40D front focus. Camera or Lens?

Started Dec 20, 2007 | Discussions
PTO2 Forum Member • Posts: 61
40D front focus. Camera or Lens?

I have taken probably 100+ pictures to verify I have front focus with my 40D and EFS 17-55. If I use live view, the focus is perfect. My question is does that tell me that the lens is fine and the camera isn't focusing correctly?

bogongbreeze Contributing Member • Posts: 826
Unfortunately no...

You will still need to test the camera with another lens or the lens with another 40D to see which of the two is mis-focusing. It could be the camera sending wrong info to the lens or it could be the lens not responding properly to the info sent by the camera.

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OP PTO2 Forum Member • Posts: 61
Re: Unfortunately no...

Dang, I was hoping for an easy answer:)

oldeddies New Member • Posts: 5
Re: 40D front focus. Camera or Lens?

had same issue w/100, 24-70, 100-400... sent camera back, everything OK with nedw one

kjumlauf New Member • Posts: 15
Re: 40D front focus. Camera or Lens?

I'm having FF issues with 40D and 70-200 f2.8 IS. Problem is at 70mm end wide open. Not noticable at 200mm wide open or at 70mm f4. I returned one body thinking it was the problem because I have no issues with this lens on my DReb XT. I tested the second 40D body and it's got the same problem. I'm going to work with it a little longer to see if I don't figure something out but it's looking like it'll need a trip to Canon for service.

Philip Persio Forum Member • Posts: 52
Re: 40D front focus. Camera or Lens?

I just upgraded from 350D to 40D, and I am disappointed.
The 40D has the AF issue with all my Tokina and Sigma lenses.

Apart from my Canon 18-55 kit lens (350D), the 40D just could not focus correctly with all my lenses, which have been working properly with my 350D.

I just got a replacement (Firmware 1.0.5) yesterday and the replacement still has the AF issue with all my lenses except the Canon 18-55 kit lens. With the replacement, only the center point of the 9-point AF sensor can focus properly. The AF of my 40D just cannot work correctly at Automatic Selection Mode or single AF point mode with AF point other than center..

I will update the firmware of my 40D to 1.0.8 and try. I just hope that the AF issue is not due to the new 9-point cross sensor and the problem can be resolved with the firmware update. If Canon does not solve this AF problem for my 40D, my next camera should not be a Canon.

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Persio

Kiddpeat Contributing Member • Posts: 986
If the focus in Live View is good,

neither the camera nor the lense has a focusing problem. Live View is showing what the camera's sensor is seeing through the lense as it is then focused. If it shows an in-focus result, that is what the camera will capture.

Perhaps you are not sharpening, are looking with excessive magnification, or are looking at a jpeg with too much compression.

Kiddpeat Contributing Member • Posts: 986
The problem is with your lenses.

You will have to get the lense manufacturer to adjust the lense. Think about it. The Canon lense works fine, but third party lenses do not. No one said that they would. Working on an older Canon camera does not mean they will work with a newer Canon camera.

Jon Leroux Regular Member • Posts: 181
Re: 40D front focus. Camera or Lens?

I suspected my 70-200 2.8L IS USM was back focusing when I bought it so I ruled out all the other variables, I had a wide variety of other lenses around to test, and well they all seemed fine.

Here's what I did:

-Set the in camera sharpening to max (this way although over sharpened I could easily tell where was in focus)
-Used a good study tripod with a proper head for the lens being tested.
-Set the camera to the center point only, and one-shot AF mode.

-Activated Mirror lockup, with a timer. This helps rule out any in camera vibrations.

-Remote release, again just pushing the shutter with your finger on some tripods is enough vibration to mess up your results. Remotely doing it means the camera is still.

-Made sure there were no outside vibrations that would effect the wall the test target was on, or the floor where the tripod was located (IE: someone walking around shaking the floor, workers using jackhammers on the street vibrating the walls, heat vent blowing your target sheet ever so slightly).

-Make sure that both the camera and the test target are level or at the angle needed to complete the test (Some tests call for 45 degrees for example).

-I measured the distance to the focal plane mark to ensure I wasn't shooting closer then then minimum focus distance (a common problem for out of focus shots with lenses that have a larger minimum focusing distance) and gave some extra space to allow for expansion.
-Once the obvious was accounted for, I took some test shots.

-I then used zoombrowser to investigate them, because ZB shows the active focus point in comparison to the shot, I could then see where it should be in focus.

-After that, I put everything away and felt like a moron for spending an hour being paranoid, turns out the lens was fine and I was the cause of the focus issues.

I wasn't used to the weight of the lens, simple as that. Since then I am used to hand holding it and my technique is a lot steadier so my results are much better now.

Your experiences may vary of course but before you blame the camera or lens, take out all the variables and really do an educated test to see what is really the problem.

Jon

RobertoAvanzi Senior Member • Posts: 1,003
Re: If the focus in Live View is good,

Kiddpeat wrote:

Re: If the focus in Live View is good,
neither the camera nor the lense has a focusing problem. Live View is
showing what the camera's sensor is seeing through the lense as it is
then focused. If it shows an in-focus result, that is what the camera
will capture.

Perhaps you are not sharpening, are looking with excessive
magnification, or are looking at a jpeg with too much compression.

No . If focus in live view is good (I assume manual, of course) and the AF misfocuses, THEN there's a focus problem. It may be the camera, or the lens.

Roberto

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darkLCD New Member • Posts: 14
Re: 40D front focus. Camera or Lens?

Either way, the solution is the same. You should send both camera body and lens to Canon Factory Service.

vadim_c Senior Member • Posts: 1,712
Re: If the focus in Live View is good,

Kiddpeat wrote:

neither the camera nor the lense has a focusing problem. Live View is
showing what the camera's sensor is seeing through the lense as it is
then focused. If it shows an in-focus result, that is what the camera
will capture.

Perhaps you are not sharpening, are looking with excessive
magnification, or are looking at a jpeg with too much compression.

Some people are so good at photography that can tell you the problem without even looking at samples ! Once I knew a guy that tried to tell me over the phone why my TV lost sound !!!

To OP send both body and lens to Canon for service. I had the same problem with the same combination - 40D and 17-55/2.8 It took 3 working days for two way shipping and the service - the problem appeared to be in the body but your case might be different.

Kiddpeat Contributing Member • Posts: 986
Why would you assume manual?

The OP said;

If I use live view, the focus is perfect.

He didn't say anything about manual focus in Live View.

Ed Ellks Contributing Member • Posts: 979
Ignore

Message Deleted

Kiddpeat Contributing Member • Posts: 986
So you had a camera where AF produced,

as verified in Live View, perfect focus, but the actual exposure was bad? You sent the camera in, and Canon fixed this 'problem'? Oh well.

vadim_c Senior Member • Posts: 1,712
Re: So you had a camera where AF produced,

Kiddpeat wrote:

as verified in Live View, perfect focus, but the actual exposure was
bad? You sent the camera in, and Canon fixed this 'problem'? Oh well.

Maybe my English is too bad but I really cannot make a sentence of this chain of words.

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