D800 Focus Theory

Started Apr 18, 2012 | Discussions thread
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russbarnes Senior Member • Posts: 1,469
D800 Focus Theory

I class myself as an experienced photographer. Make your own mind up from my website ( http://www.russbarnes.co.uk ). Point is I know how to focus a camera and lets be honest it isn't too difficult until you get to really wide apertures and then you need to have great technique and be realistic about your results. So I've been convinced that I've got a bit of a dud in the D800 where some of the AF points are concerned, until tonight that is. Interesting I see the same issues now popping up on D800Es too.

I've taken a LOT of test images since the weekend with both the D700 and my D800 and I don't think people are necessarily going to like my conclusions. Forget AF targets - this was focussing on relatively contrasty every day objects.

I did some D800 AF tests at the weekend which showed that the 105mm f/2.8G VR exhibited almost no sign of weakness when using the far left or right focus points. Not quite up to the same level but a tiny bit behind was the 70-200mm f/2.8 VRII. Third place came the 24-70mm f/2.8 and finally my 50mm f/1.4G. Given most people would agree that the 105 and 70-200 offer pretty much stellar performance (and my results makes my Japanese built 105mm VR look like a bargain in today's money) I've taken them out of the equation but I was perplexed on Sunday at the difference between the 50mm at f/2.8 and the 105mm at f/2.8 using the same focus points, and when viewed at 100% it wasn't a close competition. This seemed to prove that all focus points worked though because the results from the 105 and 70-200 indicated no issues.

Tonight I stopped examining every image at 100% view though - the D800 files allow you to see things you shouldn't see and I realise now what I've been looking at. I'm fairly convinced this is now 95% about lens weaknesses at the edge of the frame and about 5% camera (or maybe less).

Looking at the performance of the same lenses on the same objects mounted on the D700 showed me some startling differences:

1. The D700 AA filter is considerably stronger. There's a lot of difference here and just shows how much resolution there really is in the D800 and also how weak that AA filter is after all.

2. As a result, the sharpness displayed by the D800 is exaggerating everything including lens weaknesses at the edges of the frame. In fact when you look at files shot with the D700 at x1 in ViewNX compared to D800 files at x0.5, what becomes obvious is that there is no actual difference at this sort of resolution apart from the AA filter.

In other words, viewing these massive 36MP files when shot with the outer focus points is showing the natural limitations of Nikon's glass. I'm not sure in some cases that it is up to the job after all. Now I know the 50 f/1.4G never made Nikon's recommended list, and I can see why, because on my D700 it does a nice job but those 12MP and stronger AA filter hid its flaws. To a lesser degree the same seems to be true of the 24-70. It will do just fine when viewed at a normal distance and at a reasonable size, but don't go looking towards the edge of the frame, at 100% when shot on the D800 with an outer focus point because you're going to get disappointed.

I have an open issue logged with Nikon Europe but I don't think there will be a fix now or any time soon for anyone because I'm now less convinced that there is anything to fix but Nikon developing better glass and putting out updates for lenses like the 24-70 and 50 1.4G.


 russbarnes's gear list:russbarnes's gear list
Nikon D800 Nikon D500 Nikon D850 Nikon PC-E Nikkor 45mm f/2.8D ED Carl Zeiss Makro-Planar T* 2/100 +5 more
Leica X1 Nikon D700 Nikon D800 Nikon D800E
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