sigma 90mm f2.8 macro

Steve Balcombe wrote:

ken wrote:

well it dosnt say di on it so i guess the older one

I think Jay (like Gautam) has assumed you meant the Tamron 90mm macro, because it's the only 90 mm macro lens currently available. I'm saying this because the DI question refers to Tamron, not Sigma.

However I suspect you do mean the long-discontinued Sigma 90mm macro and haven't made a mistake. If so, I'm afraid most (possibly all?) Sigma lenses of that vintage don't work correctly on Canon DSLRs.

The reason apparently is that Sigma doesn't licence the communication protocols in Canon's EOS technology, instead it reverse-engineers them. Reverse engineering is a jargon term for educated guesswork - this means that while Canon has ensured backward compatibility with every EF lens ever made, there can be no such assurance with Sigma. As Gautam explained, Sigma used to replace the electronics in their lenses to make them compatible with present-day cameras, but I haven't read of anyone having that done for a long time.

Knowing this doesn't put me off buying Sigma lenses by the way - I have two - but it is important to be aware of it when buying used, or banking on using an old lens you have left over from a film camera. And buying Canon is not a guarantee of backward compatibility - all the Speedlite flashes prior to the EX series don't work with DSLRs.

The Sigma 90mm is the predecessor of the Sigma 105mm macro. I have a manual focus one from my old Olympus OM film SLR system. It was a very nice compact macro lens, solidly built and with very nice image quality. I think the problem is that it only went to half-life size and you had to use a converter (powerful close-up lens) to get to 1:1 (life-size) - well at least this is the case with mine. As it is such a nice little lens I thought of getting one of the cheap used EOS fit ones you see advertised. However, I found out that it was one of those Sigma lenses that doesn't work on the newer Canon DSLRs. I'm not sure if all the older EOS fit Sigma lenses don't work on the Canon EOS DSLRs, but certainly on some of the well known ones like the Sigma 300mm f4 Apo and 400mm f5.6 Apo this is a known problem. Sigma did re-chip some of these lenses for a while and so these ones will work with the Canon DSLRs, however after a while Sigma stopped re-chipping them and the necessary chips are no longer available. I think these Sigma lenses worked on some of the first Canon DSLRs, but then Canon changed their lens/camera interface, and while it didn't cause problems with Canon lenses, it did with some independents such as Sigmas.