Canon 100 f2.8 Macro Non USM...strange focusing problems

Started May 12, 2011 | Discussions thread
AdamT Forum Pro • Posts: 58,589
Re: Canon 100 f2.8 Macro Non USM...strange focusing problems

When I first tried it at infinity (I shot a building about 100 m in front of my window) wide open, I thought "wow it's so soft!!", but actually the lens was front focusing.

Then I also tried it wide open at short but non macro distance (I'd say about 50 cm from the lens) shooting at three batteries with tiny writings on them and the central one was perfectly OK and I didn't notice any ff (or bf)...

I found the same with the one I had a few years back (on the totally dependable 1DS Mk2) and I just decided that the lens wasn't much good as a standard prime because of this and sold it . the Internal focussing 100USM macro is great at both ends of the focussing spectrum ..

Of course the 1DS2 doesn't have Micro-tuning so I Couldn't try the trick you did and the non USM has the ancient Extension focussing with slow AFD motor (much like the Sigma and Tamrons still do) so it's doubtful I'd try another but your findings are interesting all the same .

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