been looking at moving on from the Canon 50mm mk1, and the benefits seem to be small given the outlay required...
Al'
Well there's one in the classifieds but Amazon have them new at £379 and I'm sure I can get Jessops to price match it, theirs is £399. I think after reading about some focussing issues with this lens I'd probably opt for a shop I can march into..
I've got the Canon 50/1.4 and I would not call it anything special. As an upgrade from my 50/1.8 I was underwhelmed. Wide open it is far softer than my 50/1.8 was, rendering f/1.4 of questionable advantage, and while the AF is better than the 50/1.8, it is not a patch on my other lenses that have proper ring USM AF..
I've got the Canon 50/1.4 and I would not call it anything special. As an upgrade from my 50/1.8 I was underwhelmed. Wide open it is far softer than my 50/1.8 was, rendering f/1.4 of questionable advantage, and while the AF is better than the 50/1.8, it is not a patch on my other lenses that have proper ring USM AF. Add to that the reputation for damage to the AF, unless you know the steps to take to avoid that damage, and, like I say, I'm not thrilled by it.
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I agree with this on the AF part - but mine is definitely better quality than the 1.8, wide open and stopped down.
Focussing really is crap. Even on my 1Ds it will hunt back and forth for abiout a second or two before acquiring focus unless the light really is good - but whats the point of having a 1.4 lens if it has f*** all focussing ability in such light? The amazing IQ is the only thing stopping me getting rid of it. I can't describe it..
When I had it, my Sigma 10-20 could focus on pretty much anything - it regularly surprised me just how good it was. Point it at something solid black or white, like a carpet or whatever and it'd focus just as well as on a contrasty object. If the Sigma 50 focussed that well and had comparable, if not better IQ than the Canon.... I might go for it!
I have a Sigma 50mm 1.4. It was front focusing a bit when new, but I took it to Sigma to be set up. It will focus correctly now on my 1D, but struggles sometimes on my 5D. Excellent lens, a lot bigger than the Canon 50mm 1.4.
that may be slightly linked to the age of focussing system as its reasonably responsive on a 1d3
i was considering the sigma when i upgraded from my 50 1.8 to 1.4. eventually i went with canon simply because there was a lesser chance of me ending up with a lemon

Nice to see Sigma making a winner, even if I do own three Canon lenses and a Tamron, eh Trencheel?)
Thanks for all your opinions and Tim for the detail.
Nifkin do you have a link for Jacobs at that price, on their site I see it listed as £379.
I'm not convinced either way yet so I think I'll have a drive to Edinburgh this weekend and have a wander round Jessops and probably Jacobs to have a gander.
cheers