Chromatic aberration is a type of image distortion that occurs due to imperfect optics. This phenomenon is due to the dispersion of light when it passes through the lens of the lens. It is due to the fact that rays having different wavelengths (different colors) have different refractive indices. The white ray is decomposed into the spectrum of all the colors of the rainbow, and the colors are refracted at different angles and focused on different planes.
Chromatic aberration often leads to the appearance of colored contours, spots and stripes, which reduce the clarity of the image and are especially noticeable at the transition of contrasting objects. A good example is a picture of a tree or a building against a sunny sky. This defect is most pronounced with an open diaphragm.
Modern lenses (namely, lenses give chromatic aberration) use low-dispersion elements that give less refraction and a clearer picture. At Nikon, such lenses are indicated by the mark ED (Extra-Low Dispersion). Aspherical lenses are used for the same purpose , allowing you to get an image with fewer such defects. There are also cameras with automatic aberration control.
But if the existing lens still gives these distortions, there are many ways to deal with them. You can use filters, edit photos in one of the editors, or use a plug-in that suppresses chromatic aberration. How to remove these artifacts using Adobe Fhotoshop quickly and easily? One of the options is given below.
Open the RAW file in Photoshop, it is picked up by Adobe Camera Raw. Next, go to the Lens Corrections tab. In the Defringe parameter, specify All Edges, after which the edges become less bright. Now we begin to move the sliders - first Red / Cyan until the blue border fades, then Blue / Yellow until the color areoles disappear. Everything, the picture is ready.
JPEG photos can be edited using a filter such as Distort - Lens Correction. It’s easy to get rid of chromatic aberration using Adobe Lightroom. The advantage of the latter is that after processing one shot, you can use the same settings for the entire series using the Sync function.
The easiest, but not always correct way to remove these annoying artifacts is to convert the image to black and white or initially to shoot in black and white. In addition, knowing that the lens suffers from such a drawback, you need to avoid taking pictures with an open aperture.
Most often, chromatic aberration occurs in lenses with a large zoom ratio. The thing is that at different focal lengths these distortions manifest themselves in different ways, and therefore it is extremely difficult to calculate and compensate for all possible defects in such a complex scheme. That is why lenses with a fixed focal length give a better picture and are, as a rule, much more expensive than “zooms”.
There are other aberrations of optical systems. When using spherical lenses, spherical aberrations occur due to the difference in the distribution of illumination in the middle of the lens and along the edges. This defect is expressed in blurring, resembling a halo. Such aberrations as coma and astigmatism also lead to image blurring. Another common defect, especially typical for wide-angle and telephoto lenses, is optical distortion, which greatly exaggerates the feeling of the depth of the frame. It is expressed in the curvature of straight lines and can be convex and concave.
Most aberrations are currently easy to fix in graphic editors. But sometimes, knowing the features of their technique, it is easier to take them into account when shooting and, if possible, to avoid unsuccessful camera angles.