Color contamination

In an image, the result of one color being affected by the presence of another color in close proximity.

In an image, color contamination describes the result of one color being affected by the presence of another color in close proximity.

In some circumstances, it is possible to correct some of the effects of chromatic aberration in digital post-processing. However, in real-world circumstances, chromatic aberration results in permanent loss of some image detail. Detailed knowledge of the optical system used to produce the image can allow for some useful correction. In an ideal situation, post-processing to remove or correct lateral chromatic aberration would involve scaling the fringed color channels, or subtracting some of the scaled versions of the fringed channels, so that all channels spatially overlap each other correctly in the final image.

As chromatic aberration is complex (due to its relationship to focal length, etc.) some camera manufacturers employ lens-specific chromatic aberration appearance minimization techniques. Almost every major camera manufacturer enables some form of chromatic aberration correction, both in-camera and via their proprietary software. Third-party software tools such as PTLens are also capable of performing complex chromatic aberration appearance minimization with their large database of cameras and lens.

In reality, even theoretically perfect post-processing based chromatic aberration reduction-removal-correction systems do not increase image detail as a lens that is optically well corrected for chromatic aberration would for the following reasons:

  • Rescaling is only applicable to lateral chromatic aberration but there is also longitudinal chromatic aberration
  • Rescaling individual color channels result in a loss of resolution from the original image
  • Most camera sensors only capture a few and discrete (e.g., RGB) color channels but chromatic aberration is not discrete and occurs across the light spectrum
  • The dyes used in the digital camera sensors for capturing color are not very efficient so cross-channel color contamination is unavoidable and causes, for example, the chromatic aberration in the red channel to also be blended into the green channel along with any green chromatic aberration.

The above is closely related to the specific scene that is captured so no amount of programming and knowledge of the capturing equipment (e.g., camera and lens data) can overcome these limitations.

 

image
Color contamination
resources
  • The Problem of Color Contamination in Photography on petapixel.com
  • IR Contamination Filter Test: Hoya ProND vs. Tiffen IRND vs. IR Cut on vimeo.com
  • https://www.lynda.com/Elements-tutorials/Correcting-color-contamination/123500/130044-4.html on lynda.com
  • The Components of a Digital Camera‚Äôs Image Sensor on dummies.com
source
Adapted from content published on wikipedia.org
credit
  • Image by Rawpixel: some rights reserved — from flic.kr
Last modified on October 10, 2020, 6:47 pm
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