Using PS to compensate for chromatic aberration

What is chromatic aberration

Sometimes, the image of the subject line around the silhouette will appear red or blue color halo (color deviation), this color halo or color deviation is called the phenomenon of chromatic aberration. That part of the image is also like wearing a stereo glasses to see the same effect, it seems that the image generated shaking. There are two kinds of chromatic aberration, which occur in the image edge of the magnification and color difference. Either way, there is a wavelength difference (or color difference) between the three primary colors of the light, which is the result of different refractive indices when they pass through the lens. When the magnification of chromatic aberration, because the wavelength of different image size will also be different, so the closer the edge of the image, the more serious color Halo phenomenon. The magnification chromatic aberration is also called the transverse chromatic aberration, the general wide-angle lens easily produces this chromatic aberration.

On the other hand, position chromatic aberration is caused by the different wavelength of light, which results in the deviation of the focal position of the image, also known as the longitudinal chromatic aberration. A lens with a long focal length, or a telephoto lens, is prone to this chromatic aberration. However, recently, in order to reduce this color offset many manufacturers have adopted the E-D lenses, compared with the previous, chromatic aberration has been largely suppressed.

For position chromatic aberration, tighten aperture after how many can get some inhibition, but including the magnification chromatic aberration, the chromatic aberration itself is determined by its optical characteristic, it is impossible to eliminate it completely when designing the lens. But, like Nikon's camera and Pentax's K-7, the camera's interior is set up to compensate for the chromatic aberration of the image being photographed. And for other models taken photos, can also use post-processing software or Photoshop and other image processing software to compensate for color difference.

Using Photoshop to compensate for chromatic aberration

Using Photoshop to compensate for chromatic aberration

The chromatic aberration generally is more obvious in the contrast high part. This is an example of the magnification difference. It is visible that the lower right part of the building produces a large chromatic aberration. And after using Photoshop to compensate, it is clear clean. Here is a Photoshop compensation example, in fact, most of the image processing software has a red/cyan and blue/yellow compensation function.

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