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| p.25 #4 · p.25 #4 · Dot-Tune: Autofocus Fine Tuning in under 5 minutes |
1. Is it normal for the range to be say +10 through -10?
I currently have a total of 84 AFMA registered settings, between my four Canon DSLR and sixteen tested lenses (plus two Extenders). My outer bounds for AFMA are +10 to -6. Forty-two of the values are zero, and all but two of the remaining values are within +5/-5.
2. I notice when I let go of the half shutter press that no any zoom lens I can hear the motor engage and disengage and then when I press the shutter again it will reengage again (hopefully that makes sense)
There are at least two things that might be going on here. If you have AF controlled by the shutter button (instead of a back button), this might be activating and deactivating the AF, although it probably shouldn't make a 'new' noise if you release the shutter button when it's already in focus. Also, if it's a lens with IS, then that will turn off and on, with some time lags between pressing and releasing the shutter button.
3. Are the results similar if I am shooting in dimly lit room (I.E Iso 200 2.8 1/20th?)
The AF accuracy in low light will vary widely with the camera you're using. My 1DX and 6D are about the best you can get from Canon, and generally work pretty well, especially if you can find a convenient light/dark transition line near where you want to focus, and you're using a relatively fast lens. IOW, I don't think the AFMA values will vary in low light, rather the overall accuracy of your AF will vary, sometimes considerably depending on the camera and lens.