The difference between infinity and 1:1 is the focal length of any lens, by definition. I had blocked the lens (with tape) in the infinity position (verified by looking through the finder) so - more precisely - I should have stated that what I measured is the focal length in the infinity position. With internal focusing, away from infinity, the lens effectively becomes 'a different lens'. So it may well be that when set to closer distances the focal length is different... but at infinity it is significantly less than 90 mm.
The short end of the lens seemed to be o.k., but at short focal lengths it becomes difficult to adjust the lens to exact 1:1 magnification, so I did not measure this. Sven Zitat von Pat White <[EMAIL PROTECTED]>: > Sven, I'm not familiar with your measuring system, but are you able to check > the focal length at various focusing distances? Some internal focusing (IF) > lenses are known to have shorter effective focal lengths at shorter > distances. The FA 28-200 is around 180mm at infinity, but more like 110 mm > at around 2 meters, as tested by Keppler at Popular Photography. > > Most other Pentax lenses are much closer to the specified focal length. > Thanks for the info, Sven, it is of interest. > > Pat White > >
