msalvetti Offline Upload & Sell: On
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Thanks. That assumes that the MA adjustment is linear across the range, but I'm not sure it is, and that's why I want to check MA in the middle.
I didn't think I'd have time to test this (I always seem to start MA as I'm losing light), but I just finished adjusting the 70-200 again.
When adjusting MA at the wide end, it doesn't matter what the tele setting is, and vice versa. I'm sure this is because the camera recognizes which end of the zoom range is being adjusted, and it ignores the opposite setting.
But in the middle, it's a different story. Here are my latest results with my 70-200:
At 70mm: +1 and -13, midpoint = -6
At 200mm: +3 and -14, midpoint = -5.5
That looks fantastic, except at 135mm I have +8 and -9, midpoint 0. I achieved these numbers setting both the wide and tele settings to the same value. At +8, if I set the Tele value at a much larger number (say +20), then +8 no longer achieved focus. I suspect the camera was averaging +8 and +20 and getting +14, which doesn't work. If I went the other direction with the tele setting I was able to still achieve focus as long as the average between the wide and tele settings was between +8 and -9.
Now I have to figure out what MA settings to plug into the camera for the 70-200. Seems like whatever values I use, I'll be quite a ways off somewhere. If I force MA to be sharp at 135 (by using +6 on the wide end), I'll be way off below 135mm.
I will probably just use -6 at the wide and tele ends and see how the lens performs in real life. I'm also not sure why the results are so much different than the last time I adjusted this lens.
Mark
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