Originally posted by newarts How does it "sound[s] the safest"?

It doesn't. I derped. Just ran a few different zoom lengths through it, and it seems too heavily biased by the minimum focal length.

**(2*Min*Max)/(Min+Max)**
18-55mm - 3x zoom: 27.1 (rounded,

28mm)

70-210mm - 3x zoom: 105 (rounded,

100mm)

18-250mm - 14x zoom: 33.5 (rounded,

35mm)

10-20mm - 2x zoom: 13.3 (rounded, 15mm)

**(Min+Max)/2**
18-55mm - 3x zoom: 45.5 (rounded,

50mm)

70-210mm - 3x zoom: 175 (rounded,

180mm)

18-250mm - 14x zoom: 143 (rounded,

150mm)

10-20mm - 2x zoom: 15mm

Really, neither method looks optimal, does it? I guess it's a good thing that (anecdotally) it doesn't matter too much, as long as it's somewhere in the range.