Backfocusing? Need second opinion!

tigerotor77w wrote in post #6878845
How do you know if it's the lens that is at fault or the body? (Apart from trying the suspect lenses on another body and the suspect body with other lenses...)

You don't.

xarqi wrote in post #6878885
You don't.

Oh. I guess I have some more testing to do for my own setup, then!

Thanks for the feedback on my tests. I guess it's not really an issue for me on my XT. I guess I can still send it in to make sure. Plus, it would be nice to know that the lens will work on any camera body. And if I sell it again, I won't run into this same problem! Thanks again POTN.

tigerotor77w wrote in post #6878845
How do you know if it's the lens that is at fault or the body?

...or the photographer

Seriously, the previous few posts explained why the tape measure test is invalid. The batteries look OK, but it's hard to tell at that size.

gcogger wrote in post #6884109
...or the photographer

Seriously, the previous few posts explained why the tape measure test is invalid. The batteries look OK, but it's hard to tell at that size.

can you elaborate

Did you focus on the box in the middle of the chart and not the distance scale? It's been designed like that so that the autofocus point is not fooled by any other subjects.

Very rarely will a lens be perfect straight from the factory for a particular body, just send lens + body to Canon and they'll adjust it for you.

tigerotor77w wrote in post #6878845
How do you know if it's the lens that is at fault or the body? (Apart from trying the suspect lenses on another body and the suspect body with other lenses...)

The two times I've sent in my lens and body to Canon they've adjusted the lens to the body and never the body.

Yes the tape measure test is invalid because you can't be sure what the focus points are locking into.

gcogger wrote in post #6884109
...or the photographer

Seriously, the previous few posts explained why the tape measure test is invalid. The batteries look OK, but it's hard to tell at that size.

Point humbly taken about the photog -- no claims to these tests being robust (skirting way of saying I might not have known enough to do them 100% correctly).

I was thinking the batteries didn't look too great -- 3 cm laterally is more than an inch, and if "something" decided that 3cm in front of the plane of six batteries was in focus, I would have thought that something was amiss.

curiousgeorge wrote in post #6884678
The two times I've sent in my lens and body to Canon they've adjusted the lens to the body and never the body.

Yes the tape measure test is invalid because you can't be sure what the focus points are locking into.

Makes sense. Won't use it as a reference in the future.

curiousgeorge wrote in post #6884666
Did you focus on the box in the middle of the chart and not the distance scale? It's been designed like that so that the autofocus point is not fooled by any other subjects.

Very rarely will a lens be perfect straight from the factory for a particular body, just send lens + body to Canon and they'll adjust it for you.

Focused in the middle of the chart, *not* the lines.

I'm worried about sending in the lenses to Canon, I guess, because they're brand new. I guess I'd rather try to get an exchange and see how the exchanged lenses compare, and if they're still off, then send off to Canon.

The issue is, what if the exchanged lenses have some other defect? (Can someone please tell me I'm being paranoid and just suggest what they'd do?!)

tigerotor77w wrote in post #6886654
I was thinking the batteries didn't look too great -- 3 cm laterally is more than an inch, and if "something" decided that 3cm in front of the plane of six batteries was in focus, I would have thought that something was amiss.

I'm not sure what you mean about the battery test shot you posted. The middle battery looks most in focus to me - where did you focus?

tigerotor77w wrote in post #6886654
I'm worried about sending in the lenses to Canon, I guess, because they're brand new. I guess I'd rather try to get an exchange and see how the exchanged lenses compare, and if they're still off, then send off to Canon. The issue is, what if the exchanged lenses have some other defect? (Can someone please tell me I'm being paranoid and just suggest what they'd do?!)

They're in safe hands with Canon, you just need to pack them well. They should pay for all the postage too so you've nothing to lose. Having it cheked by Canon will give you peace of mind that your lens is properly calibrated to the body, otherwise you'll allways be worrying in future when one of your shots doesn't look quite right. If you get an exchanged lens who's to say you won't have the same issue, or something worse. If the battery test and focus chart tests consitently give you the same results (ie back or front focussing but not both) then you really should send it to Canon.

gcogger wrote in post #6887451
I'm not sure what you mean about the battery test shot you posted. The middle battery looks most in focus to me - where did you focus?

Ooops. Wrong thread.

My battery tests were such that one of the front batteries was in focus, not the one I "focused" on.

curiousgeorge wrote in post #6887882
They're in safe hands with Canon, you just need to pack them well. They should pay for all the postage too so you've nothing to lose. Having it cheked by Canon will give you peace of mind that your lens is properly calibrated to the body, otherwise you'll allways be worrying in future when one of your shots doesn't look quite right. If you get an exchanged lens who's to say you won't have the same issue, or something worse. If the battery test and focus chart tests consitently give you the same results (ie back or front focussing but not both) then you really should send it to Canon.

Okay. I'll send in the two "uncalibrated" lenses to Canon, then -- no need to send in the calibrated one, right?

Do I need to send in any examples of photos, or is "lens front-focuses" enough?

Edit:
I just realized that I didn't post my images in this thread, and that my battery tests that I referred to weren't even here. Can you take a look at https://photography-on-the.net/forum/showthre​ad.php?t=614280 and let me know what you think?

well, I was going to start my own thread but thought to first post in here since this thread already has many "visitors".

I also performed the test and the results were,,, well, not good (or maybe doing I'm something wrong).
I followed the instructions, used a construction angle to determine the 45 degree angle (you will see it in some of the pics I posted) and put the lens on a tripod. I used a remote trigger for all the pics. All of them were taken at the lens maximum aperture.

Well, what I notice is that at short focal length my 17-40mm and my just arrived 24-70 are not focusing correctly. This apparent problem diminishes as I zoomed in, the 24-70mm at 70mm was spot on and the 17-40mm at 40mm was also much, much better. same occurred when changing the aperture...

I did the shots as close as possible while still having auto focus (single point) acquiring focus.

As you can see in some of the photos, at short focal length you cannot even read what it says on the target line (although you can read what's well behind it but it is much bigger font also).

How sharp should this lenses be at their shortest focal length and maximum aperture combination ??

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here are a couple of tests more, with my 50mm and my 17-40mm (at their maximum aperture and in the case of the 17-40mm at 17mm

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at last but no least...my 28-135mm at 3.5 and 28mm focal length...

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Hi all,
I may have this problem with my 50mm 1.4, I noticed last night at open wide low light situation about 4-5 feet away from the subject and AF points is in the middle and after the shot the subject was blurry but the back was sharp. Would that be a back focusing problem ?