead Leaves chart for measuring a camera’s fine texture response. (It’s available in the Imatest Store in both monochrome and color versions.) Shortly afterwards, Jason Cope of our partner company Image Quality Labs found an anomalous result and called me to find out what was wrong. When I looked at the image I realized that he’d done the test correctly. He had found an image whose processing defeated the intent of the dead leaves chart, which is to accurately measure a camera’s texture […]

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 […]

Analysis of random scale-invariant patterns, including the Spilled Coins (Dead Leaves) Pattern, for measuring texture sharpness   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 scenes; they are less affected by edge sharpening than other patterns (especially the […]

 Analyze the Siemens Star chart News  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 can be analyzed. Imatest 4.0:  Automatic region detection is available for a new version of the Star Chart that has registration marks on the sides. See below. A new web page, Slanted-edge versus Siemens Star – A comparison of sensitivity to signal processing, […]

Analysis of Log Frequency-Contrast charts New in Imatest 4.0  Automatic region is available with the revised version of the chart, which includes registration marks in the corners. Sharpness and Texture Analysis using Log F‑Contrast from Imaging-Resource compares the the effects of sharpening and noise reduction in several cameras using images downloaded from Imaging-Resource.com. Introduction Log F-Contrast (short for Log Frequency-Contrast; not in Imatest Studio) measures the effects of signal processing— noise reduction and sharpening— on imaging system performance using a chart that varies in spatial frequency on the horizontal axis (log frequency increases with x) and in modulation (i.e., contrast) […]

Analysis of log frequency-varying charts Introduction Log frequency, which uses the Rescharts interface, measures the contrast of narrow bar or sine charts that increase logarithmically in spatial frequency. It also measures color Moiré (Imatest Master only). When the image pattern is sinusoidal (rather than a bar chart), contrast is equivalent to SFR or MTF. This method is more direct than the slanted-edge method, but less accurate and more susceptible to noise. A chart can be created by Test Charts and printed on a high quality inkjet printer. Log Frequency image (complete and cropped) The image above used to illustrate the […]

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 […]

Imatest Checkerboard performs highly automated measurements of sharpness (expressed as Spatial Frequency Response (SFR), also known as Modulation Transfer Function (MTF), Lateral Chromatic Aberration, and optical distortion from images of checkerboard patterns (with a recommended tilt angle of 2-7 degrees for sharpness measurements). New in Imatest 5.1:  Distortion correction arrows and lines can be displayed. 5.0 (builds after March 2018): Distortion calculations (including decentering) have been greatly improved. 4.5:  Checkerboard, for testing checkerboard patterns, is introduced.   The primary advantages of Checkerboard are: Compared to Imatest’s other automatically-detected sharpness modules:  It is relatively insensitive to framing. You can zoom in […]

Running SFRreg (Interactive and Auto mode settings) Imatest SFRreg performs highly automated measurements of sharpness (expressed as Spatial Frequency Response (SFR), also known as Modulation Transfer Function (MTF)) and Lateral Chromatic Aberration from images that contain registration mark patterns (circles that contain two light and two dark quadrants). This document shows how to run SFRreg in Rescharts and how to save settings for automated runs. Part 1 introduced SFRreg and explained how to obtain and photograph the chart. Part 3 illustrates the results. Open Imatest by double-clicking the Imatest icon on the Desktop, the Windows Start menu, the Imatest folder (typically […]

Imatest SFRreg performs highly automated measurements of sharpness (expressed as Spatial Frequency Response (SFR), also known as Modulation Transfer Function (MTF)) and Lateral Chromatic Aberration from images that contain registration mark patterns (circles with two light and two dark quadrants). Unlike standard test charts, these patterns do not need to be located on a flat (planar) surface. Since Region of Interest (ROI) detection is automatic, they may be positioned where needed. Depending on the image source, they offer several advantages. You can Test images at infinity distance (or any distance of choice) using a compact projection system such as a collimator […]

Imatest eSFR ISO performs highly automated measurements of several key image quality factors using versions of the new ISO 12233:2014 E-SFR (Edge SFR) test chart that may be purchased from the Imatest store (recommended) or printed on a high-quality inkjet printer. Region of Interest (ROI) selection is automatic, based on user-entered criteria (similar to  SFRplus, which it closely resembles). Image quality factors include: Sharpness, expressed as Spatial Frequency Response (SFR), also known as Modulation Transfer Function (MTF) Lateral Chromatic Aberration Distortion (with less detail than the Distortion module). Details in SFRplus Distortion and Field of View measurements. Noise, measured from the […]

SFRplus and eSFR ISO can tolerate moderate amounts of optical distortion (pincushion or barrel), but they have definite limits. In this page we describe special versions of SFRplus and eSFR ISO charts that can work with highly barrel-distorted (“fisheye“) lenses, with fields of view up to around 160 degrees— which are used in a number of applications, particularly for automotive rear-view and sports cameras. Cameras with fields of view over 160 degrees— even approaching 360 degrees— can be tested with the SFRreg module, which uses multiple individual “registration mark” charts facing the camera. Pre-distorted charts should only be used with […]

