My Backfocusing 70-200 f/4L version 2.

So I did a more controlled test.
Box @ 45 deg. shot @ min focus distance. f/4. ISO 200. 430ex fired. 1/1600.

70mm
http://www.dustincurle​y.net/focus3.jpg

200mm
http://www.dustincurle​y.net/focus4.jpg

just for the heck of it, my nifty @ 1.8
http://www.dustincurle​y.net/focus5.jpg

and my test setup
http://www.dustincurle​y.net/box.jpg


As you can painfully tell, @ 70mm it is FAR worse than 200, and 200 doesnt look that great either. Is this something I should talk to Canon about fixing? I bought this used, and its date code is 2004, so its out of warranty. Is this even something they can fix? Thanks!

Oh, and yes I know its upside down. LOL

29 views and no opinions. dang. everyone must be hungover

I would try the test one more time. This time I would set everyting up as before, Do the test at 200mm first, and then without moving the tripod gently zoom back to 70mm, carefully autofucus, and then then take the shot without moving the camera. You should really be using a cable release to minimize camera movement. The idea behind this is that you will be able to get AF point on top of the thick line better with a 200mm focal length than with a 70mm focal length.

Also try and flatten the target out a little more, it does not look very taught. I can see a shadow cast from the paper not being flat on your setup shot.

A final point is that there should be enough light in the testing area so that you don't need to use a flash, even at ISO 100.

honestly, i would just send it for calibration now, imo there is something wrong with it and it would benefit from a calibration even if it means a few $$ out of your pocket. The more time you spend umming and arring about if it is good or not instead of just getting it fixed for sure gets a little disheartening after awhile, i know from experience

are you right at the limit of minimum focus? that'll be a sure way to get focusing artifacts.

If this lens needs calibration, so does the 50 mm. Therefore, I think it is the body. But you need to make sure by focusing on the bar in the middle, not on the intersection of the bar and the frame surrounding it.

HTH, kind regards, Wim

exactly.
anyone know how much this costs

Ospi wrote in post #4610288
honestly, i would just send it for calibration now, imo there is something wrong with it and it would benefit from a calibration even if it means a few $$ out of your pocket. The more time you spend umming and arring about if it is good or not instead of just getting it fixed for sure gets a little disheartening after awhile, i know from experience

medicdude wrote in post #4610343
exactly.
anyone know how much this costs

If it's under warranty (1 year) then just one way shipping to the factory in California.

If it's not under warranty I heard that the going rate is somewhere in the area of $200.\

Assuming you did the test right there is something seriously wrong with your 70-200 and your body is backfocusing, so you might as well send in the lens and the body if you can't get the testing procedure down to do the diagnosis.

I don't know if the cost for the 70-200 would be the same, but they charged me $95 + taxes and shipping ($118 total). The worse part of my experience is that their calibration didn't help and I returned the lens again. Even though Canon allows you to print a prepaid label when returning, UPS doesn't allow you to add insurance to it and since UPS will only be responsible for $100 on uninsured packages, the label wasn't of any use.

Here's a shot I took with my recently "calibrated" lens:

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