DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
michaeladawson Forum Pro • Posts: 11,562
Re: It doesn't work for me

Horshack wrote:

michaeladawson wrote:

Now on to my real reason for posting. I cannot confirm your finding of a narrow range for "dot tune" when keeping the focus system in AF and using AF-ON button set to AF-ON Only. Using the AF-ON button set to AF-ON Only is the way I use my camera so this was perfect. I was happy when I first read this update. I thought "ah-hah".

So I tried it out. No go. My 50mm f/1.8D lens still requires the entire range for dot tune. And since the lens requires a -10 value according to FoCal the dot tune method is basically not worth the effort for this lens.

Now on to manual focus chipped lenses. I have 3 of these. I have the Nikkor 45mm f/2.8P lens, the Samyang 85mm f/1.4 AE, and the Voigtlander 58mm f/1.4. None of these can be dot tuned using this method. The range on these lenses is way larger than -20 to +20. Yet these lenses can be fine tuned and stored in the lens table.

Thanks for the feedback. If you'd still like to give it a go I'd like to troubleshoot if we could. First, what did you see that indicated the range on those lenses was way larger than -20 to +20?


So I suppose the first thing to say is that we probably need to be careful of misinterpreting words like "way" and "much".  So I'll try and be less subjective in the future.

So was the range I observed "way larger"?  I don't know.  It was larger.  I have no way of determining how much larger.  So as we troubleshoot I will try to steer away from subjective terms.

So what did I observe?  If I achieve critical sharp focus in live view then the green dot is solid throughout the entire -20 to +20 fine tune range.  Remember, this is for my chipped MF only lenses that I listed above.

For my 50mm f/1.8D AF lens I can actually do Marianne's offset workaround and come up with a green dot range of something like -18 to +20.  Barely workable, but workable.  I then can go through your dot tune method and can use find the AF fine tune value by confirming one end of the range.  I saw no reduction in the range by using your new findings of keeping the AF selector in AF mode and setting the AF-ON button as you describe (my normal setup anyway).

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Mike Dawson

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