Canon EF 100mm f/2.8 Macro USM CA and field curvature at 1:1?

Hello everybody, :)

I'm in the process of digitizing my film archives and I'm trying to get the best possible results.
I've been using my 5Ds with an adapter and a vintage slide duplicating rig, consisting of bellows and a film holder.

For this kind of use, the best possible flat field performance is the paramount. Low chromatic aberrations are also desireable

The lens that I'm using at the moment is a Pentax SMC 100mm f/4 Macro.
The Pentax is very sharp in the center with the film grain structure that is clear and defined.
In the corners the grain is still visible, but is progressively getting mushier towards the extreme corners, where it is kind of OK and acceptable, but could be better.

I'm thinking of buying a used EF 100mm f/2.8 USM Macro (the older non L version, since I don't need IS), but it is very hard to find any info on the net describing its flat field performance in the 1:1 range.

Does any forum member have the first hand experience with the old EF 100mm f/2.8 USM Macro in this kind of application - 1:1 copy work that requires the best possible flat field performance and low CA?

Thanks in advance,


CR Pro
Jul 6, 2017
Davidson, NC
I don’t know how relevant this is to your situation, but I’ll respond. I have that lens and have had great experience with it, both by itself and with extension tubes taking it to 2x magnification. I have used my iPad as a lightbox and shot mounted color slides. Results compared well with using my dedicated slide scanner. I find the slide scanner to be more convenient, so I use it instead.
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Nov 3, 2012
I copied thousands of my slides using an EF 50 macro on 25mm extension tube, with a home made slide copier that included an opaque white plastic disk on which I directed my 270EX flash on remote cord. This worked fine and was quite a lot sharper than my father's slide scanner and I found it quicker. More time is spent processing the files, especially dust removal, than actually copying the slides. I had no issue with field flatness. I also had the dedicated Lifesize Converter for the 50mm macro, but that increased the focal length to 70mm, which increased the working distance, something I found unhelpful. I also own the EF 100/2.8 USM macro, but didn't use it for slide copying due to the longer focal length and working distance.
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