Df Autofocus: A Simple Test

Started Jan 7, 2014 | Discussions thread
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Shotcents Veteran Member • Posts: 4,472
Df Autofocus: A Simple Test

Since I own both the D800 and Df I was curious to see at what point the Df AF module gave up and where the D800 would still work.

This setting is lit from 10 feet away by a single shaded 40 watt CF bulb. It's casting a color. The Indian doll is actually darker than my skin. I expect the EXIF data will make it clear how dark this really was.

This is roughly what the setting looks like to the human eye:

There is no bar or church interior darker than this. The Df and D800 were able to lock on this figure instantly even as I moved it to darker areas. There was no dicernable difference in the speed of the AF acquisition.

Here's the OOC shot

Eventually, by moving the doll to darker and darker areas, I finally found a lack of light where the Df FAILED to lock focus. In tried twice and gave up. It could not focus without the IR of a flash head, since it has no built in illuminator.

Now I tried the D800 and found that after a couple of tries it finally locked focus properly. Impressed and feeling satisfied (my D800 AF is supposed to be better, right?) I tried again with the Df and it failed again.

Next up: Human subject, same lighting and both cameras locked instantly. My wife is very light skinned, so I'll have to try this with a dark subject in a couple of days.

And no, there's no light to read; she's just sitting still for the shot as my son flicked the overhead light off! She is less illuminated than shown in the 1st shot as she's a few feet further away.

Realistically, the shot is absurd. She's sitting in the dark and the sensor is really "lying" with this result, but this is the sort of ability we covet for high ISO shooting.

Because of the light skin I could not find a spot where the D800 would work and the Df would not. And again, I know of no bar or wedding that would be this dark, so I'm truly trying to force the issue.

Next up I pulled out another Indian artifact and this one is very dark grey and medium gray elements. I decided to try setting the lamp back a bit and here I found that the Df had a bit of trouble, though it always locked, it fished for focus a bit longer. The D800 fished only once and locked slightly faster. I repeated the test and again the D800 locked faster.

So what is the difference between center point AF on the D800 and Df??? In practical terms I'm not convinced that it amounts to much. I certainly have not performed an exacting test. On Xmas evening I shot with it at a party in all kinds of bad lighting and the Df never missed once. That's a better test and the Df passed.

So for me, the bottom line is simple: I'm happy with the Df focus ability given my intended use for the camera.



 Shotcents's gear list:Shotcents's gear list
Nikon Coolpix P7700 Nikon D800 Nikon D5200 Nikon D5300 Nikon Df +11 more
Nikon D800 Nikon Df
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