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40d +400 5.6 Focussing Problem

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Old Thursday 3rd February 2011, 07:44   #1
Mancunian
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40d +400 5.6 Focussing Problem

I bought this set-up new eighteen months ago and generally it has
produced, for me, some pleasing results.
Recently a recurring fault happens during shooting when focus is completely
lost , ie; a completely blurred viewfinder image.
I have found that by moving the lens through different areas : near, far, low and high contrast with the shutter half pressed, brings focus back, usually within 20/30 seconds - by which time the bird is in the next county ! I am aware of the near/far switch on the lens and low contrast situations.
Any input would be most welcome.

Thanks Jim.
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Old Thursday 3rd February 2011, 08:08   #2
Roy C
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Have you tried cleaning the contacts on the lens Jim?
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Old Thursday 3rd February 2011, 09:04   #3
Ashley beolens
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Does sound like a communication issue!
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Old Thursday 3rd February 2011, 16:06   #4
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Thanks for the suggestion Roy, I will try that and post the result.
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Old Friday 4th February 2011, 09:06   #5
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Is it possible that you have C.Fn III-1 set to "1"?
This will abort focus attempts if the AF sensors can't resolve enough detail to decide how to attempt focus. If it is set to "1", try it on "0" and see if the error persists.

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Old Friday 4th February 2011, 10:26   #6
Keith Reeder
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Quote:
Originally Posted by Canon Bob View Post
Is it possible that you have C.Fn III-1 set to "1"?
This will abort focus attempts if the AF sensors can't resolve enough detail to decide how to attempt focus. If it is set to "1", try it on "0" and see if the error persists.
Yep, I was wondering this too.
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Old Saturday 5th February 2011, 11:36   #7
Mancunian
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Smile 40D + 400 5.6 focussing problem.

Thank you Bob for your advice. I did indeed have the C.Fn 111-1 setting on '1' and adjusting to '0' has cured my problem.
Not fully understanding the significance of these settings has led to this situation.
Also thanks to Roy,Keith and Ashley for responding and indeed, thanks to all who contribute to this forum, sharing information and helping others along this most enjoyable but sometimes frustrating learning curve.
I must tell you I was at the point of sending the LENS for repair. !!!!!

Jim.
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Old Saturday 5th February 2011, 16:18   #8
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Glad to be of assistance Jim

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Old Saturday 5th February 2011, 18:16   #9
Keith Reeder
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Quote:
Originally Posted by Mancunian View Post
I must tell you I was at the point of sending the LENS for repair!!!!!
I recently had my my 100-400mm bundled up to send off for repair too. All of the AF modes except the "basic" single AF Point mode had stopped working: All AF Points, Zone, Expanded - they were all dead, and I was 100% certain that nothing I'd done could have caused this across-the-board failure.

It looked and felt like a software issue: I did a hard reset (taking out all the batteries including the "clock" battery), and confirmed the behaviour by testing with other lenses, which were no different.

But... A few weeks ago I'd changed the button I use for back-button AF.

This shouldn't have made a blind bit of difference to whichever AF mode I was using, except that I've got my most-used other AF modes saved to Custom User settings on the main dial: what I'd not realised was that the change I'd made to the back button in "normal" mode wouldn't carry across to the Custom User settings. It simply never occurred to me that this wouldn't be a universal change.

So turning the main dial to (say) C1 to switch to Expanded AF mode automatically switched the back-button AF back onto the button I was using when I first saved the user settings..!

It can happen to anyone!
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