D800 fine focus adjust 🤔

Started 4 months ago | Discussions thread
brodgar Forum Member • Posts: 89
Re: D800 fine focus adjust 🤔

We have two separate issues here. Firstly how to perform an AFFT and secondly the rarely discussed issue raised by Daniel Bliss of light frequency.

I struggled for years with a D800 and the 85mm 1.8G, which you used in your test.

I ended up using LensAlign and following every instruction to the letter and the results became stable. Larrywilson's approach should work very well as a quicky alternative.

However it wasn't enough to address the second issue which I think is the cause of much of the dissatisfaction with the D800. But this is not just a Nikon problem, Canons can show it also. Here is a post I made in 2016:


"Many thanks to all those who responded to my post! After more investigation I will answer my own problem:

I was finding a very large (10 point) AFFT difference in focusing my 50 1.8G and my 85 1.8G when tested under “daylight” and incandescent light. Both of these lenses have a reputation for fairly high levels of chromatic aberration.

I found an article on Bob Atkins’ site and a thread in the Canon area of DPReview. He showed that the level of near infra-red in the ambient light was probably the cause of his focus problems.

I concur with this and now after doing extensive retesting with and without a B+H 486 UV/IR cut filter the difference in AFFT between light sources is now down to only 3 points if I use the filter. The results are quite repeatable.

The light sources used were daylight (outside at about 5800K), daylight inside behind double glazing, 4000K LED, studio fluorescents at 5000K, and tungsten at about 2800K.

The colour temperature of the light is not the issue, I believe it is the IR content which has an impact on the phase AF detectors.

Anyway, if anyone is having a focusing problem that is not solved by other means it may be worth trying out the IR cut filter, especially for lenses with high chroma."


The AF mirror angle must be set properly, and that might be a challenge to get a Nikon or other tech to do it. Then you need to do the AFFT with a IR cut filter.

My D800 and that lens are now perfectly satisfactory in all lighting conditions, and are both long term keepers.

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