It might be just spherical aberration of the lens. In the old film days we would have stop down a fast lens a couple of f stops to reduce the effect.
The first pic is a 50mm f 1.7 shot and the second is the same lens stopped down to f 2.8, not as bright but much sharper.
Last edited by doppler; 06-09-2014 at 08:33 PM.
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