New Sigma70-200 f2.8 OS or Used Canon f2.8 IS Mk I

Sorry if this has been done before, I did search but I'd like some opinions based on experience if possible.

I've been looking for a telephoto zoom to complement my Canon 24-70L. I have the option of buying a new Sigma 70-200 2.8 OS, for €970 or a used MK I Canon 70-200 2.8 IS for €1,000.

I've read that the MK II is significantly better than the Sigma, but what about the MK I? Would I be better off buying a new Sigma with guarantee or is the IQ and Focus of the Canon that much better that it makes more sense to buy used?

Also how do these compare when used with their respective x2 telecoverters? I can pick up a used MKIII Canon for €400 whereas the Sigma is €290. I can see myself using the teleconverter fairly regularly so it is important to my decision.

I appreciate any feedback.

IQ of the sigma is better than that of the Mk I. The focus of the canon will be faster, and the build is nicer.

Unless you are really into pixel peeping- the Sigma should be fine. Even with pixel peeping- it's pretty good. It's a very good lens- a lot of bang for the buck. Wide open, it's OK. stopped down by 1/3 or 2/3 stop, it sharpens up right nice.
Like any other f/2.8 zoom, it does well with its own TC's. Obviously, the 1.4x TC is better than the 2.0x TC. With the 2.0 TC, stopping it down a bit more- like towards 7.1 or 8.0 helps. It's not that it's bad bad- its just sharper at 7.1 or 8.0. with the 2.0 TC, give it a lot of light.

The build on the Canon v2 is nicer, but it is also physically bigger, focus seems a little faster- but not that much, definitely more solid- like heftier. Until I got the Canon, I never had issues with any aspect of the Sigma.. Still use the Sigma too though. Should get rid of one or the other, but for now, I am keeping both.

does anyone know if the Sigma 70-200 OS will fit on the Canon 1.4 extender?

Owain Glyndwr wrote in post #14655697
does anyone know if the Sigma 70-200 OS will fit on the Canon 1.4 extender?

Yes it will fit every Canon extender. I used mine with the new 2x III for a while (but ended up keeping my Sigma 2x)

When I was searching, I found a used Canon (MKI) for about $200 less than a new Sigma. I decided I would rather have the Canon and $200. I did get to see the condition (about as close to new as you could get) and test it (was very sharp). If the price were the same, I don't know what I would have done. If the Sigma was used and a couple of hundred less than it was, I'd have probably gone Sigma. Both are excellent lenses.

A side note: My three Sigma lenses, are not built like my two L Canons - not even close (but they have been good enough).

The Canon lens has fine optics. Focus is top-class. Depreciation is lower. Whatever marginal improvement the Sigma may see with still objects wouldn't outweigh all that for me.