Re: off-brand lenses they didn't make

[graywolf]

At one time it was normal to rate the focal length to standards even though the 
design came out differently. For instance, the lens on my Graphic is 133mm but 
it is labled 135. It maybe that in their special lenses Pentax desided to simply 
spec them at their true focal length rather than their nomenial focal lengths. 
Then again they may have just decide that odd ball focal lengths where a good 
selling point.

Interestingly and historically; most motion picture lenses were 25, 50, 75, 100, 
150, etc; while still lenses were 21, 25, 35, 50, 85/90, 105, 135, etc. Of 
course; the still range mostly paralelled even older inch standards 1", 1-1/2", 
2", 3-1/2", 4", 5-1/4", etc.

Also prior to the 60's, 21mm was about the widest lens available for 35mm, and 
those were not reflex lenses, but needed a separate viewfinder.

--
Jens Bladt wrote:
Like the K2.8/105mm, if that's an odd ball :-).
Not to mention 31mm, 35mm, 43mm, 77mm, 300mm, 400mm, 500mm, 600mm, 1000mm
1200mm of course.
--
graywolf
http://graywolfphoto.com/graywolf.html