On a T5i which has a 1.6x crop with the APS-C sensor, the choices for a 'walk-about' everyday prime lens are pretty much as follows:
- Canon 35mm f/2 - Old design, buzzy AF-D motor, only 5 aperture blades give somewhat harsh bokeh
- Canon 35mm f/2 IS - The new version, with image stabilization and seriously good bokeh.
- Sigma 30mm f/1.4 - only fully works on crop dslr bodies, but the colors and rendering from this glass is quite nice for the price
- Canon 28mm f/2.8 IS - New optical formula compared to 28 1.8, has image stabilization, good color rendition, but leaves you feeling kind of "meh" unless you do a lot of video work where IS helps.
- Canon 28mm f/1.8 - The colors are typical midgrade Canon (which is to say, quite nice), fast ring USM AF, small, light, and f/1.8.
- Sigma 35mm f/1.4 - Crazy sharp, solid lens with great performance,
- Canon 24mm f/2.8 IS - Newer optical formula, good if you like normal but slightly wider perspective, has Image stabilization but only f/2.8
- Canon 24mm f/1.4L - As odd as it sounds, this is by far my favorite lens on crop for a walk-around prime lens.
- Canon 35mm f/1.4L - Also a great lens with nice overall rendition, but optically its being eclipsed by the Sigma 35 and is more expensive than the Sigma.
The sigma 30mm is pretty close price wise to the 28 1.8 and the 24/28/35 IS lenses, but getting a copy that focuses properly straight out the box is still unfortunately a bit of a lottery. Sigma does now have a USB dock to calibrate their new Art series lenses though.
I've tried the Canon 35 f/2, 35 f/2 IS, 28mm f/1.8, the Sigma 30mm f/1.4, and rented the Canon 24L. My favorite by far was the 24L, the perspective was nice (~38mm FF field of view), but the more economical choice of the 28 f/1.8 would be my first choice. Why? Ring USM is both accurate and fast, ... bloody fast. Also it gives you a max aperture of f/1.8 which is of course desireable. The field of view is roughly equivalent to ~45mm FF which is again, nice if you had prior experience with film stuff. With my copy it's sharp enough in the center wide open at f/1.8, though you'll find tons of conflicting reports about this lens due to both operator error and excessive pixel peeping. Also the minimum focusing distance on the 28 1.8 is ~9.8 inches (but so are the 24/28/35 IS lenses). But if you find a nice one refurbished at your photo-related store of choice (though Canon often has factory refurbished stuff go on sale every couple of months), its worth a shot since it only costs <$500.Edited by verovdp - 4/10/14 at 5:37pm