Checking for front/back focus issues

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gowhow
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p.1 #1 · Checking for front/back focus issues

After reading (probably too much) about lens issues, I was wondering how best to check my current lenses.

I had this idea of a "V" arrangement, with numbers along the edge of the "v"

The V would be placed on its side, with the camera staring through the open end of the V towrds the point (am I making sense?)

Anyway, you woudl make a note of the AF point you think you are focussing on, and then compare with the actual shot

This may be a load of nonsense, but if it isn't, anyone done something similar?

Or is there a tried and tested way to acurrately check whether OOF shots are faulty gear or "no idea" on the part of the photog?

For info, I have a Sigma 10-20, Canon 50 1.8, Canon 70 200 F4L, and a soon to arrive Canon 24-105 f4L, to replace my outgoing 17-85 IS kit lens. Oh, and a 40D

Cheers

Aug 29, 2008 at 10:37 AM

therock
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p.1 #2 · Checking for front/back focus issues

Get ready for a test chart link.

Just go out and shoot. 75% or more of the ime it's behind the camera than in the camera. Trouble, the easiest thing on earth to find, if you look for it you will find it every time.

I loath the test chart, lots of folks worship it. For it to be accurate you have to set it up in a lab using a transit or you can forget about it's accuracy.

Go out and shoot. Look at you work in Zoombrowser to see how you are placing your focus points.

Posting sample will get you the best help from the good folks here.

Aug 29, 2008 at 11:21 AM

Alistair Watson
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p.1 #3 · Checking for front/back focus issues

I will side with therock on this. I think focus test charts are a waste of time, though here is one anyway. http://www.focustestchart.com/

If you shoot at a wide aperture regularly then I think you just know the lens or body is off and back they go to Canon.

Aug 29, 2008 at 11:50 AM


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