Help with AF Fine Tuning Needed

KSchroeder

New member
I just purchased a 70-200mm, f2.8 VRII lens last week and spent the weekend shooting the lens with my D300. Upon review in CS Bridge and Photoshop, I felt that the focus was just a tad soft... not objectionably so, but just enough to get my attention.

Yesterday, I completed an experiment to assess AF accuracy. In my experiment, I had both a D300 and a D700 body; I had two different 70-200mm VRII lenses, I used two different focal lengths (105 and 200mm), and I approached AF from both close focus and infinity (I manually focused the lens to its closest distance and infinity-- before engaging the AF and taking the shot). I set up a focus accuracy target and shot the target in bright light at a 45 degree angle (per instructions). I took a shot at every possible combination of the variables above (16 shots per body)

The results? Both lenses performed well (focal plane was where I focused) on the D700 body. However, both lenses front-focused on my D300 body... to the tune of about 1/2".

My question? I would like to try to use the Autofocus Fine Tune option in the D300 menu to "recalibrate" the AF. The feature allows you to save a correction factor for up to 12 different lenses, and the camera is smart enough to recognize which lens you have attached, and apply the correction factor automatically. My question is, has anybody done this, and does anybody have any guidance as to how the scale of the correction in the menu relates to actual focal plane shifts. In other words, do I dial in a +2, a +5, etc... to move the focal plane back the 1/2" that I need? I could do it by trial and error, but would appreciate some initial targeting guidance, if it is available.

Thanks!!
 
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