The Canon EF 100mm f2.8 macro lens mark 1 was released along with some of the very early EF film cameras. It has a 52mm filter thread and the lens extends as it focuses which can cause issues when shooting very close up. This lens is not USM which is one of the differences between it and the Canon EF 100mm f2.8 macro lens mark 2. If you see a Canon EF 100mm f2.8 macro lens advertised that does not have the distinctive gold USM banding around the lens barrel then it is the mark 1 version.
|Photo of Canon 100mm f2.8 macro MARK 1 (Note no USM logo)|
Canon EF 100mm f2.8 macro lens mark 2 was released in the mid 1990s to replace the mark 1 version. Unlike the mark 1 it features a USM motor and internal focus so the lens length does not vary as you focus.
Canon EF 100mm f2.8 L IS macro lens mark 3was released in 2009 and is the first Canon lens to feature their new IS Image Stabilisation mechanism. This is an L series lens unlike the first two versions and with a price tag to match.
Either the mark 2 or the mark 3 versions of the Canon EF 100mm f2.8 macro lens are ones I would recommend. The mark one version has too many drawbacks and is too close in price to the mark 2 to make it worthwhile in my view.