Image Quality Factors – Imatest

Validation Methods for Geometric Camera Calibration

Henry Koren — Mon, 23 Mar 2020 06:00:00 +0000

Paul Romanczyk, Senior Imaging Scientist at Imatest, presents his Electronic Imaging 2020 paper. Camera-based advanced driver-assistance systems (ADAS) need the mapping from image coordinates to world coordinates, which geometric calibration provides. The talk describes tests for judging how good a calibration is and for comparing calibration models for an as-built camera, driven by automotive use cases:

Image coordinate system test: are different teams using the same image coordinates?
Reprojection test: forward-project targets through the model onto the image plane
Projection test: inverse-project points through the model out into the world
Triangulation test: how well a multi-camera system locates a point in 3D

Download the paper and slides in Validation Methods for Geometric Camera Calibration. Also on YouTube.

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The Impact of Flare Light on Dynamic Range

Henry Koren — Mon, 29 Jan 2018 07:00:00 +0000

Norman Koren’s talk at the Electronic Imaging 2018 Image Quality and System Performance (IQSP) conference, January 29, 2018.

HDR image sensors can reach a dynamic range of 120 dB or more, but real cameras rarely come close, because flare light (veiling glare) from reflections inside the lens fogs the dark parts of the image. The talk shows how flare depends on the test chart itself, so different grayscale charts give different dynamic range results, and how glare spread and tone mapping can make those results misleading. It proposes a new definition, dynamic range as the range of illumination where low-contrast detail is still visible, and a contrast resolution chart that measures it directly, even on tone-mapped images. That matters most where people and obstacles in shadows must be seen, as in automotive and security cameras.

Read the paper’s abstract and more in Measuring the impact of flare light on dynamic range.

Dynamic range and dynamic range test charts
Contrast resolution measurement and the contrast resolution test chart
The ISO 18844 veiling glare standard and ISO 18844 test chart

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Image Quality Video Series: Distortion

Tue, 27 Jun 2017 00:00:00 +0000

Lens (optical) distortion is an aberration that causes straight lines to curve near the edges of images. It can be troublesome for architectural photography and photogrammetry (measurements derived from images).

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Image Quality Video Series: ISO Sensitivity & Exposure Accuracy

Fri, 09 Jun 2017 00:00:00 +0000

ISO Sensitivity (or ISO speed) is a measure of how strongly an image sensor and/or camera responds to light. The higher the sensitivity, the less light (smaller aperture and/or shorter exposure time) required to capture a good quality image.

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Image Quality Video Series: Uniformity

Fri, 09 Jun 2017 00:00:00 +0000

Lens shading, Light falloff & Vignetting: Where your image becomes darker the further you get from the center. This is due to the radial nature of the lens which collects more light in the center. It can be particularly strong with wide angle lenses. Non-uniformity is also caused by the chief ray angle of light incident to the sensor which has reduced quantum efficiency as the angle increases.

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Image Quality Video Series: Dynamic Range

Tue, 16 May 2017 00:00:00 +0000

The highest quality images are produced by optimizing many key factors. Dynamic Range is characterized by the ratio between the highest light intensity that a camera system can capture and the darkest tones that become indistinguishable from noise. Dynamic range measurements are useful for optimizing system performance and for verifying camera design specifications. Informed consumers seek camera systems with superior dynamic range, which can capture information in dark shadows while maintaining detail in brighter areas.

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Image Quality Video Series: Color Accuracy

Mon, 17 Apr 2017 00:00:00 +0000

Learn the basics of testing color accuracy, including how to process RAW images, measurement techniques, and how to encode color for human perception.

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Image Quality Video Series: Chromatic Aberration

Tue, 21 Feb 2017 00:00:00 +0000

Lateral chromatic aberration (LCA), AKA lateral chromatic displacement (LCD) and “color fringing”, is a lens aberration that causes colors to focus at different distances from the image center. It is most visible near the corners of images. In this video, we will explain the techniques used to measure for LCA.

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Image Quality Video Series: Noise

Mon, 16 Jan 2017 00:00:00 +0000

The highest quality images are created by optimizing many key image quality factors. Noise is an undesirable random spatial variation, visible as grain in film, or pixel level fluctuation in digital images. Learn how Noise effects your camera system using Imatest.

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Image Quality Video Series: Sharpness

Mon, 07 Nov 2016 00:00:00 +0000

The highest quality images are created by optimizing many key image quality factors. Sharpness determines the amount of detail an imaging system can reproduce. Learn how to optimize sharpness in your camera system using Imatest.

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