Measuring Focal Length -
70-200mm VR
Prepared 2006-04-19 (146/58663) by Bill Claff
According to my analysis the range at infinity is 72-195mm.
The focal lengths at closest focus are a surprise: 81-205mm.
In other words, focal length does not decrease as you focus closer, it
goes up slightly; focusing is achieved almost entirely by (internal) extension.
Extension at closest focus was 5.5mm at 70mm and 37mm at 200mm.
Highest magnification was .181 which closely matches the spec (.18).
This is the first zoom I have measured where focal length was largely unchanged
during focusing.
I suspect this correlates somehow to the success of this optical formula.
(I imagine that focusing largely by extension requires less sophisticated
correction.)