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| p.8 #13 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes |
I must say, I was skeptical with Dot-Tune... But once I did it, I was VERY surprised how good it is. Without a single shutter actuation to boot...
I have tried every single MA process out there... FoCal, Lens Align, etc... They work, but are a lot of work to get accurate results.
After I setup my target outdoors (FoCal target) and got everything aligned on the tripod, I followed the Dot-Tune method. I would live-view focus, carefully switch to MF, and cycle through the MA values. This is very quick once you get a feel for the "range" of your camera. For the 5D3, it appears to be +14 or +15 from either end to the other, so once you find one, you can very quickly get the other value in seconds.
I had my lenses calibrated via FoCal, so I had a baseline to compare with and improve on. First up, was my 24-70 II.
Ran the process at 24mm 5 times, which took about 3-4 minutes roughly. Live-view also has a slight focusing tolerance, so you do get a little variance. I just removed the line or two that was abnormal from the other 2-3. I chose the most consistent pairs of numbers. My final value came out to -2W... My Focal value was -2W...
At 70mm, same process as above. My final value came out to +0... FoCal was 0.5. Easy enough there.
With my 70-200 II, FoCal alwayssssss has a hard time with this lens for whatever reason. Not my specific lens either, as I have tested a few different ones... Either way, my values were +5W and +4T via FoCal. After running this method, I got +4W and +3T. Results look excellent!
With my 1.4x III attached, FoCal had me at around 0 (each result was different) at 98mm and +8 to +12 at 280mm... I ran this method and got -1W and +8T...
I am quite happy to have this method versus using FoCal which was a pain with the software crashing, inconsistent results all the time, etc...
Excellent way to MA your lenses, for sure.
The only "trick" is choosing your end values... For example, at -5 it may give a green dot instantly and beep but if you click it a few times you may get a few delayed beeps signalling you are beyond correct focus lock... So go to -4 and see if it beeps each time instantly. I check each point 5-10 times (quick enough), to make sure. Also, if your MA value is +/- 10 units in either direction you may get beeping all the way up through +20 or -20... That is why it is good to know your camera AF "spread" which is quite consistant. On my camera, it was always around 14 units from min to max, almost always. So if you got a beep at +10 and not +9, you can assume your other end is +24, and your MA value would be +17 for example.