Originally posted by Na Horuk I also agree that CA can really ruin photos and I try to only use primes with minimal CA.
That is another fallacy - that primes
automatically have less CA than zoom lenses do - in the 1970's there wasn't anything wrong with that assumption, back then zoom lenses were terrible. However these days there are certain cases where zoom lenses are in fact markedly superior to primes lenses at controlling optical aberrations.
From my comparison of the Sigma 8-16mm f/4.5.-5.6 ASPH Vs the DA15mm f/4 ED ASPH:
100% unsharpened crops from the Pentax K5IIs
Sure it is possible to remove chromatic aberrations, but the sharpness of the lens isn't improved by the correction - because the sensor has already captured all that the lens can resolve.
100% unsharpened crops from the Pentax K5IIs - the crop from the Pentax DA15mm has been sharpened and lens corrections have been applied.The crop from the Sigma 8-16mm lens has been untouched.
In fact I think that resolution from lenses is inhibited to an extent by software lens corrections - because the channels have to be resized and interpolated to correct the optical aberrations in the first place - and that interpolation can affect image quality.
The sigma 8-16mm lens has 15 elements in 11 groups, the Pentax DA15mm f/4 ED ASPH has 8 Elements in 6 groups. The sigma lens has almost double the amount of elements in it, when technically the DA15 should be better corrected due to being a single focal length lens and the use of ED glass and aspheric lenses.