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| p.6 #14 · DotTune: New AF tune technique, no photos required |
Finally had some time to play with this, using the Nikkor 14-24/2.8 . Used a FoCal target, tripod mounted the camera, and made sure that center AF point was in-line vertically with the center of the target, and that the camera was level.
The 800e seems to be spot-on, so I didn't try many variations.
The 7100 is a different story, apparently. I set the lens to 24mm, did a LV focus, and then switched to viewfinder, and didn't get a green dot. I ran the AF tune to -20, and got the green dot. I was in AF-S mode in the viewfinder, and AF-S Spot in LV.
I then turned AF tuning off, and repeated the test at 14mm. Again, no green dot. Set AF on, -20, and no green dot.
Went back to 24mm, and no green dot. Hmmm.
I then checked the instructions, and found that I should have dialed in a + value, as the arrow was pointing to the right. Did so, to +20, and got the green dot at 24mm.
I guess I'll chalk up the first -20 correction working to cosmic rays.
Still didn't get the dot at 14mm.
I then changed VF focus to AF-C, D51. Got the green dot at 14mm. I found that as long as I used more than one focus point, I could get the green dot, repeatedly and consistently.
I also found that if I switched to 1.3 crop mode, AF-S, the green dot would at least flicker.
I then took a couple images, one with LV, one with VF & AF dialed in and focus achieved, and one with AF not dialed in, and VF focus not achieved. Looking at them on my monitors, I can't see a heck of a lot of difference, honestly.
In the WTF category, there's a clear difference in exposure between LV and VF modes. Using Auto White Balance on the camera, LR reports different values for Color Temp and Tint, and LR's histogram reports different RGB values. Not a huge difference, but clearly visible to my eye; more visible than the difference in focus.