Imaging Tech

Articles on the state of image quality measurement science

Measuring the impact of flare light on dynamic range

Abstract

The dynamic range of recent HDR image sensors, defined as the range of exposure between saturation and 0 dB SNR, can be extremely high: 120 dB or more. But the dynamic range of real imaging systems is limited by veiling glare (flare light), arising from reflections inside the lens, and hence rarely approaches this level. (more…)

Read More

Imatest IS Discontinued with Image Acquisition now Available in Imatest Master

As of Imatest 5.0, Imatest Master now features image acquisition capabilities. Previously, image acquisition capabilities were supported by Imatest IS, which has been discontinued as a separate product. This provides all of our customers with access to the acquisition library. The library supports direct acquisition from a wide range of frame grabbers and cameras, as well as industry standard interfaces. Direct image acquisition cuts out several steps in the image quality testing process and allows for in-the-loop testing with Imatest.

(more…)

Read More

Shooting the Great American Total Solar Eclipse

As predicted by astronomers years in advance, a peculiar cosmic event will occur on the morning of August 21st. Passing directly in front of the sun, the moon will cast a shadow racing across North America at supersonic speeds. From Salem, Oregon to Charleston, South Carolina, the 70 mile wide shadow will darken everything in its path. Outside the path of totality, all of North America will still be able to observe a partial solar eclipse! (more…)

Read More

Challenges in Automotive Image Quality Testing

Imatest’s Norman Koren presents his vision for challenges in automotive image quality testing including resolving low-contrast scenarios.

Read More

Closing the Loop: Distortion Correction

Imatest’s charts and software allow you to measure the characteristics and parameters of imaging systems. Quite often these measurements simply indicate the limits of system performance and expected image quality.

But some Imatest results let you improve image quality— and subsequent images taken by the same system— by correcting measured aberrations. (more…)

Read More

The Effects of misregistration on the dead leaves cross-correlation texture blur analysis

This paper was given as part of the Electronic Imaging 2017 Image Quality and System Performance XIV and Digital Photography and Mobile Imaging XIII sessions.

When: Tuesday, January 31, 2017, at 12:10 pm

By: Robert Sumner with support from Ranga Burada, Noah Kram (more…)

Read More

Measuring MTF with wedges: pitfalls and best practices

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 (more…)

Read More

Testing a macro lens using Checkerboard and Micro Multi-slide

Imatest’s Checkerboard module is our new flagship module for automated analysis of sharpness, distortion and chromatic aberration from a checkerboard (AKA chessboard) pattern. The big benefit of using the checkerboard is that there are looser framing requirements than with other kinds of test targets. While checkerboard lacks the color and tone analysis provided by SFRplus and eSFR ISO, these features are not available on the high precision chrome on glass substrate, so the checkerboard is the optimal pattern for this test.

Read More

Using Sharpness to Measure Your Autofocus Consistency

Autofocus plays a major role in many camera system applications with variable focus, including consumer electronic devices. Camera systems must be able to focus at a variety of distances. Optical systems on cameras only allow a certain range of distances from the camera to be in focus at once (this is often known as the depth of field, or depth of focus). (more…)

Read More

Imatest Support for CPIQ Metrics

What is CPIQ?

IEEE-SA working group P1858 created the CPIQ standard. CPIQ seeks to standardize image quality test metrics and methodologies across the mobile device industry, correlate objective test results with human perception, and combine this data into a meaningful consumer rating system.
(more…)

Read More

Color difference ellipses

Starting with Imatest 4.2, Imatest’s two-dimensional color displays— CIELAB a*b*, CIE 1931 xy chromaticity, etc.— in Multicharts, Multitest, Colorcheck, SFRplus, and eSFR ISO can display ellipses that assist in visualizing perceptual color differences. You can select between MacAdam ellipses (of historical interest), or ellipses for ΔCab (familiar but not accurate), ΔC94, and ΔC00 (recommended).

Read More

Measuring Multiburst pattern MTF with Stepchart

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).

(more…)

Read More

LSF correction factor for slanted-edge MTF measurements

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 4.1.2 (March 2015). This correction factor is included in the ISO 12233:2014 standard, 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. (more…)

Read More

A Study of Slanted-Edge MTF Stability and Repeatability

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 (more…)

Read More

Slanted-Edge versus Siemens Star: A comparison of sensitivity to signal processing

This post addresses concerns about the sensitivity of slanted-edge patterns to signal processing, especially sharpening, and corrects the misconception that sinusoidal patterns, such as the Siemens star (included in the ISO 12233:2014 standard), are insensitive to sharpening, and hence provide more robust and stable MTF measurements. (more…)

Read More

Sharpness and Texture Analysis using Log F‑Contrast from Imaging-Resource

Imaging-resource.com publishes images of the Imatest Log F-Contrast* chart in its excellent camera reviews. These images contain valuable information about camera quality— how sharpness and texture response are affected by image processing— but they need to be processed by Imatest to reveal the important information they contain.

*F is an abbreviation for Frequency in Log F-Contrast.

(more…)

Read More

No Perfect Lens, No Perfect Lens Test

Roger Cicala of LensRentals.com has completed the second part of his two part series investigating lens testing. (more…)

Read More

Transmissive Chart Quality Comparison

Imatest currently sells several transmissive (backlit) test charts, which have a range of substrates, each with specific properties and qualities that are in process of being quantified. The following comparison of the most important of our transmissive substrates was prepared in response to several customer inquiries.

(more…)

Read More

Measuring Test Chart Patches with a Spectrophotometer

Using Babelcolor Patch Tool or SpectraShop 4

This post describes how to measure color and grayscale patches on a variety of test charts, including Imatest SFRplus and eSFR ISO charts, the X-Rite Colorchecker, ISO-15729, ISO-14524, ChromaDuMonde CDM-28R, and many more, using a spectrophotometer and one of two software packages.

(more…)

Read More

Measuring the Effects of Tilt

Summary: The physical lens-to-sensor tilt angle is difficult to measure from images, but the effects of tilt on image quality are highly measurable, and can be included in pass-fail criteria.

(more…)

Read More