Image Quality Factors

Image Quality Factors are also called Key Performance Indicators (KPIs).


Image Quality Factor Video Series

Nov 7, 2016
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九州天下的网址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.

Jan 16, 2017
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九州天下的网址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.

Feb 21, 2017
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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.

Apr 17, 2017
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learn the basics of testing color accuracy, including how to process raw images, measurement techniques, and how to encode color for human perception.

May 16, 2017
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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.

Jun 9, 2017
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九州天下的网址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.

Jun 9, 2017
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Lens shading, Light falloff & Vignetting:
九州天下的网址 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.

Jun 27, 2017
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九州天下的网址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).


Summary table— Image quality factors and corresponding test charts and modules
Sharpness   Noise   Dynamic range, tone, & contrast   Color accuracy
Lens Distortion   Uniformity   Blemishes   ISO Sensitivity
Lateral Chromatic Aberration   Lens Flare (Veiling Glare)   Color Moiré   Artifacts
Data compression losses   Dmax   Color gamut    Texture Detail


Overview of image quality and Imatest measurements

 Image quality九州天下的网址 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 images of the highest quality. Every image quality factor counts.

This page introduces the key image quality factors and briefly describes how Imatest™ measures them— with links to detailed pages. It is a guide to Imatest organized by image quality factors. Other guides include the Tour (organized by module) and Imatest documentation (the Table of Contents).

To illustrate the quality factors, we use this early morning image of Monument Valley from Hunt’s Mesa, near the Arizona-Utah border. 

九州天下的网址image quality measurements are affected by the

  • LensImatest cannot measure lenses by themselves, but lenses can be effectively compared to one another using a single camera body with consistent image processing settings.
  • SensorImatest can measure the performance of the Lens+sensor from minimally-processed RAW images if they are available. Sharpness, distortion, vignetting, Lateral Chromatic Aberration, noise, and dynamic range are the principal factors that can be measured at this stage. Most of these measurements can be clearly classified as good/bad.
  • Image processing pipeline— typically includes demosaicing, color correction, white balance, application of gamma and tonal response curves, sharpening, and noise reduction. Measured from the image delivered to the user (such as in-camera JPEG images). Additional image quality factors include tonal response (contrast, etc.), color response, and many others. The output of the pipeline may be compared to the minimally-processed lens+sensor measurements.The effect of the pipeline on subjective image quality can be highly scene- and application-dependent, making it difficult to assign “good” or “bad” rankings. Imatest results for these factors need to be interpreted carefully. Examples:
    • Higher contrast images often score higher in visual quality assessment tests, but high contrast can cause clipping (visible as burnt-out highlights) in contrasty (often sunlit) scenes. Tonal response curves with “shoulders” can help. See Stepchart and Multicharts.
    • Most consumers find accurate color to be boring, so camera manufacturers “enhance” colors in a number of ways, such as boosting chroma. See Colorcheck and Multicharts.
    • Most consumers dislike noisy images, but software noise reduction (typically lowpass filtering in areas that lack contrasty features) can remove fine texture, resulting in a cartoon-like “plastic” skin appearance. See Log F-Contrast and Random/Dead Leaves.


Summary table

this table summarizes the image quality factors and links to pages where they are described in detail. most of the charts are available from .

Quality factor Chart Module Comments
Camera, lens
Blemishes, Sensor defects Plain, uniformly-illuminated surface
(flat field)
Blemish Detect Can be displayed on flat screen monitor with Screen Patterns and opal diffusing glass. Note [1]
Color accuracy Colorcheck, Multicharts, Multitest  
Multicharts, Multitest  
, general mxn grids, and many other charts Multicharts, Multitest Note [1]
Dynamic range (DR),
Tonal response,
Grayscale step charts Stepchart, Multicharts, Multitest Transmission charts such as the Imatest 36-Patch Dynamic Range chart or the recommended for DR. Algorithm
Reflective step charts (also works with transmissive charts) Dynamic Range Postprocessor for Stepchart, Multitest. Calculates DR by combining several analyses at different exposures. Doesn’t require a transmission chart.
Special charts: , , , ISO-14524
, ISO-15739
Stepchart, Multicharts, Multitest Note [1]. Many are available from the .
, , , Step Charts Multicharts, Multitest  
SFRplus, ISO 12233:2014 E-SFR SFRplus, eSFR ISO SFRplus does not measure DR. eSFR ISO measures ISO 15739 DR. Highly automated. Measures several factors. Available from the .
Exposure accuracy Step charts (reflective) Stepchart, Multicharts, Multitest  
Colorcheck, Multicharts, Multitest  
ISO Sensitivity
(closely related to
Exposure Index)
Step charts Stepchart Two ISO sensitivity measurements are displayed when incident light (lux) is entered. Details in ISO Sensitivity and Exposure Index
Various color and step charts Multicharts, Multitest
SFRplus SFRplus
Colorcheck, Multicharts, Multitest
Lateral chromatic aberration Slanted edge, ISO 12233 charts SFR Available from the . Note [2]
SFRplus, ISO 12233:2014 E-SFR, Checkerboard SFRplus, eSFR ISO, SFRreg, Checkerboard Available from the . Note [2]
Dot pattern Dot Pattern Available from the . Note [2]
Lens distortion Square or rectangular grid or checkerboard, Distortion Printable by Test Charts or displayed on LCD flat screen monitor with Screen Patterns.
SFRplus, ISO 12233:2014 E-SFR SFRplus, eSFR ISO, Checkerboard Highly automated. Measures several factors. Results in the Image & Geometry display.
Dot pattern Dot Pattern Available from .
Light falloff, vignetting Plain, uniformly-illuminated surface Uniformity Can be displayed on flat screen monitor with Screen Patterns. Opal diffusing glass recommended.
Noise Step charts Stepchart  
SFRplus SFRplus Measures flat areas near slanted-edges. Best with low (4:1) contrast charts.
eSFR ISO eSFR ISO Measures noise from grayscale surrounding center of chart.
Wide variety of grayscale stepcharts and color charts Multicharts Works with a large variety of grayscale and color charts if patches are large enough. Can measure sensor (raw) noise.
Sharpness (MTF) Slanted-edge, ISO 12233 SFR, Rescharts
ISO 12233:2000 and 2014 charts available from . Edges printable by Test Charts. Algorithm
SFRplus, eSFR ISO, SFRreg, Checkerboard SFRplus, eSFR ISO, SFRreg, Checkerboard Highly automated. Measures several factors. Available from .
Other charts: Star, Spilled Coins, Wedge, etc. Rescharts, Star, Log F-C, Random, Wedge Both interactive and fixed modules. Each responds differently to signal processing.
Texture detail Log F-Contrast, Spilled Coins (Dead Leaves) Log F-Contrast
Random/Dead Leaves
Lens flare (Veiling glare) Reflective Q-13 or Q-14 step chart with “black hole” Stepchart See Veiling Glare. Note [1]
Color moiré Log Frequency Log Frequency, Wedge  
Artifacts Log F-Contrast
Any arbitrary image
Log F-Contrast
Notes [1,2] SSIM measures degradation due to image processing (primarily compression) by comparing two images: reference and processed.
Dmax (deepest black tone) Custom test chart printed from file, scanned on profiled flatbed scanner Print Test extracts these properties from ICC profiles.
Color gamut

Notes: [1] Not available in Imatest Studio. Available in Master, Image Sensor, etc. [2] can be printed from Test charts九州天下的网址, but we recommend purchasing it from the .