Originally posted by UncleVanya As an example, IBIS for a 28-200 (per this paper) should be set to 75mm for optimal effect.

At least in that case, the optimum appears to be the "geometric mean" (= square root (product of max and min zoom values) ) of the maximum and minimum focal lengths.

Makes sense - as a multiplicative factor, that setting is the same "distance" from the extreme end settings of the lens.

And, of course, if you tend to use your zoom mostly around maximum or minimum focal lengths, you should set the focal length for something in that vicinity.

---------- Post added 06-04-22 at 06:47 PM ----------

Originally posted by UncleVanya As an example, IBIS for a 28-200 (per this paper) should be set to 75mm for optimal effect.

At least in that case, the optimum appears to be the "geometric mean" (= square root (product of max and min zoom values) ) of the maximum and minimum focal lengths.

Makes sense - as a multiplicative factor, that setting is the same "distance" from the extreme end settings of the lens.

And, of course, if you tend to use your zoom mostly around maximum or minimum focal lengths, you should set the focal length for something in that vicinity.