Stephen, I once considered the Sigma 24mm f/1.8, I think it’s a fantastic low-light prime, especially on a cropped sensor DSLR. You’ll definitely be sacraficing some corner sharpness compared to the Canon, but personally that doesn’t bother me because I always soften the edges of my images anyway…

Hawk Ebay for a week or so for the Sigma 24mm and maybe even the 20mm. Right now on KEH, there’s a 20mm (Canon mount) for $325, and I bet if you hawk KEH and Ebay you could find one for about that much or 10-20% less.

I already bought the Tokina 17mm f/3.5, so I’m not going to invest in any more primes until I start seeing new digital-only primes that actually “equal” the 24mm f/1.4 view on a cropped sensor, like maybe a 16mm f/1.4. THAT would blow me away!

-Matt-

Hey again Stephen,

I think you’d have a substantial advantage with the cropped sensor because you’d be cropping away a lot of corner softness that the Sigma might have. The 5D, at 12 megapixels and “FF”, is BRUTAL on lenses and some lenses just might not do it justice. (The resolution of the camera might surpass the resolving ability of the lens…) I’m not saying the Sigma is necessarily in that category of un-acceptable lenses, in fact the Sigma has a very sharp center, it’s just the edges that get soft. Personally for me that’s okay, but other people may like to put subjects closer to the corner than I like, and would HAVE to get the Canon lens…

The Tokina is one lens on the other hand that I think is an amazing performer even on the 5D. It’s super sharp on a cropped sensor D70, but the corners are STILL sharp on my old FM2 with film, as well. So that’s definitely a great lens to consider for both sensor sizes, if you are looking for the simplicity of a prime. Canon’s widest prime is 20mm as far as I know, and it’s build quality is nowhere near the Tokina’s…

Not interested in the Tokina 16-50 f/2.8 DX that I’ve been posting about on Camera Talk? It is $660 of course, which is definitely a turn-off if you don’t absolutely need the zoom…

I’m not sure what’s going on in the Canon EF-S camp, but Nikon DX is allegedly going to release a handful of new DX lenses soon, presumably super-wides like 16mm DX primes, maybe even fast-apeture DX primes, like a 17mm f/1.4 DX or something… THAT would be sweet, for those who plan on sticking with the cropped sensor size…

-Matt-