Several times, I talked about the limitation to photo image quality by light diffraction but I failed to go into the details. To the general request of one reader who asked, I will try to give some explanations to better understand why the digital photographer must absolutely take that into account to make better pictures and to choose its camera.

The first thing to know is that light diffraction is a very general phenomenon and quite natural. It’s been a long time already that scientists and engineers noticed that -on the one hand- light rays are slightly deflected while running through a very small orifice and -on the other hand- two light rays can interact with each other on the condition that they are have very paths nearly perfectly parallel. This is even one of the most significant and founding elements of quantum physics. When you combine both those phenomenons, you will notice that light going through a very small opening like camera lens diaphragm will produce not exactly the expected neat circle but a more irregular and circular shape that you can see in the illustrative figure that goes along this paragraph: Usually named an Airy disk or Airy disc.

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With all this talk about existing Full-Frame photo cameras (Canon EOS 5D, Nikon D3) and about possibly upcoming new ones (Sony Alpha 900, Canon EOS 5D Mk II or some other similar name, etc.) many photographers happy with their existing digital equipment are wondering: “What’s all the fuss about?”

And it’s a good question to ask, but the answer goes with some of the comments about sensor resolution. About the same people who noticed that resolution is not all that counts (despite what is said or implied by some of the major brands on this market) also understand that going Full Frame is a possibly very important decision for the attentive digital photographer.

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