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Autofocus issue after firmware update ( D800 )
- Thread starter imAvalanche
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dgc4rter
Leading Member
That's OK. Anyway, care to offer what your thoughts would be on my D800/D800E comparison? 
Art Jacks
Veteran Member
Assuming your focus point is in the centre of the two images displayed ? The D800 one seems to be aimed at the dark part of one of the storage containers where the D800e one has a bright handle in the same position which maybe has aided the focus accuracy.
dgc4rter
Leading Member
Focus point, as stated, was on the red "Keep Calm" mug in both cases.
John Motts
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Occasionally the focus assist light from the flash can cause issues. It has been known for an SB900 not to be seated correctly in the hotshoe and send the focus right out.
imAvalanche
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I am starting to think that this might be the reason.. i have tried the D800 today for too many shots with tons of combinations ( lenses, apertures, Focus techniques, recomposing, flash on and off etc.. ) and it was pretty much perfect.. i have no idea what caused this issue that day.
Oh well, my dear D600 saved the day anyway
olyflyer
Forum Pro
I think this is VERY far fetched and highly unlikely. The flash has nothing to do with the focus, except that it is sending out light to assist focus on. If the light is sent somewhere else than the area the selected focus point is on, the camera won't be able to focus at all, unless you have auto area selected, in which case of course, the well lit area is which will be selected by the camera.
Anyway, I doubt that the AF assist got activated in the case the OP is discussing, since the AF assist is not activated unless it is necessary, and in the sample image the ambient light is strong enough for the AF without AF assist.
j_photo
Veteran Member
It's been discussed in the past. I haven't experienced it myself. But I wouldn't dismiss the possibility out of hand either.
olyflyer
Forum Pro
Many things are "discussed" and some time even agreed on which is pure hogwash.
This myth is actually easy to test and bust. All you need is a flash cable. I have one, perhaps I'll do some tests this weekend, but I am quite positive about what to expect... ;-)
j_photo
Veteran Member
I'm envious of you. It must be great going through life all knowing and always right
MisterHairy
Senior Member
I would suggest that it is better than believing everything you read.j_photo wrote:
I'm envious of you. It must be great going through life all knowing and always right
John Motts
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I had a Sigma 35mm f/1.4 which would not focus at all with the SB900 focus assist light - it was consistently miles out, but focussed fine without. This is a fact. It went back.
But I'm sure you know best.
Tommot1965
Senior Member
were you using the sb900 red focus assist beam..or the camera focus assist beam..as its a known issues for b/f focusing using the flash assist beam ..mine will sometimes be ok..mostly not..so I disable the flash assist light and use the camera one only
imAvalanche wrote:
Hello everyone,
I have bought a used D800 and it was spot on at focusing, no issues with any lenses what so ever, i have been really happy with it.. however i decided to upgrade its firmware aware 2 days ago.. yesterday i went and started shooting a wedding and was shocked with the results..
Setup is D800 + 85mm 1.8g and a SB-900.
Here is the full shot, focus point was on the bride's left eye.
Here you can notice how shes not in focus at all, however her friends are perfectly focused..
I have even repeated the shot twice, same results.. i stopped using the D800 and had to use my backup D600 for the rest of the wedding.
any advise on what to do? is there anyway i could downgrade the firmware? this is like a burden after i've been really amazed by my D800..
olyflyer
Forum Pro
Even if the "issue" is discussed, in this image there is no way that the AF assist beam was activated since it looks like there is more than enough ambient light.
BTW, I am not convinced that there is any issue at all, I think this is just an explanation some people are trying to give to focus errors. I can not for my life find any reasonable explanation to any connection at all between the AF assist and the focus error. The AF assist is a light beam which is turned on when the ambient light is not enough for AF. It's a dumb light beam, AF is still done by the camera and is not affected by the beam at all in any other way than it is illuminating the target to assist focus.
John Motts
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So you're saying that either I'm lying or that after being a full time professional for 24 years I don't know how to focus?
olyflyer
Forum Pro
Well, why blame the SB-900 for that? ...and if the flash was faulty or really causing AF errors with that lens, why send the lens back? Or did I misunderstand you?
No, I don't know everything best, but I certainly question quite a few Internet "facts" and unless I see logical explanation I try to confirm on my own, not just believing everything people conclude from questionable results. I also know that there is a lot of AF issues with that lens, at least if I believe what I read about it, and this I can not confirm since I don't have that lens. I do however have several others and also the SB-900, so your "theory" about the flash AF assist causing focus errors is on my list for confirmation. I don't dismiss the possibility, just find it highly unlikely and not logical at all.
BTW, AF assist can some times make focusing more difficult because by throwing that red light on targets which have high contrast, which is normally good for accurate focus, the contrast is reduced, making AF more difficult for the camera.
olyflyer
Forum Pro
No, I am not saying that you are lying. What on earth makes you interpret my posts so ill-willingly? Or are you always this negative when somebody not swallowing immediately without questions something you are saying? The fact that you have been a pro photog for 26 years has nothing to do with it. Even professionals make mistakes, and I assume you are not different from us, normal human beings.
Anyway, what in the above quote is related to how you focus? That quote is about hos the flash AF assist is used and how it is turned on.
John Motts
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Because it was the only lens which behaved like that.
This was as a result of thorough testing, which I do with every new piece of equipment before actually using it in my job.
It may not be logical to me either, but I don't actually know every single aspect of the physics involved.
John Motts
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When someone tries, with the best of intentions, to help a poster out with something that has happened in his own personal experience and someone else comes along and just dismisses it as "hogwash", what do you expect?
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