D3 Focussing in low light

[Snapper73]

My D3 doesn't seem to be focussing well in low light, if i'm using my 85mm it takes a wile to lock on to the subject and this is using the focus lock on position (bottom selection) now this only happens more if I just press the shutter button but if I feather tap the button it works better. Is this normal way for it to focus or should you just be able to hold the shutter button down and it will focus. Or is it just to dart for the sensor to see the image

 

[boyfalldown]

It sounds to me as though you're not giving the autofocus anytime to work. Even though the 85mm AF is fgast - its not that fast and if you have release priority set in your focus/release settings this will happen. Giving it a moment, as per when you feather the shutter allows that opertunity.

Hope this makes sense and isn't along way off the mark.

Hugh

 

[Snapper73]

It sounds to me as though you're not giving the autofocus anytime to work. Even though the 85mm AF is fgast - its not that fast and if you have release priority set in your focus/release settings this will happen. Giving it a moment, as per when you feather the shutter allows that opertunity.

Hope this makes sense and isn't along way off the mark.

Hugh

No I think your spot on and to be honest I think i'm just expecting to much from the camera/lens combo

Oh well will have to wait for 85mm AFS

 

[desantnik]

You could try the trick of using a flash (with IR AF assist feature) but turn off the flash firing itself... that works well.

I *think* someone said before that there is a specialised device that does that.

 

[boyfalldown]

I *think* someone said before that there is a specialised device that does that.

don't know if there is a device specially for that, but the Su-800 has the same Af assist functionality without the flash head itself.

Hugh

 

[desantnik]

Maybe it was that then... anyway, my theory is good

 

[Snapper73]

You could try the trick of using a flash (with IR AF assist feature) but turn off the flash firing itself... that works well.

I *think* someone said before that there is a specialised device that does that.

From memory i'm sure my D300 had a little light that helped in this way

 

[desantnik]

Yeah they do, but thats only for the crappy pop up flash and is as limited range wise as the flash itself. If you stick on something like a SB800 or 900 then the AF assist is a little more powerful

 

[Snapper73]

Yeah they do, but thats only for the crappy pop up flash and is as limited range wise as the flash itself. If you stick on something like a SB800 or 900 then the AF assist is a little more powerful

I was using a SB-800 through a soft box and triggering it with the SU-800 Commander so could not use that function on the flash as it was not on the camera.

 

[desantnik]

But the SU800 has AF assist too - as Hugh says above

 

[Snapper73]

But the SU800 has AF assist too - as Hugh says above

AF assist will only work when Auto area AF is used and this is no good when shooting @ f1.4 as you need the focal point to be spot on say on the eye so you have to use single point AF and AF assist is not supported in this mode.

 

[boyfalldown]

AF assist will only work when Auto area AF is used and this is no good when shooting @ f1.4 as you need the focal point to be spot on say on the eye so you have to use single point AF and AF assist is not supported in this mode.

I think the solution to this one is just to give it a moment to autofocus, as above. Af assist does work when a single point AF is selected but it won't work if you're in continous AF mdoe, which you may need to be at f/1.4

Cheers

Hugh

 

[Blapto]

Yeah they do, but thats only for the crappy pop up flash and is as limited range wise as the flash itself. If you stick on something like a SB800 or 900 then the AF assist is a little more powerful

Are you thinking of the Canon cameras? The D300 (and most other Nikons) have an AF-Assist lamp, which is a lamp built into the camera. It's completely unrelated to the flash system.

Canon bodies use the pop-up flash in a sort of stroboscopic blinding mode for AF-Assist.

 

[desantnik]

Errrm could be getting confused there... but certainly the Canon's I've owned have a seperate AF lamp (but its white light IIRC)

 

[boyfalldown]

Are you thinking of the Canon cameras? The D300 (and most other Nikons) have an AF-Assist lamp, which is a lamp built into the camera. It's completely unrelated to the flash system.

Canon bodies use the pop-up flash in a sort of stroboscopic blinding mode for AF-Assist.

No The Nikon flash units and controllers have a seperate AF assist lamp built in. I'm not sure if this is IR or just red light but its not a white light source.
This light is also fired in a sort of 'contrast pattern' and does provide better AF assistance then just the inbuilt white light

Hugh

 

[Blapto]

No The Nikon flash units and controllers have a seperate AF assist lamp built in. I'm not sure if this is IR or just red light but its not a white light source.
This light is also fired in a sort of 'contrast pattern' and does provide better AF assistance then just the inbuilt white light

Hugh

Yes, I know that, destantik said that the light was for the pop-up flash which was what I was confused about.

Errrm could be getting confused there... but certainly the Canon's I've owned have a seperate AF lamp (but its white light IIRC)

Ah, might not be all of them then. It's certainly the case on the 450D and 20D and a few others.

 

[hyakuhei]

Some thoughts on the above:

The AF will take some time to work in low light, you might find that group selection (not full) rather than single point will improve the process.

Most nikon bodies have an AF assist lamp which is seperate from the flash system, it tends to be a white light fitted to the body, I know my D300 has this.

Most (recent) canon bodies do not have an AF assist lamp but strobe the pop up flash to assist focus.

The SU-800 has the same focus assist AF array as the SB-800 and can be used as a more advanced focus assist light.

I have read that it is possible to use the SB-800 as an AF assist without having the flash actually fire, working much like the SU-800 described above.

Hope this helps
-Rob

 

[grey.squirrel]

Carry a tiny torch around with you so that you can shine it in peoples eyes just before taking their picture. Not only will it help with the AF but you'll get some unique and genuine angry moments captured.

 

[SimonTALM]

I know that on the SB800 & SB900 (not SB600) you can definately switch off the flash firing and just use them for AF help. The only downside is that it is quite fiddly to do this and requires some exploration of the menus. The white light is not present on the D3 (although is on the D700, D300, D200, D80, and probably all other Nikon DSLRs other than the top of the range models D3X, D2 etc).

However on the D700 & D300 the AF Assist works in all AF Area modes but only when in Single Shot AF or Manual Focus is selected (i.e. AF Assist doesn't work in Continuous AF mode - had a few panics about my flash being broken in the past over this ). I'm surprised that on the D3 the AF Assist only works in Auto AF Area mode in Single AF and Manual.

I suspect another influencing factor will be the type of AF sensor being used. Of the 51 AF points only 15 are cross-sensors which are the ones that work best in low light when you have an f2.8 or faster lens (on the D3, D700 and D300 these are the ones in the centre 3 columns).

 

[Babaw]

Carry a tiny torch around with you so that you can shine it in peoples eyes just before taking their picture. Not only will it help with the AF but you'll get some unique and genuine angry moments captured.

this made me have a good chuckle!

I've found the AF on my D3 a fair bit faster than on my D300 but even the D3 needs a moment to focus in low light. The focus seems to be achieved faster than the focus indicators in the viewfinder show however. I've only had the D3 since Friday and wow! What a machine!