« on: April 29, 2013, 06:54:53 AM »
Other than the OS (Canon IS), I don't see the sigma being a challenger of any sort.
Who knows, though?
The Canon design is an ancient design with blurry corners and a blurry mid-frame. It's not a top of the line lens. It also has severe issues with purple fringing that's very poorly controlled, and as a long lens , lacking image stabilization means if you're just shooting an event or you're wasting 1-2 stops of light just to counteract camera shake without making your subject any sharper.
Here's a comparison between the 135mm f/2.0 and a much sharper lens:
f/1.8 also makes a difference is subject isolation, and also reduces noise too.
Everyone was saying that you couldn't improve on the 35mm f/1.4 before and look what happened. The problem is that people assume a "good" lens can't be replaced by something that is earth shatteringly better.
My old 200mm f2.8 II L was the sharpest prime I have ever used. It was a sublime lens. But I sold it because my 70-200 f2.8 II L IS was nearly as sharp but a lot more versatile. My 135L is sharp and yes it gets a bit of purple fringing....but Lightroom deals with this so well that it's a non issue. My 85mm f1.2 II L is a tad sharper. No one ever believes me when i say this, which I think is an opinion which goes against common forum mantra. But my copy is. My 135L is a stellar performer and I get great result out of it and I use it wide open often.
But it's a an old design and things have moved on. There's a possible 1/3 stop of brightness which can be extracted from the front filter size. IS could easily be added. AF could be tweeked. Newer coatings to help cleaning and flare control. More aperture blades and rounded ones would help the bokeh a bit. It's not weather sealed and mine's been back to Canon a few times for a loose front collar. The Hood is huge and it's flare control isn't as good as other lenses.
It's a bit like the 35mm f1.4, a brilliant lens. But just needs a little update to bring it up to epic status.