[quote name='Rainer' timestamp='1289580800' post='4132']
Actually, I also owned the EF 28/1.8 USM ... but not only does it develop more CA than the
Sigma 30/1.4, it also has a massive flare problem. In many situations, the Sigma just
"behaves" noticably better than the Canon. The only real problem is to find a sample
that plays ok with the body you have.
Just my 2cts ... Rainer
The EF 28/1.8 also has fairly ugly bokeh in my opinion - one of the reasons I went for the Sigma 28/1.8
It seems that this is a rather problematic focal length. I've yet to see fast-aperture lens that really shines there.
The Sigma 30mm isn't all bad. It definitely has it's flaws (as pointed out in the PZ review) but not all of those really matter, depending on what you're shooting.
Border sharpness - rarely an issue for me. When shooting at wide apertures, most parts of the image are OOF anyway and when shooting stopped down, the borders get better. On the other hand, the center sharpness of this lens is exceptional. It's very usable even at f/1.4 and really shines from ~f/2 onwards... this is what made me chose this lens over the Canon 28mm f/1.8 (which is worse at f/1.8 than the Sigma is at f/1.4, judging from reviews and sample images).
CA - Depends heavily on the subject. I can only remember one image where I really found this to be a problem. YMMV.
Vignetting - Yeah, there is some when shooting wide open, but not enough that I ever cared about it. Again, personal opinion.
Bokeh - Although the bokeh is usually rather smooth and creamy, it sometimes produces some pretty ugly cats-eye-shaped onion rings in the corners. Doesn't seem to happen at all apertures and is only visible on a couple of pictures, but be aware that this can be an issue.
But guess what bugs me most with this lens? It the barrel distortion, which is (in my opinion) too high for a prime lens. I notice it more than any other optical shortcomings of this lens because you notice it right through the viewfinder every single time you have a (supposedly) straight line in your photo.
So would I buy it again? You bet! Given the lack of decent alternatives in that segment, that is.
Would I recommend it? Yes. But get it at a store with a good return policy because you might need to go through a few copies until you find one with good AF. I was lucky on the first try, though.
[quote name='Azo' timestamp='1289530478' post='4116']
Photozone rate this lens as sub-average (2 stars). I compared it side by side with Canon EF 35mm f/1.4 USM (a $1,600 lens, 4 stars) and I really cannot see from the graphs such a big difference. A f/1.4, 30mm @ $440 looks great for me, but I was disappointed by the review (I am still trying to convince myself to add it to my Christmas list). Maybe Henry's may let me shut some pictures to test it. I would appreciate the opinion of somebody who own this lens. I am interested mostly for the f/1.4 - f/2.8 range since I own a Sigma 17-70 mm that covers f/2.8 and up @ 30 mm.
I think it often comes down to quality control and sample variation. It seems that half of the reviews on the net from testing sites and users say it's a fantastic lens, razor sharp, etc. And the other half say it's not sharp and has focus problems.
I fall into the latter camp. Bought the Sigma 30/1.4 for my Nikons a couple years ago due to the rave reviews and found it unsharp and hazy until about f/4, and even then the corners were still blurry. Only at f/8 did i get a good clean image across the frame. I sent the lens back for refund and didn't want to play the "Sigma Lens Lottery" until i got a perfect copy.