DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
OP Horshack Veteran Member • Posts: 6,390
Re: DotTune: Video Tutorial for AF tuning without photographs

clarnibass wrote:

Yes, same thing

By the way, I didn't have tons of time yet, but I briefly checked my 85mm lens yesterday. I set up a 3D target with a flat area that was significantly bigger than the focus point. I wanted the front and back objects to show where the focus is etc.

What I found so far is that the range was much bigger. 0 got the confirmation dot. I think -7 still got it (I'll check again later), but on the positive side it got to +20 and still confirmed.

Is it strange that the range was so big? You and others seemed to get smaller ranges. At +20 focus was deifnitely not great, but of course some of the back subjects were in better focus. Is it possible that the front and back subject were too close to the focus point, making the camera think it was in focus. Maybe I should start with a flat target first.

I would first try the method again with the focus re-established, in case it was off by just a smidgen. I'd also try a 2-D target as well. If you still get confirmation at +20 try the workaround here. Regarding the width of the range, I wouldn't worry about it once it fits within the +/- 20 tunable range - I've written elsewhere that I think the slop in VF dot is by design; if it were more precise it might prove too difficult to use for manual focusing.

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