Most of my experiments with a DSLR were with camera lenses on an old Canon 300d – so widefield mainly using fixed focus lenses – 8mm, 50mm and 85mm.
I found images were always better with dark frame subtraction.
I was never really sure how to do flat fields for ‘wide-field’ lenses – so never did.
I did use processing techniques for ‘synthetic’ flats, though, using IRIS.
I have a new camera, Canon 600d, now, but not done much with it so far.
I expect it has much lower noise that the 300d, but whether it is neglible in exposures from 5s to 10s I have yet to measure.
Callum.