DotTune: AF tune technique without taking photos

Marianne Oelund wrote:

Offset the lens focus a bit, so the AF fine-tune values that give you the two rangefinder transition points will be closer to 0. Then you can determine how many fine-tune values it takes to move from one transition point to the other.

For example, if you defocus the lens slightly so that the AF fine-tune values at the limits of the "green dot" are at +2 and -6, then you know the difference is 8. Half of that difference, or 4 away from either transition point will be the correct adjustment.

Then put the lens back at perfect focus. Find the fine-tune value at the available transition point. Your ideal fine-tune will be 4 values further away from 0; that is, if a fine-tune of -15 brings you to the edge of the "green dot" range, the ideal value will be -19.

--
Qualities possessed by God in infinite proportion: Love, Grace, Power, Righteousness, Wisdom, . . .
Qualities possessed by humans in infinite proportion: Ignorance.