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Chromatic Aberration


Digital Photography Tutorial – Chromatic Aberration

Chromatic aberration is a problem that is common to all types of optical lenses, including of course those used in cameras. You've no doubt read about it in camera reviews, and you may have seen example photos showing the effect, which shows up as red and purple fringes around the details at the edges of the frame. But what exactly is chromatic aberration, what causes it, and how can it be avoided?

The photo below was taken using a recent and popular super-zoom camera from a major manufacturer. At this scale it looks fine…

…but if we take a closer look at the edges of the picture we can see the effects of chromatic aberration quite clearly, with red and blue fringes either side of the dark struts.

As anyone who studied O-level physics will know, a ray of light bends as it passes from one medium into another, a process known as refraction. You've probably seen it demonstrated using a pencil in a glass of water. The difference in refractive index between the air, the glass and the water make the pencil appear to be bent, as you can see below.

This process of refraction is the fundamental concept behind the whole science of optics, and is also the root of the problem of chromatic aberration. Read on to find out how it works, and what exactly Pink Floyd has to do with it...

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