1d MK4 AF

While keeping in mind that I have only had two days out with this body I still have a question about Auto Focus for the 1DMK4 - well it seem very slow and has a habit of not focusing at all. I'm using the shutter button for focusing.

Scenario - I have a number of ducks out in front of me - more than 10 meters - and I have set the lens to 10+ meters. I focus on a duck then switch to another duck near by but the camera will not focus, remaining as if focused on the other duck. I press the shutter and get nothing, no attempt to focus. I press the shutter again and no focus. I then point the camera onto something big, like a tree or building, and it will focus sometimes. I had the Al Servo tracking sensitivity set half way from slow to 0. I changed this to half way beween 0 and fast and have seen no improvment. Other times it seems to work well. Why the inconsistency?

All opinions welcome

Thanks Tom

Thanks Peter - it is only 2 months old. I only have the one lens 500mm which I use with an extender. It does not seem right I may take it in.

Thanks Tom

My MK4 hs never acted like this. I would take it in and have it looked at.

before concluding the camera is defective set the focus range to full and set the "focus search" option to ON and try again.

There are several settings that could be producing this so I agree, don't assume it is defective until you get to know the AF system and what all the Custom Functions mean. Look at Custom Functions III-2 and III-4. Also, any AF system will have trouble focusing on certain things. I have had trouble the odd time and have rarely nailed down a consistent reason, however, I have noticed that bright backgrounds can cause problems.

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Originally Posted by arash_hazeghi

before concluding the camera is defective set the focus range to full and set the "focus search" option to ON and try again.

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Thanks I will try this - I do not know the camera well and may just be jumping the gun. I have a trip planed in the morning so will test this out.

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Originally Posted by John Chardine

There are several settings that could be producing this so I agree, don't assume it is defective until you get to know the AF system and what all the Custom Functions mean. Look at Custom Functions III-2 and III-4. Also, any AF system will have trouble focusing on certain things. I have had trouble the odd time and have rarely nailed down a consistent reason, however, I have noticed that bright backgrounds can cause problems.

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Thanks John - I had another situation were I saw a egret coming from 300 meters away towards me with plenty of time to get in focus and again got nothing. This was a white bird on a dark green bg and was not flying that fast. I was panning and was dismayed that the camera did not try to focus. This was with all 45 sensors active.All i got was a burst of OOF images with the bird dead centre in the frame. I was puzzled! Of course I'm still learning about this camera so user error may be a big factor.

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Originally Posted by Tom Rambaut

Thanks John - I had another situation were I saw a egret coming from 300 meters away towards me with plenty of time to get in focus and again got nothing. This was a white bird on a dark green bg and was not flying that fast. I was panning and was dismayed that the camera did not try to focus. This was with all 45 sensors active.All i got was a burst of OOF images with the bird dead centre in the frame. I was puzzled! Of course I'm still learning about this camera so user error may be a big factor.

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Tom, using all 45 sensors might be an issue if you do not get your center point on the bird once you start focusing. It would be easier to use the center point only (with expansion points left/right of around id you wish), as this will increase the accuracy.

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Originally Posted by Clemens Vanderwerf

Tom, using all 45 sensors might be an issue if you do not get your center point on the bird once you start focusing. It would be easier to use the center point only (with expansion points left/right of around id you wish), as this will increase the accuracy.

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Yes you are proberbly right Clemens. I switched to rear button focus this morning and had a much better morning. Focusing was more fluid - user error may have been the issue. Human nature to blame ones tools.