focusing on 70-200 f4 l lens

hi just done a focus test on my lenses, all except my 70-200 seem ok but it looks as this one has back focus? can you check my results and give me your opinion thanks..
first two are don at 70mm f4 and 98mm f4

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your angle looks to be kinda high.
How did you get your 45degree. I used an angle finder. I dont think you can take the results into consideration unless you can meet the specs of how its supposed to be tested.

used a set square the angle was 45degs maybe an optical illusion? does it seem back focused?

It looks a little back focused..but your text that supposed to be in seems to be pretty good. So i dont think i would worry much.
my 50mm was way out the text is not in focus at all

thanks runner for your reply, thought as much myself it doesnt seem that far out.how does it compare with other 70-200 f4 results? if its acceptable ill keep it if not ..back to cannon for calibration.

I have had a 70-200 f/4 L with back focusing problems and I can tell you that in your case it´s good, for me the OOF goes beyond almost the two linnes of + - 20 mm in both. So, unless you get OOF problems in your shots, I should keep it. Anyway it´s very easy to see, this lens it´s tac sharp, so go outside with good light, use only center AF and shot. Enjoy and be happy !!!

Your results look better than mine, my lens had a more severe bias to the back. I would be happy if I were you.

thanks for the replys guys ..happy chappy now...ow if i can only find the bright days..typical blighty

I am not sure that you can interpret this as meaning anything until you shoot the target square on.

This is an excerpt from Canon's "Lens Works III" an essay on their auto focus system by Canon guru Chuck Westfall :
"The actual focus sensor arrays are three times larger than the viewfinder marks. A user could put an intended subject in the mark, but if there is a strong detail just outside the mark (but within the sensor area), the camera would focus on that strong detail. This is a source of much of the complaints of the back- or front-focusing -- especially with the "ruler tests." Also, as far as the camera is concerned, a focus lock on anything within the sensor area is good, which sometimes covers more area than the photographer intended."
The reason Canon designs their AF lenses with the ability to manualy overide autofocus is that AF isn't bulletproof. Everybody with a Canon camera really should read this essay.
Good luck.

I can understand if its a little bit front or back..but my 50mm 1.8 was 10mm forward.
its on its way back to canon
here is a pic where I focused right on the black line and between the S and H

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I've posted Mr.Westfall's entire essay in this section for anyone who'se never read it. It's very enlightening reading. Again, good luck everyone.

You should probably just post a link to the essay, unless you have his permission to post.

05Xrunner wrote:
I can understand if its a little bit front or back..but my 50mm 1.8 was 10mm forward.
its on its way back to canon
here is a pic where I focused right on the black line and between the S and H

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Now here is another one I took made a dot 10mm back and focused on that dot. and now the lens is pretty much right on where it should be when focus on the thick black line

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They are still not shot square on and until they are there is little sense in any kind of interpretation.

Hello,

Your focus looks fine to me--maybe a tiny bit to the back. Keep in mind that depth of field is 1/3rd in front of the focal point and 2/3rds behind it. So, you should expect the text on the far side of the focus point to be a bit more in-focus than the text in front of it.