Nikon Auto Focus Fine Tuning Question

[resterc]

Hi,

Just wondering if any sifu has done this before for zoom lens using the dot focus method?

Recently did mine and realize that at full zoom in the figure is very skewed.

For example:

17-35mm lens: from 17 to 28mm i am within the range of -3 to -10 (averaged out) but at 35 mm it is between +5 - +19 (so basically for this lens i either do not use at 35mm or when i do so i have to change the auto fine tune figure).

70-300mm lens: from 70 - 135mm range is -3 - +3 (averaged out) but at 200mm i am at +2 to +16 (technically i can put the setting at the edge of +2 i guess)


This is my first time doing it so i did the test 3 x at each range eg:17mm 20mm 24mm 28mm and 35mm.

Any advice on what i should do for my 17-35mm lens?

 

[one eye jack]

It's better you understand how phase detection works,this problem is present since day one.It begins with precise factory tolerance and alignments.Many times people assume there is something wrong when actually the phase detect has random errors and really will focus within a certain band or range.It all depends on the ambient lighting and Nikon advises not to use AF finetune unnecessarily.
However if you want to calibrate AF then read on.

https://learn.zoner.com/focus-problems-fine-tune-your-autofocus-with-dot-tune/

https://photographylife.com/how-phase-detection-autofocus-works

https://onlinemanual.nikonimglib.com/d850/en/18_menu_guide_06_08.html

http://www.dslrbodies.com/cameras/the-d5d500-blog/the-af-fine-tune-itch.html

 

[thoongeng]

Learnt something new today - dot focus method, thanks.

You might want to take test shots and see if the slight misfocus is visible in actual photos. My feel is that the depth of field at wide angle (for 17-35mm lens) and at f5.6 at 300mm (for your 70-300mm lens) may be enough to mask any effects of minor misfocus. Thus set at 0 for your 17-35mm lens may be good enough (I do old school trial and error AF Fine tune method for my Nikon lenses, most of the time happy to leave them at 0)

Maybe others who have experience with this method can comment further

 

[resterc]

Thanks for the replies.

Great article especially https://photographylife.com/how-phase-detection-autofocus-works which i am in the midst of reading right now.

The dottune was something i came across on youtube

and bro thoongeng reading your comment i think you are right. Some back story: when i first tried the dottune, i realize my lens are all on the -20 and above range on my new camera. As such the camera was sent to nikon for check. I was told that the lens mount is severely slanted causing the focus issue. I sent my 17-35mm along with the camera for the repair so i think it is likely the techs at nikon would have used it along with their lens to do their test before returning it to me.

will try some test shot in the future since i just got my camera back...still waiting for LCD protector etc to arrive since the old ones were removed during servicing.