Chromatic aberrations in photography

Chromatic aberrations are a kind of image distortion that arise in connection with the imperfection of optics. This phenomenon is due to the dispersion of light as it passes through the objective lens. It is due to the fact that rays having different wavelengths (different colors) have different refractive index. The white ray is decomposed into the spectrum of all the colors of the rainbow, and the colors are refracted at different angles and are focused on different planes.

Chromatic aberrations often lead to the appearance of colored contours, spots and bands, 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 the background of the sunny sky. This defect is most pronounced when the diaphragm is open.

In modern lenses (namely, lenses give chromatic aberrations), low-dispersion elements are used that give less refraction and a clearer picture. Nikon has such lenses as the ED (Extra-Low Dispersion) mark. For the same purpose, aspherical lenses are used , which make it possible to obtain 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 apply light filters, edit photos in one of the editors or use a plug-in that suppresses chromatic aberrations. How to remove these artifacts with the Adobe Fhotoshop program quickly and easily? One of the options is given below.

Open 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, and then the edges become less bright. Now start moving the sliders - first Red / Cyan until the blue fringe fades, then Blue / Yellow until the color areolas disappear. Everything, the picture is ready.

Photos in JPEG format can be edited using a filter such as Distort - Lens Correction. It's easy to get rid of chromatic aberrations and using Adobe Lightroom. The advantage of the latter is that by processing one shot, you can use the same settings for the entire series using the Synchronization function.

The simplest, but not always correct, way to remove these annoying artifacts is to convert the image into a black and white format or initially to shoot in black and white. In addition, knowing that the lens suffers from this disadvantage, you need to avoid taking pictures at the open aperture.

Most often chromatic aberrations occur in lenses that have a large multiplicity of zoom. The thing is that at different focal distances these distortions manifest themselves in different ways, so that 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 "zoom".

There are other aberrations of optical systems. When spherical lenses are used, spherical aberrations arise due to the difference in the distribution of illumination in the middle of the lens and at the edges. This defect is expressed in a lubrication resembling a halo. To blur the image lead and such aberrations as coma and astigmatism. Another common defect, especially characteristic of wide-angle and telephoto lenses, is optical distortion, which greatly exaggerates the sense of depth of the frame. It is expressed in the curvature of straight lines and can be convex and concave.

Most aberrations are now easy to fix in graphic editors. But sometimes, knowing the features of their technique, it's easier to take them into account when shooting and, if possible, avoid unsuccessful camera angles.