jared_kipe said:
No I mean their optical qualities not being so good. Besides how many stops is 1.2 or 1.0 over 1.4?
Very-wide aperture lenses often exhibit more obvious vignetting (edge darkening) because of the optical effect of light rays having to travel further to the focal plane the further away they are from the optical axis. Also, their minimum aperture is usually less wide (typically only stopping down to f16) since smaller apertures often introduce diffraction (seen as a softening and drop in image contrast). That's maybe what you meant about wide-barrel lenses having lower optical qualities.
That said, at 'normal' apertures (from maybe f2.8 to about f11) the quality of wide-barrel lenses is just about as good as from anything else.
f1.2 is half a stop wider than f1.4. f1.0 is a stop wider than f1.4. FYI f-numbers increase/decrease by a factor of the square-root of 2 (with a little rounding-up to keep things sane).
I used to have a Leica M4-P with a Noctilux 50mm f1.0. It weighed an absolute ton and focussing at f1.0 was like Russian roulette (lens theory tells you that at f1.0 a subject 6ft away gives you depth-of-field of a little over an inch!). Vignetting at full-bore dropped the image edges down by (at a guess) a couple of stops. However, stop down to f5.6/f6.7 and the image was awesome. That lens was a beauty.
(time to take off the rose-tinted specs....
)
