• August 20, 2024

    Validating the Imatest slanted-edge calculation

    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.

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  • September 4, 2026

    Chart Quality Index (CQI) (deprecated)

    Imatest 5.1 has important new capabilities for measuring and correcting MTF degradation caused by test charts. These new capabilities are far easier to understand and apply than CQI.

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  • April 17, 2026

    Slanted edge vs. Siemens star MTF calculations

    The goal of this document is to compare the effects of demosaicing and sharpening (or bilateral filtering) on MTF measurements for the two most widely used test patterns — the slanted edge and the sinusoidal Siemens star.

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  • August 13, 2025

    Color/Tone Test Chart Reference & Guide

    This post is a guide to selecting test charts for the Imatest Color/Tone module. It describes general properties for all charts, then specific properties of each chart, including recommended uses, advantages and disadvantages.

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  • April 6, 2025

    Simatest – Camera/ISP Simulator – Overview

    Simatest — Imatest's Camera and ISP (Image Signal Processing) Simulator, introduced in early 2025, simulates complete camera systems, including the effects of lens degradations, image sensor noise, and ISP pipelines, enabling all important image quality factors (KPIs) to be predicted.

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  • March 18, 2025

    Image Sensor Noise – measurement and modeling

    The image sensor noise model is the heart of the Simatest Camera/Image Signal Processing (ISP) simulator. It enables camera performance (SNR, image information metrics, and more) to be characterized and simulated for a wide variety of conditions, especially low illumination levels.

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  • January 15, 2025

    Simatest ISP/Camera simulator examples

    This page contains several examples showing how to use Simatest, Imatest's camera and image signal processing simulator, for modeling and measuring camera system performance.

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  • August 20, 2024

    Diffraction, Optimum Aperture, and Defocus

    Lens aberrations, diffraction, and defocus (or focus error) are basic factors that limit lens sharpness. This article describes each of them.

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  • August 20, 2024

    Sharpening

    Sharpening is an important part of digital image processing. It restores some of the sharpness lost in the lens and image sensor.

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  • November 7, 2012

    Slanted-Edge SFR Saturation

    The following (Rescharts) SFRplus results shows the edge (unnormalized) and MTF results for one region near the center of the image that has the green channel saturated.

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  • December 12, 2023

    MTF curves and Image appearance

    Modulation Transfer Function (MTF) is a fundamental measure of imaging system sharpness. It is introduced in Sharpness and discussed further in Sharpening. MTF is measured by Imatest SFR, SFRplus, and by several Rescharts modules.

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  • December 12, 2023

    Sharpness Comparisons for several digital cameras

    Several websites publish images of ISO 12233 test charts that can be entered into Imatest SFR to obtain detailed sharpness measurements. This page contains sharpness results derived from charts downloaded from two sites, Dpreview.com and Imaging-resource.com.

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  • July 4, 2021

    Gamma, Tonal Response Curve, and related concepts

    In this post we discuss a number of concepts related to tonal response and gamma that are scattered around the Imatest website, making them hard to find. They are assembled here in anticipation of questions about gamma and related concepts, which keep arising.

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  • January 31, 2021

    Three optical centers

    Customers frequently want to know how we measure the optical center of the image (not to be confused with the geometrical center).

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  • December 6, 2018

    Recommended Reading

    Books we recommend for learning more about imaging, from digital image processing and camera image quality benchmarking to camera monitor systems, with a note on who each one suits.

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  • November 8, 2018

    5 Common Pitfalls in Image Quality Testing

    Having trouble with your Imatest test results? This article explains the five most common pitfalls in image quality testing, and how to resolve them.

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  • July 15, 2010

    Slanted Edge Noise reduction (Modified Apodization Technique)

    Imatest's Modified apodization technique reduces noise, making MTF results more consistent, while having a minimal effect on MTF measurements. It works by smoothing the Line Spread Function (LSF; the derivative of the edge) at a distance from the edge center, but not near the center.

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