Camera MTF (sharpness) measurements are subject to a number of variations, some of which, like noise, are random and difficult to control, and some of which are systematic and can be corrected. Variations caused by limitations in chart sharpness are in the latter category. These variations are also affected by the Field of View (FoV) of the image used to test the camera, which is closely related to chart size for charts designed to fill the camera frame. For a given print technology, increasing the FoV, which typically means increasing the spacing between the chart and camera, will increase the […]

Slanted-edge regions can often have non-uniformity across them. This could be caused by uneven illumination, lens falloff, and photoresponse nonuniformity (PRNU) of the sensor.  Uncorrected nonuniformity in a slanted-edge region of interest can lead to an irregularity in MTF at low spatial frequencies. This disrupts the low-frequency reference which used to normalize the MTF curve. If the direction of the nonuniformity goes against the slanted edge transition from light to dark, MTF increases. If the nonuniformity goes in the same direction as the transition from light to dark, MTF decreases.  To demonstrate this effect, we start with a simulated uniform slanted […]

The obsolete ISO 12233:2000 standard defines a resolution test target with a high contrast ratio. These are typically produced at the maximum dynamic range of a printer, which can be anywhere from 40:1 to 80:1.  The high contrast can lead to clipping of the signal which leads to overstated invalid MTF values.

This paper was given as part of the Electronic Imaging 2017 Autonomous Vehicles and Machine session. When: Monday, January 30, 2017, at 10:10 am By: Norman Koren with support from Henry Koren, Robert Sumner

A fuller and more up-to-date explanation of gamma, including how to obtain it for slanted-edge MTF calculations can be found on Gamma, Tonal Response Curve, and related concepts. Gamma (the average slope of log pixel levels as a function of log exposure for light through dark gray tones) is used, per the ISO 12233 standard, to linearize the input data, i.e., to remove the gamma encoding applied by the camera or RAW converter. Gamma defaults to 0.5 = 1/2, which is typical of digital cameras, but may be affected by camera or RAW converter settings.  Imatest Settings For accurate calculation of edge-SFR from using […]

Infrared Targets  Standard Imatest inkjet-printed test charts produced prior to February 2016 work in Near InfraRed (NIR) wavelengths out to approximately 1 micron. In February 2016 we upgraded our printers and found (to our disappointment) that our new printers do not have the same reflective densities for NIR wavelengths as for visible wavelengths. We are working out solutions to this issue. Please contact us if your needs include NIR.

Measuring MTF is not a typical application for Stepchart— certainly not its primary function— but it can be useful with multiburst patterns, which are a legacy from analog imaging that occasionally appear in the digital world. The multiburst pattern is not one of Imatest’s preferred methods for measuring MTF: see the MTF Measurement Matrix for a concise list. But sometimes customers need to analyze them. This feature is available starting with Imatest 4.1.3 (March 2015).

A correction factor for the slanted-edge MTF (Edge SFR; E-SFR) calculations in SFR, SFRplus, eSFR ISO, SFRreg, and Checkerboard was added to Imatest in 2015. This correction factor is included in the ISO 12233:2014 and 2017 standards, but is not in the older ISO 12233:2000 standard. Because it corrects for an MTF loss caused by the numerical calculation of the Line Spread Function (LSF) from the Edge Spread Function (ESF), we call it the LSF correction factor.

by Jackson K.M. Roland Abstract The slanted-edge method of measuring the spatial frequency response (SFR) as an approximation of the modulation transfer function (MTF) has become a well known and widely

Description: A new set of metrics based on information theory promises to be superior to traditional MTF (SFR or sharpness) and noise for predicting machine vision system performance. We will introduce the new information metrics, which include Noise Equivalent Quanta (NEQ), camera information capacity, Ideal Observer SNR (SNRi – for the quality of object detection), and Edge location standard deviation (Edge σ – for the quality of edge location). We will cover the background of the new measurements, why they are more directly related to object and edge detection than traditional measurements, how to conveniently obtain them (primarily from standard slanted […]

This is a calibrated reference camera for Camera Monitor System (CMS) resolution (MTF) testing, designed to work with Leader SFR-Fit MTF Measurement Software (sold separately).

By using SFR-Fit Ver2.4 and a calibrated reference camera, you can measure the MTF of a CMS electronic mirror.

Includes:

• Calibrated Reference Camera
• Two types of measurement-specific hoods
• Calibration data
• Fixture for estimating the distance between display and cover glass

Imatest attended AutoSens Europe on October 8-10, 2024 in Barcelona, Spain. We presented our advanced testing methods and algorithms for validating the quality of automotive cameras.   Watch On Demand AutoSens Europe Website Virtually Visit Imatest’s Booth Related Products Calibrated Reference Camera for Camera Monitor System (CMS) testing with Leader SFR-Fit Leader SFR-Fit MTF Measurement Software Imatest Spectral Illuminance Color Sensor SFRreg Field Ruggedized Target ISO 12233 Edge SFR (eSFR) Inkjet chart Event Photos Tutorial by Norman Koren Information Metrics for Performance and Optimization of Machine Vision Systems. We discuss the mathematical background and practical measurement techniques for a new set of […]

Analysis of wedge patterns with the  Imatest Wedge and eSFR ISO modules News  2021.2 —  Logarithmic wedges: a superior design describes the advantages of logarithmic wedges, which have a much better distribution of spatial frequencies than hyperbolic wedges, allowing a larger maximum/minimum frequency ratio. Supported by Imatest (automatically detected) since 2021, but (as of May 2022) not currently included in standard eSFR ISO charts (though available on request).  2020.2 —  Calculations were greatly sped up in order to improve performance of direct image acquisition. During the testing of the speedup with direct acquisition, we found that Wedge results were unstable during […]

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 […]

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 […]