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Chromatic Aberration and Lens Fringing
Photography: What is Lens fringing or Chromatic Aberrations?
Lens fringing also known as chromatic aberration is an image defect that is caused by the inability of a lens to focus all wavelengths into a single point. White light is made up of the combination of different colors of light. The rainbow colors: red, orange, yellow, green, blue, indigo and violet all make up white light. The apparent differences between the angle of refraction of the wavelengths of light cause a shift wherein some colors are not refracted into the right point. This causes what is known as purple fringing and yellow fringing.
This form of image defect is most common in wide angle cameras. It is because wide angle cameras had to bend light in a greater extent thus, increasing the effect of chromatic aberration. It is also most apparent in the edges of an image. Chromatic aberration is clearly seen when there is high contrast in the image – that means that very dark and very light areas shift suddenly. High quality lenses found in DSLR address this problem with its many combination of high quality lenses.
Fortunately today we have technology that can remove this problem digitally – during post processing. Programs like Adobe Photoshop and GIMP can remove these chromatic aberrations by selectively desaturating the color channel in which these defects occur. This method does not make the image perfect but it improves it considerably.