I have noticed this as well. A sigma lens focuses over about 90 degrees of rotation, and the Canons and Tamrons around 135 degrees.aceflibble said:Grip isn't the issue. The problem with Sigmas and manual focus is the rings aren't very tightly connected to the gearing at the extreme ends, causing the ring to 'slip', giving an almost by-wire feeling of lag. On top of that they have a more limited throw than first-party Canon, Nikon, and Sony lenses, as well as being far shorter-throw than Tamron lenses, resulting in far less precision.HarryFilm said:Almost NO third-party lens will work as good as an original Canon on a Canon camera...BUT...you can do what I've done. You goto your local Dollar store and buy one of those really flexible 2mm thick Silicone rubber kitchen sink mats and cut a two cm wide strip -- or whatever width you need to grab onto!) and make a rubber ring that slips onto the lens. It MUST be true silicone rubber and NOT poly-vinyl plastic! Silicone GRIPS very well. There are adhesives or sticky tapes you can use o ensure the rubber ring STAYS as a ring. When slipped onto your lens, this silicone rubber make for a VERY NICE and EASY-to-GRIP focusing ring that works almost exactly like those used on the high end Zeiss Otus series which I find a very easy-to-manual-focus series of lenses! It's a but ugly looking BUT It Works Great! AND IT'S A CHEAP SOLUTION to a big manual focus issue!
(And, personally, I can't exactly turn up with bits of rubber taped to my lenses. My clients are rather too high-class to tolerate that. Which is another annoyance, because the Sigmas are the classiest-looking lenses out there and would fit right in, if only any kind of focus worked consistently for them.)