Lens Testing Sheet

[Croasdail]

Hey - in one of the threads about testing a 17-40L lens, there is a test images done against a sheet of paper that says "focus here" with numbers running up and down the sides. I have tried to find this thread again to find out if this test page is something that can be downloaded. Does anywone know of some standarized testing sheets for testing lenses focus and DOF.

Thanks and Cheers!

[pierrot]

I had seen it, then forgot where, then needed it some months ago, and found it again with the "Search" function.
But don't ask me how I did it, I can't remember? Just try a little harder ;)

[blue_max]

If you have access to a computer and printer, it is reasonably easy to make your own and print it out. Then angle it approximately 45 degrees and shoot for the middle.

I can't help thinking these tests are fundamentally flawed in so far as the centre focussing section is square and covers quite a large area in this instance. Also, focus is two thirds behind and one third in front, so the odds are that the rear will seem better focussed.

If the upper most part of the square focusses, then the results will seem to be back-focussing.

I may be completely wrong, but that's my guess.

All my lenses seem to back focus ever so slightly, so is that an issue or do I allow for it?

Graham

[Croasdail]

So far this is the only one have found but it is not the one I was looking for...

http://medfmt.8k.com/mf/USAF.pdf

[slin100]

I can't help thinking these tests are fundamentally flawed in so far as the centre focussing section is square and covers quite a large area in this instance.
Correct. Focus tests should be done using a flat target as in this one.
http://www.canon-dslr.com/Canon_Jan05/Canon_SLR_Focus_Test.htm

Also, focus is two thirds behind and one third in front, so the odds are that the rear will seem better focussed.

Not true. At close distances, where most focus tests are done, focus is roughly half in front and half behind.

[Croasdail]

This is more what I was looking for...... attached is the link

http://www.hkdotnet.com/FrancisPhotographyChannel/AF_Test/AF_test_chart-a4.bmp

and this link tells how to use it...

http://www.hkdotnet.com/FrancisPhotographyChannel/AF_Test/

If anyone has a better test - I would love to see it.

Thanks!

[blue_max]

Not true. At close distances, where most focus tests are done, focus is roughly half in front and half behind.

Apologies if I was incorrect. This was just my understanding. Does it vary according to distance?

Graham

[slin100]

This is more what I was looking for...... attached is the link

http://www.hkdotnet.com/FrancisPhotographyChannel/AF_Test/AF_test_chart-a4.bmp

and this link tells how to use it...

http://www.hkdotnet.com/FrancisPhotographyChannel/AF_Test/

If anyone has a better test - I would love to see it.

Thanks!
The chart is fine but don't follow the instructions. Use it in conjuction with a flat target as described in the link I posted earlier.

[slin100]

Apologies if I was incorrect. This was just my understanding. Does it vary according to distance?

Graham
No problem. Yes, near and far DOF ratios vary according to distance.

[blue_max]

So for macro, presumably there is more depth of field in front?

Graham

[Jon]

So for macro, presumably there is more depth of field in front?

Graham

Need to be carefull about our phrasing here. There will never be more DoF in front of the subject than there is behind it. But, the amount of DoF in front will approach the amount of DoF in the rear as you approach closest focus, whatever that may be.