Introduction – Examples – Oversharpening and Undersharpening – Examples  Unsharp masking (USM) – Links – Standardized sharpening   Introduction to sharpening Sharpening is an important part of digital image processing. It restores some of the sharpness lost in the lens and image sensor. Every digital image benefits from sharpening at some point in its workflow— in the camera, the RAW conversion software, and/or image editor. Sharpening has a bad name with some photographers because it’s overdone in some cameras (mostly low-end compacts and camera phones), resulting in ugly “halo” effects near edges. But it’s entirely beneficial when done properly. Almost every digital camera sharpens images to some degree. Some models […]

Introduction – MTF – MTF equation – Slanted-edge measurements – Why a slanted edge? – MTF measurement matrix  Spatial frequency units – Summary metrics – Results – Noise reduction – Diffraction & Optimum aperture  Interpreting MTF50 – Auto-focus – Calculation details – Imatest vs. ISO calculation – Links Introduction Sharpness is arguably the most important photographic image quality factor because it determines the amount of detail an imaging system can reproduce. Imatest also measures a great many others. Sharpness is defined by the boundaries between zones of different tones or colors. It is illustrated by the bar pattern of increasing spatial frequency, below. The top portion is sharp; its boundaries are crisp steps, not gradual. The bottom portion illustrates how the pattern is degraded after it […]

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 […]

Imatest software can measure a great many digital camera image quality factors from test chart images. If you’re just getting started we recommend that you explore the Image Quality factors page. The two most widely used modules, SFRplus and eSFR ISO, can measure a great many image quality factors from single test chart images. Other modules and charts let you work with a wide variety of testing challenges. Running Imatest – Three helpful buttons – RAW files – Misc. controls and utilities ROI Options – Options II – EXIF data – Dropdown menus – Figures – CSV & JSON output    Running Imatest Imatest […]

Imatest 4.5  The Checkerboard Module, which calculates distortion, MTF, and lateral chromatic aberration is Imatest’s primary recommended means of calculating optical distortion. It produces highly accurate results and works well with highly barrel-distorted (fisheye) images, which cannot be analyzed with the Distortion module. SFRplus also measures distortion with similar results to the Distortion module. A key advantage of SFRplus is that it can measure distortion in highly barrel-distorted (fisheye) lenses using pre-distorted charts. It can also measure Field of View (in addition to performing a great many image quality measurements). Distortion is one of several Imatest modules that calculate optical distortion. These modules […]

           PostProcessor to Spatial Frequency Response (SFR) Slanted Edge Chart:                  Calculates AutoFocus Consistency of a Digital Cameras using a Slanted Edge Image   Standard: ISO/NP 20490  Measuring Auto-Focus Performance of a Digital Camera Technical Committee: ISO/TC 42 Photography Published: 2016-06-02   Introduction to the AutoFocus postprocessor  Imatest 4.5-5.1 can measure Autofocus repeatability of a digital still camera by using Imatest’s SFR module.  This module was deprecated in Imatest 5.2 since the ISO standard for Autofocus was postponed. A method to measure the Autofocus Consistency performance of a digital still […]

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 […]

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 entire site, but […]

Which version is right for you? Imatest 5.0:  All functions of Imatest Image Sensor have been incorporated into Imatest Master.   Imatest is available in several GUI (Graphic User Interface)-based versions. Studio, with everything individual photographers need to test their cameras and lenses. Studio is only available to individual photographers. Master, the full-featured industrial-strength version for engineers and scientists who develop and evaluate imaging systems. Acquire images directly from several manufacturer’s development systems. Images can be updated and analyzed in real time with the Rescharts, Multicharts, and Uniformity-Interactive modules. As of Imatest 5.0, Image Sensor (IS) has been discontinued. All […]

New XML improvements in Imatest 3.5.1+ This page describes changes in the XML output that occurred as of Imatest version 3.5.1. These changes have been made in order to accommodate the Database for test results. Naming Conventions Spacing Words will be separated by underscores. Abbreviations No use of shortened or abbreviated words (such as “corr” for corrected, or “interp” for interpolated). The whole word is now used. Corrected Data No suffix on uncorrected data. For data that is “corrected” there should be a “_Corrected” suffix on the end. XML Schemas for Validation XML schemas have been constructed for validation of […]

Analysis of hyperbolic or trapezoidal wedge patterns with the Imatest Wedge and eSFR ISO modules Introduction Imatest Master and IS can analyze wedge patterns in two modules, both of which may be run from the interactive Rescharts interface or as fixed (batch-capable) modules. The Wedge module (described in this document) can analyze any arrangement of horizontal or vertical (but not diagonal) wedges, using manual region selection. The eSFR ISO module can analyze pairs of wedges on the Enhanced and Extended eSFR ISO charts (including the charts with extra wedges), introduced in April 2014. Region detection is fully automated. The user […]

Introduction Imatest’s slanted-edge algorithms for calculating MTF/SFR are based on ISO 12233 standard, “Photography – Electronic still picture cameras – Resolution measurements”. Although this standard is well-established in industry, we often receive questions regarding its validity. This document describes methods for validating the Imatest slanted-edge method for calculating image sharpness (expressed as Modulation Transfer Function, MTF, which is synonymous in practice with Spatial Frequency Response, SFR). MTF is a measurement of image contrast as a function of spatial frequency. As such, it is a measure of device or system sharpness, which is only indirectly related to perceived image sharpness in […]

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 […]

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. […]

Lens aberrations and diffraction are two basic factors that limit lens sharpness. Details regarding these basis factors are provided in the following sections. Lens (Optical) 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 (or even ashperes) 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 (longitudinal and lateral)). Aberration correction is the primary purpose of sophisticated lens […]

On this page: Rise Distance and Frequency Domain | Modulation Transfer Function | Spatial Frequency Units Slanted-Edge measurement | Slanted-Edge modules | Slanted-Edge algorithm 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 as a bar pattern of increasing spatial frequency. The top portion of the figure is sharp and its boundaries are crisp; the lower portion is blurred and illustrates how the bar pattern is degraded after passing through a lens. Note: All lenses blur images to some […]

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 […]

For more information on how to use INI files in Imatest IT, we recommend the Imatest INI File Reference This document was created by running checkerboard in Imatest 5.2.0. ALPHA on 30-May-2019 22:57:20. For Imatest IT, most of these entries don’t need to be entered. Many don’t affect Imatest IT results: they control interactive figure displays or figure output formats (figures are often not used in Imatest IT). Background Meaning Yellow Yellow background: Important to Imatest IT. Parameter and Description are in boldface. [IT] Cyan Cyan background: Figure settings. (Figures are used infrequently for IT.) [f] Gray Gray background: For […]

For more information on how to use INI files in Imatest IT, we recommend the Imatest INI File Reference For Imatest IT, most of these entries don’t need to be entered. Many don’t affect Imatest IT results: they control interactive figure displays or figure output formats (figures are often not used in Imatest IT). Background Meaning Yellow Yellow background: Important to Imatest IT. Parameter and Description are in boldface. [IT] Cyan Cyan background: Figure settings. (Figures are used infrequently for IT.) [f] Gray Gray background: For interactive operation. No effect on IT. Clear Clear background: Results details (units, scaling, etc.) […]