D800 + SB 900 AF Assist On = Back Focus Issue

Started Apr 7, 2012 | Discussions
Darren Francis
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to Rikki, Dec 31, 2012

I'm experiencing a similar issue with my Nikon D4 and SB910.

I never had an issue with my AF Assist when I was using D3S with SB910/SB900.

It seems that turning AF-Assist off seems to give me better results.

Also, I have been having a pretty good success rate with continuous 3D compared to AF-S with AF-Assist on.

I would like to know if there are any other D4 users having the same issue.

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Leonard Shepherd
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Re: I disagree with everything posted.
In reply to D800, Dec 31, 2012

I disagree with everything posted.

The most likely issue is the OP and others have not noticed that the D800 autofocus is different to the D700

Nikon introduced smaller autofocusing detection areas in the D3s. The benefit was less chance of the camera locking onto something away from the centre of the viewfinder autofocus mark, offset by exactly what small detail the new autofocus can accurately detect.

This autofocus change is incorporated in the D4 and the D800.

Based on this image there is no D800 problem, though there is a change in the way the autofocus works compared to a D700.

I leave the few bemused by this comment to read and understand page 100 of the D800 instructions and work out why there might be a problem with small lettering as an autofocus target.

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Leonard Shepherd
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.

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Marcin 3M
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Re: I disagree with everything posted.
In reply to Leonard Shepherd, Dec 31, 2012

Sorry to say, but your post doesn't explain odd behavior of af with afa turned on.

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Jay A
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Re: I disagree with everything posted.
In reply to Leonard Shepherd, Dec 31, 2012

Leoanard, this is a known issue and has existed for months with the 700 and 900 series flash units. It has nothing to do with the D800 autofocus being different to the D700. As a matter of fact, some have reported the issue with the D700 as well.

I myself just have the on flash focus assist turned off at all times and everything works fine. If I turn it on, I am guaranteed to get back focus without fail.

Do a google search on this topic.

Leonard Shepherd wrote:

I disagree with everything posted.

The most likely issue is the OP and others have not noticed that the D800 autofocus is different to the D700

Nikon introduced smaller autofocusing detection areas in the D3s. The benefit was less chance of the camera locking onto something away from the centre of the viewfinder autofocus mark, offset by exactly what small detail the new autofocus can accurately detect.

This autofocus change is incorporated in the D4 and the D800.

Based on this image there is no D800 problem, though there is a change in the way the autofocus works compared to a D700.

I leave the few bemused by this comment to read and understand page 100 of the D800 instructions and work out why there might be a problem with small lettering as an autofocus target.

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Leonard Shepherd
Many problems turn out to be a lack of intimate knowledge of complex modern camera equipment.

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Patco
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Re: I disagree with everything posted.
In reply to Leonard Shepherd, Dec 31, 2012

Leonard Shepherd wrote:

I disagree with everything posted.

That's OK.  Many here disagree with everything you post.

I leave the few bemused by this comment to read and understand page 100 of the D800 instructions and work out why there might be a problem with small lettering as an autofocus target.

Which scenario on page 100 do you think applies to lettering?

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MariusMM
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to D800, Jan 1, 2013

What about the camera AF assist? is it better then to use it or just turn both off flash and camera af assist?

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Russ Hickman
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to D800, Jan 10, 2013

I tried using one of my old SB-800s on my D800 and it works perfectly. The back focus issue I was having with my SB-900s doesn't happen with the SB-800s.

Hopefully there will be a firmware update soon that will fix the issues with the newer flashes because I obviously like them better.

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MacAllan_25
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to Russ Hickman, Jan 10, 2013

That has been my exact experience as well.

The SB-800 with AF assist light works rather flawlessly with the D800E, while both SB-900 and SB-700 produce massive amount of backfocus in the same test conditions.  I don't have the SB-910 to try; I won't be rushing to buy it anytime soon, either.

Interestingly, all three flashguns work just fine with the D700.

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heptagon
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to Russ Hickman, Jan 10, 2013

Russ Hickman wrote:

I tried using one of my old SB-800s on my D800 and it works perfectly. The back focus issue I was having with my SB-900s doesn't happen with the SB-800s.

Hopefully there will be a firmware update soon that will fix the issues with the newer flashes because I obviously like them better.

I guess you just have a good copy of SB800. I have tried two copies of SB800's and only one of them doesn't have any focus shift problem, while the other had front focusing problem.

I have also tried 2 different copies of SB900 and one copy of SB910, both back focuses on 3 copies of D4, one copy of D3s, with one copy of 24-70G, one copy of 85mm 1.4G and 85mm 1.8G.

I guess it's just a general issue but people don't complain much because it's not very visible unless at wide aperture.

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Leonard Shepherd
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Re: to help explain
In reply to Marcin 3M, Jan 10, 2013

Marcin 3M wrote:

Sorry to say, but your post doesn't explain odd behavior of af with afa turned on.

Autofocus generally looks for the best area of contrast.

When the Auto Focus assist beam shines on a subject it is often the area of best contrast, and is likely to present different subject characteristics to the auto focus system than when the subject is not illuminated with the assist bean.

Auto focus efficiency depends in part on what the subject characteristics are. If the subject characteristics change, as they can do with the beam on or off, auto focus efficiency may get better or may get worse.

I do not own the SB910.

Page D 58 of the SB900 instructions explain there are limitations to the focus distance for good results; and also the number of auto focus points used vary according to the focal length of the lens.

It is likely Nikon mention similar limitations when using the SB 910.

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Leonard Shepherd
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Tommot1965
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Re: to help explain
In reply to Leonard Shepherd, Jan 27, 2013

Any news on a fix for this issue. Like others here I have the same problem combo is d800 and I sb700

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An Empty Frame
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Thank you very much for sharing!
In reply to D800, Jan 27, 2013

I experienced the same problem on a paid shoot yesterday. I lost more than an hour trying to identify the problem. (I eventually switched back to my good old D700 ;-))

After another hour trying to find what's wrong today, I found that it was the combination D800-SB900. Thanks to this post, I switched off the AFA and everything works now as it should.

According to my findings it has nothing to do with letters, stripes or whatsoever. I mainly shoot portraits, and I can reproduce it focusing on my daughter's eyes with either a 50mm 1.4 and 85mm 1.4.

I then ask myself: suppose you're dealing with a wedding, in the church the moment they are exchanging the rings and bang you start fiddling...

Grtz,

P.

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rid12k
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Re: Thank you very much for sharing!
In reply to An Empty Frame, 4 months ago

I recently bought the YN568 to go with my recently bought D800 (firmware all updates as of posting), and I have been having the same back focus issue when using the AF-S focus mode.

All focus assist lights on the flash and the camera have been turned off and still get this backfocus. The only time this problem goes away is when I use AF-C mode which is tough to use if one tries to focus and recompose (any suggestions on this welcome).

My brother has a D800 + SB900 setup so I put his flash on mine, my flash on his, and his flash on his D800, and every time at AF-S the same backfocus exists. I am at a complete loss at how this is still an issue considering most people using D800s must also be using some ext flash. So even with the most recent firmware update this still remains an issue. Anyone out there found a solution or workaround for this problem yet?

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exRhodesian
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Re: D800 + SB 900 AF Assist On = Back Focus Issue
In reply to D800, 4 months ago

Hi,

Same problem with the SB910 as seen here:

http://www.dpreview.com/forums/post/51411478

But I don't have the problem with the SB800. Still have to test the SB910 with the D810  - hopefully not an issue.

Thanks,

Adrian

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