DotTune: Video Tutorial for AF tuning without photographs

Started Feb 18, 2013 | Discussions thread
clarnibass
Senior MemberPosts: 1,082
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Re: DotTune: Video Tutorial for AF tuning without photographs
In reply to Horshack, Feb 24, 2013

OK, I tried again and used your target (which someone has claimed to be unreliable, a bit more on that later).

This time I tested my 50mm lens. I manual focused and auto focused using Live View (LV) a few times to make sure LV is focusing correctly. It was excellent and completley consistent. I found I sometimes had to wait more than 5 seconds, for example it would flicker after 6 or 7 seconds, for example. It stopped flickering for at least 10 seconds at -17 and +15, with +16 being very hard to verify, I got it to flicker once but could also get it to stay for at least 10 seconds.

So conlcusion is either -1 or 0 should be right. I know this lens has focus shift. Slight back focus at f/1.8 and then gets to a slight front focus around f/2.8, where in general with DOF being bigger it's not a real problem IME. I could see the focus shift using a 3D target.

I tested at f/1.8 so it is a little strange that if anything, it's supposed to be -1 if not 0. I'm not sure why that is. Anyway, since +16 was so solid, I'm keeping FT Off anyway since I haven't yet found a lens that really needed it (some apertures might benefit from it just slightly, but overall no FT works better).

I am guessing the 3D target, eventhough the focus point was completely inside a flat surface (by a significant amount), confused the camera... or not.

Re the target, I used relatively decent but not particularly good conditions. I could not make the outer focus points not focus on this target, let alone the center one. The outer and center points just consistently focused on the target.

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