D800 AF-ON and AF-C

Started 5 months ago | Discussions thread
fPrime
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Re: And consider trying AF-C tracking with "Release + Focus" as well...
In reply to primeshooter, 5 months ago

primeshooter wrote:

fPrime wrote:

primeshooter wrote:

fPrime wrote:

I've found that I get slightly better focus accuracy with AF-ON and AF-C on the D700 on static subjects versus AF-S. The AF-C advantage may be true in general for cameras with the CAM 3500 FX module.

Interestingly on the D700, in addition to the above, I've also found even with static subjects that switching to the crosshair 9 point AF-C tracking with "release+focus" can often beat out both single point AF-C or 9 point AF-C tracking with "focus" enabled.

Has anyone else experimented along these lines... using AF-C tracking for static subjects? I'm obviously testing focus performance under extreme conditions to evaluate optimal configuration... f/1.4 lens in low, bad light with medium to high contrast targets.

fPrime

Interesting indeed, I have always preferred the AF-C or AF-S single point never liked the area modes but I can see why folk use them. I guess the subjects I shoot don't move that erratically that I cannot just simply follow them with the focus box and save the bother of switching modes?

I know, it seems that 9 point AF-C tracking would pose a higher risk that an off-axis area of brighter reflection or better contrast might distract the focus in that direction. But for some reason the 9 point AF algorithm seems to work slightly better for me in low light than pure single point AF on static subjects with the D700.

Again "focus+release" with 9 Point AF tracking paradoxically seems to be slightly more accurate than forcing "focus"... exactly opposite what I'd expect. This is the reason I'm interested to hear if anyone else can confirm my test results with their own D700.

I may have inadvertently noticed the same actually. It's like Nikon have made a few mistakes with this body or something? Focus is always more important to me than speed etc.

Agreed on the bias towards focus, primeshooter.

As to what might explain this behavior, the better performance could boil down to less processing delay from when the last AF-C PDAF measurement is made to when the shutter actually trips. Since "focus" presumably requires a longer confirmatory processing loop than "focus+release", using the latter setting may allow AF-C to more surely time the optimal lens focus with the shutter release. I believe the same rationale is the underlying basis for setting AF Lock On to OFF... less AF processing delay allows AF-C to catch optimal focus under tracking slightly better.

fPrime

fprime, which setting do you have, short medium long or off? Which do you find gives more accurate results?

I personally keep AF Lock On to OFF which, according to consensus, provides the highest AF accuracy with subjects that are rapidly change focus distance (like when the target is moving towards or away from the camera). It's my opinion that keeping it OFF doesn't hurt accuracy in static scenarios and may actually help AF-C by eliminating yet another processing load in focus calculation.

In shooting static subjects under medium to low incandescent & CFL lighting at f/1.4 I expect, and get, rock solid AF accuracy even with outer, non cross type, AF points on my D700.

fPrime

 fPrime's gear list:fPrime's gear list
Nikon D200 Nikon D700 Nikon AF-S Nikkor 24mm f/1.4G ED Sigma 50mm F1.4 EX DG HSM Sigma 85mm F1.4 EX DG HSM
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