To compensate for the dispersion, optical systems consist of multiple convex and concave lenses and are made from different glass types with varying dispersion levels.
Lenses that correct dispersion for two wavelengths are called achromatic lenses. Lenses with three corrected wavelengths are called apochromatic lenses.
There are mainly two different chromatic aberration types, longitudinal axial and lateral transverse. Longitudinal chromatic aberration occurs when different wavelengths disperse from the lens at various points along the horizontal optical axis image 3.
Wavelengths scattered across the axis are known as the circle of confusion, leading to unintentional color fringes even in the center of the image. One of the main strategies for reducing longitudinal chromatic aberration is stopping down the aperture as the aperture is responsible for the incoming light quantity. Lateral chromatic aberration occurs when different wavelengths enter the lens at an angle and then focus at various positions along the same focal plane.
Compared to longitudinal chromatic aberration, lateral only develops towards the corners and gets visible at high contrast image structures. It cannot be fixed by stopping down the aperture. Lateral chromatic aberration can only be amended in post-processing software. Even though chromatic aberration is difficult to correct and often impossible to eliminate entirely, many lens solutions can lead to higher quality corrections. An achromatic correction applies to wavelengths at both ends of the visible spectrum red and blue.
An achromatic lens contains, for example, an element of convex crown glass lower on the refraction index and an element of concave flint glass higher on the refraction index. In complex optical systems, these elements are often combined with extra-low dispersion glass ED glass. Apochromatic correction is designed to bring three wavelengths ordinarily red, green, and blue into focus on the same plane.
Three types of glass elements, such as flint, crown, quartz, etc. You see, some wavelengths of light bend more than others when they pass through the lens. And this causes certain colors especially purple, red, green, and blue to appear in unwanted places. Chromatic aberration is a problem caused by your lenses, and basically every lens displays chromatic aberration to some extent.
Because there are methods of minimizing it while shooting—and, if it becomes a serious problem, you can remove it easily in programs such as Lightroom or Photoshop. The first way to minimize chromatic aberration is to buy high-quality lenses. The better the glass, the less chromatic aberration will be an issue. This is because the best lenses Canon mm for example are made to limit the separation of light when it passes through the glass elements.
Look for lenses with low-dispersion elements. These are designed to significantly reduce color fringing. What then? Using small apertures can also mean that you'll need to slow your shutter speed or raise the ISO , but it will help you reduce chromatic aberration in the long run.
So we've talked about how you can minimise longitudinal chromatic aberration by closing down the aperture of your lens. What about the transverse chromatic aberration? What about if you want to place your subject in the bottom or top thirds of the frame, or close to the edges? Well, you can place it in the centre while you are shooting and then crop the image to achieve the composition you were looking for! We've talked about how to avoid chromatic aberrations while shooting on the field, but what about if you weren't able to reduce them for some reason and you still have some annoying colour fringing?
There are two options that will help you to remove chromatic aberrations in Lightroom: the first one is to make the software do its magic and go for the automatic correction, while the second one is to work on it by yourself with the manual correction. Automatic chromatic aberration correction in Lightroom.
In order to find the automatic CA correction in Lightroom, make sure you are in the 'Develop' section of the software. Honestly, Lightroom does an excellent job at dealing with chromatic aberrations.
As you can see, the picture clearly shows some fringing. Meanwhile, in the photo below, there is no visible chromatic aberration at all. Magical, right? No chromatic aberration. Switch to manual mode. Again, start in the 'Develop' section of Lightroom. You should have the same settings as in the photo above.
You can select the affected areas and Lightroom will try to remove the CA from those specific areas by changing some of the parameters. As you can see in the photo below, I played a bit with the Defringe Green slider and the Green Hue, to find the right point where all the chromatic aberration is removed.
I always recommend that you try auto-correction first, as it can be a real time-saver! Removing chromatic aberration manually. Next, open it in full screen mode and at max brightness on your PC. You can also print it and take a few shots with the lens you want to test.
Removing chromatic aberrations can make a photo much more aesthetically pleasing. It bends light, and much like the triangle-shaped prism made famous by Pink Floyd, colors passing through the lens are split at different angles. It may sound simple, but various wavelengths and thus various colors strike your lens all at once, and each of these wavelengths will behave slightly differently depending on the lens glass that it is passing through.
Unfortunately, this is also where chromatic aberration tends to rear its ugly head. Hidden within the design of these lens elements are defects — either in the glass or the design of the lens itself — which, under specific conditions, may cause your photos to exhibit CA. In fact, a key point is that all lenses suffer from chromatic aberration in one form or another, no matter the cost.
What matters is whether or not your lens exhibits visible chromatic aberration, and whether the amount of visible CA is a dealbreaker for your particular needs. Chromatic aberration is a major problem, especially on cheap lenses.
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