Camera Labs

(note thread title has been edited since original posting)

If you look at used kit dealers you might see older Sigma lenses as being described as being incompatible with newer cameras, probably due to the chip inside having out of date code. Question is, what happens if you try using one?

Particularly on Canon mount, I just got a 70-210 UC-II. In a quick test shot it seems to be ok, but AF doesn't work. It makes a bit of a humming noise and sometimes twitches, but it isn't AF-ing. Being a Sigma, I also have to wonder if its more likely mechanical. Tried on 300D and 5D with both doing same, usable in MF. Seems sharp at 210mm f/5.6 so might not be a paperweight.

If I'm really bored, I might take it apart at work... I didn't have any particular need for this lens, came in a bundle of other stuff off ebay.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Just tried to use the Sigma lens with the film camera. It still doesn't AF, although it makes more signs of movement at times. Guess it's just simply broken and I have something to poke around the inside of later.

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

I have partially opened the lens now. The stuff at the top of the image is part of the AF drive mechanism. The small wheel drives the bigger one, which is coupled to the motion detector and onto the rest of the mechanism. I suspect the drive belt is too loose now. It is very slack, so when the small wheel turns, it can't grip enough to move the big one. The lack of motion picked up by the sensor then tells the motor to stop trying, hence no AF. I think I need to find a replacement belt...

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Very interesting, keep us posted

You seems to get a lot of toys on your hands