Imatest Rescharts slanted-edge modules perform highly automated measurements of several key image quality factors using specially-designed test charts. The user never has to manually select Regions of Interest (ROIs). This page covers results that are (mostly) not derived from the slanted-edges themselves, including Noise (best in eSFR ISO) Distortion  (differing detail in different modules; best with SFRplus and eSFR ISO. Described in detail here. Tonal response*  (no noise statistics for SFRplus) Color accuracy*  when used with an SFRplus, eSFR ISO, or SFRreg center charts that contain a color pattern Vanishing resolution, aliasing, and Moiré from Wedge patterns in eSFR ISO ISO sensitivity*  (Saturation-based and […]

Imatest Rescharts slanted-edge modules perform highly automated measurements of several key image quality factors using specially-designed test charts. The user never has to manually select Regions of Interest (ROIs). This page covers results that are derived from the slanted-edges, and hence are found in all Rescharts slanted-edge modules. It also covers text output (CSV and JSON) files. Sharpness, expressed as Spatial Frequency Response (SFR), also known as the Modulation Transfer Function (MTF), Lateral Chromatic Aberration Other results, not derived from slanted-edges are covered in Part 4. Noise (best in eSFR ISO),  Distortion  (differing detail in different modules; best with SFRplus and eSFR […]

Running Rescharts slanted-edge modules (Interactive and Auto mode settings) Imatest Rescharts slanted edge modules— SFRplus, eSFR ISO, SFRreg, and Checkerboard— perform highly automated measurements of several key image quality factors using specially-designed test charts. This document shows how to run these modules in Rescharts and how to save settings for automated runs.  Four introductory pages —  SFRplus, eSFR ISO, SFRreg, and Checkerboard — describe each module and explain how to obtain and photograph the chart.  Rescharts Results Part 3 and Part 4 illustrate the results. Selecting files – Setup window – ROI selection & analysis – Edge ID files – More settings window […]

Imatest SFR allows you to analyze and display several regions of interest (ROIs) in an image. Display options can be selected from three dropdown windows from the SFR settings window. Multi-ROI plots lets you choose the plot type: 1D or 2D; units in Cycles/Pxl, LW/PH (Line Widths per Picture Height), or LP/PH (Line Pairs per Picture Height).The 1D summary plots, which display results as a function of the distance from the image center, may be difficult to read for lenses that are poorly centered and hence have asymmetrical response. In most cases 2D summary plots are far more readable. 1D […]

A pattern on an LCD screen may be used for SFR measurements using a pattern generated by the Imatest Screen Patterns module, which has several patterns to choose from. These patterns are convenient, but somewhat limited in usefulness because an LCD screen can only cover a fraction of the image frame, hence you can’t produce a good map the camera’s MTF response. Screen Patterns The Screen Patterns module is opened by clicking on Screen Patterns on the right of the Imatest main window. When it first comes up, it is completely blank (for use with Light Falloff). Select SFR: Quadrants […]

Imatest is opened by double-clicking the Imatest icon on the Desktop, the Windows Start menu, the Imatest folder (typically C:Program filesImatest in English language installations). After several seconds, the Imatest main window opens. Then click on SFR or Rescharts on the upper left. SFR allows you to analyze multiple regions and to run batches of files. Rescharts (1. Slanted-edge SFR) allows you to analyze single regions in a highly-interactive interface. ISO 12233 chart images, which have contrasty slanted-edges, can be downloaded from dpreview.com reviews, typically in the last page titled “Compared to…,” and from Imaging-resource.com reviews, typically on the page […]

Setting up and photographing SFR test charts Imatest SFR measures spatial frequency response, also known as the Modulation Transfer Function (MTF), of digital cameras using a slanted-edge (light-to-dark) target, as described in Sharpness: What is it and how is it measured? Although it doesn’t provide the as strong a visual indication of MTF as wedge or sinusoidal chats (such as Log Frequency), it provides a more accurate quantitative measurement and uses space much more efficiently. Old ISO 12233:2000 test chart (left) with Imatest SFR cropping indicated by the red rectangle New ISO 12233:2014 test chart (right– supported with a high […]

Testing lenses: Introduction Lens quality (especially sharpness) has always been of great interest to photographers. It’s what we spend the big bucks for— if we have them. And it’s what we look for in a lens at any price point. Traditionally, lens testing has been highly tedious, best left to professionals and large publications. With Imatest, that has changed forever. All you need to do is photograph an SFRplus, ISO-12233:2014+ eSFR, or tilted checkerboard chart (with careful technique of course), run SFRplus or eSFR ISO, and interpret the results. This page contains the recommended procedure for testing lenses using Imatest […]