Focus Confirmation Adapter Not Accurate

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photophorous

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I recently got a few Contax lenses and a focus confirmation adapter for my Canon 450D. The adapter appears to function, but no matter what I do, the lens is actually focusing about 3 inches in front of where the focus confirmation indicates. I've read everything I can find about these adapters and nothing explains this. The adapter shouldn't have any effect on the accuracy...it's just an on or off kind of thing. When I focus manually with my only "regular" lens, a Tamron 17-50 f/2.8, focus confirmation works perfectly...just as accurate as autofocus. But with the contax lenses, I'm consistently about 3 inches front focused. The seller has agreed to exchange the adapter, but I'm not sure it's worth the shipping costs, because I don't understand how that could fix the problem.

I'm thoroughly confused, so please spread your wisdom if you have any.

Thanks,
Paul
 
I have the same problem with mine - even with the expensive adapter. I think that problem is the slop of the Rebel AF system. I have a 400D - when I focus, I notice that the AF confirmation lights up, and if I turn the focus some more - it still lights up! There is too much slop. This is why I recently bought a Canon S magnifier - although I am still trying to figure that out.

This is why I was wondering if Live view would help. I would get a focus screen, but my wife does not want a splitscreen view in the finder, so I can,'t/

Try live view focus magnified and see how that works. (You have the 450, right?)
 
Yes, I have a 450D, and live view works great magnified 10X. You can get it perfect doing that, but it's really not practical unless you're working with a tripod. I've been reading more and I think you must be right about slop in the AF system. I just got my 28 and 135 contax lenses, in addition to the 50 I was testing before, and the results are about the same. I'll probably end up with a split image screen, but I doubt I'll buy it anytime soon. I'll just enjoy my new lenses with some good old film for a while.

Paul
 
Pentax models give a nice beep and visual indicator when in focus with old manual lenses. Not sure about Canon or Nikons.
 
ampguy said:
Pentax models give a nice beep and visual indicator when in focus with old manual lenses. Not sure about Canon or Nikons.
Click to expand...

Canon has the beep and a light, but for manual lenses it only works when you use an adapter that has a chip on it. Mine has the chip, and it causes the camera to beep, but it just isn't accurate.
 
Thanks

Thanks

I knew that Canon's needed an adapter with the right contacts for AF confirmation, but never knew it was accurate or not.

Anyone have thoughts on Nikon AF confirmation with either non AI, or old manual AI lenses? beep, and/or visual confirmation? accurate?

photophorous said:
Canon has the beep and a light, but for manual lenses it only works when you use an adapter that has a chip on it. Mine has the chip, and it causes the camera to beep, but it just isn't accurate.
Click to expand...
 
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