chromatic aberation?

Discussion in 'Beyond the Basics' started by quad b, Aug 9, 2007.

  1. quad b

    quad b TPF Noob!

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    what is chromatic aberation?
     
  2. Chris of Arabia

    Chris of Arabia Herding cats since 1988... Supporting Member

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  3. Dcb18c5

    Dcb18c5 TPF Noob!

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    In optics, chromatic aberration is caused by a lens having a different refractive index for different wavelengths of light (the dispersion of the lens). The term "purple fringing" is commonly used in photography, although not all purple fringing can be attributed to chromatic aberration.
    Longitudinal and lateral chromatic aberration of a lens is seen as "fringes" of color around the image, because each color in the optical spectrum cannot be focused at a single common point on the optical axis.
    Since the focal length f of a lens is dependent on the refractive index n, different wavelengths of light will be focused on different positions. Chromatic aberration can be both longitudinal, in that different wavelengths are focused at a different distance from the lens; and transverse or lateral, in that different wavelengths are focused at different positions in the focal plane (because the magnification of the lens also varies with wavelength).
    Similar colored fringing around highlights may also be caused by lens flare. Colored fringing around highlights or dark regions may be due to the receptors[clarify] for different colors having differing dynamic range or sensitivity -- therefore preserving detail in one or two color channels, while "blowing out" or failing to register, in the other channel or channels. On digital cameras, the interpolation technique is likely to affect the apparent degree of this problem.
    On photographs taken using a digital camera, very small highlights may frequently appear to have chromatic aberration where in fact the effect is because the highlight image is too small to stimulate all three color pixels, and so is recorded with an incorrect color. This may not occur with all types of digital camera sensor. Again, interpolation technique may affect the apparent degree of the problem.
     
  4. Garbz

    Garbz No longer a newbie, moving up!

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    Now if this isn't just plain advertisement for wikipedia I don't know what is ;)
     
  5. Don Simon

    Don Simon TPF Noob!

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    Chromatic aberration is something we should be kept awake at night worrying about, if we are to believe some lens reviewers. Personally I have never found it to be a major problem - especially in prints as opposed to staring at 100% view in Photoshop - except with the very cheapest lenses.
     
  6. guppyman

    guppyman TPF Noob!

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    Thanks for the pro knowledge.
     
  7. Alex_B

    Alex_B No longer a newbie, moving up!

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    Well you can find me in shops and on the street, just 5 inches away from huge 3x3m print complaining about the chromatic abberration ;) ... well this is just a hobby of mine ;)
     
  8. abraxas

    abraxas No longer a newbie, moving up!

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