Paris, Leonard wrote: > This is just an observation. If a lens I own says 18mm on it and it's > really 18.75mm, it's no big deal to me, and I'm not going to start building > a database of the "exact" tested focal lengths.
I am not sure anyone tests many of them these days, anyway. Relying on my memory, increasingly age-damaged, I believe Modern Photography used to do that for lenses they reviewed, and as I recall none were exact. I believe I read in one of the reviews that the "industry standard" was to be within 5% of the rated focal length. So a claimed 20mm lens could be anywhere between 19 and 21. No big deal. Bob - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .