What are chromatic aberrations and how to fix them?
Perhaps you have heard more than once from photographers that you have critical “chromatic aberration” in your photographs? And the words sound like it’s a disease. Let’s look at what this term means and how to remove aberrations from photographs, if necessary, using advanced technology.
Chromatic aberration is a parasitic dispersion of light passing through an optical system. This may occur due to the lens or incorrect refraction of light when photographing. Chromatic aberration leads to a decrease in the clarity of the image, and sometimes also to the appearance on it of colored contours, stripes, spots, which the subject does not have.
And although modern lenses and cameras are developed using technologies aimed at reducing such glitches, but the fact remains – they still pop up in our pictures. About how to correct chromatic aberration with Photoshop, read below.
Here is an image that can serve as a good example of chromatic aberration. Part of the image is slightly out of focus, due to this there is some loss in detail. Pay attention to the blue halo on the left side of the image and similar colored spots are scattered throughout the area in different areas.
Due to the lens, the passage of light can change, the lens affects the frequency when light passes through the lens, different wavelengths (colors) move at different speeds and are fixed in different places on the sensor. Sometimes, the inappropriateness of using a lens not intended for a specific shooting (for example, macro) can cause chromatic aberration. As a result, red, green and blue do not converge at the desired point and create a display of channels that do not match.
There is, of course, a more technical description of what chromatic aberration is, but for our purposes, such a simple explanation is quite enough to understand how HA affects the image and how to deal with them.
This animation clearly shows how the image is shifted. Each channel can be quite sharp, but when combined, the image quality deteriorates. It is possible that it will be possible to fix images using post-processing programs. For example, Photoshop.
HA elimination in an advanced way
Open the image with HA. This method is based on correcting aberrations by adjusting and aligning the channels so that they correspond to each other. This can be a problem, since light tends to accelerate at various points in the lens, creating more distortion in some areas, but we will try to deal with it.
Start your work by making a copy of the image. We will make most of our adjustments on this layer, but we will also need the original background image when we are done.
Let’s start by setting the green channel to match the red channel. The frequency of light speeds up when the light moves from red to green and blue, so we will adjust the green and blue channels to combine with the slower red frequency. So. Select the green channel. Make sure that the blue channel is turned off so that you can see how the green and red channels overlap.
When the green channel is selected, press Ctrl + A to select everything, and then press Ctrl + T to make a free transformation.
It is necessary to carefully transform the channel so that it matches the outer edges. When done, press Enter and then Ctrl + D to get rid of the selection. Do not worry if some aberration remains on the part of the image. We will fix this later.
The same goes for adjusting blue. Turn the green channel off, then select and turn on the blue as shown.
Carry out a similar adjustment of the blue channel: select everything with Ctrl + A, and then transform the channel with Ctrl + T. When you are done, and your picture will clearly crop off the outer edges, press Enter to complete the transformation.
When you return to the RGB combo channels, you will see that significant aberrations in the photo are eliminated. Such a “repair” is not perfect, part of the image will be somewhat blurred as a result of your actions, so you need to continue to work and eliminate the remaining flaws.
Channel Blur Repair
You can eliminate the blur resulting from the fight against aberrations in different ways, but we offer the most optimal way, in our opinion, that will help to eliminate the blur.
Select the green channel, select all the points of the image in it with Ctrl + A before you move the whole image to the area of sharpness. Repeat the same with the blue channel, watching only the semantic center of the image.
Create an image mask. Use a brush to blend the mask and image together. When you are done, you will have a layer consisting of two sublayers, create a new mask for the group. With it, you can return any of the areas you are interested in to return.