Stopping down (was Re: Don Lopp)

[Brian Reynolds <reynolds@xxxxxxxxx>]

Greg Erker wrote:
> 
>   On the subject of stopping down he
> figured that some lenses worked well
> stopped down to f22 or f32 and others
> didn't. This seems contradictory to
> the res=1800/f# or whatever the lpmm
> difraction limit is, but I didn't argue
> with him. He mentioned that some Zeiss
> lens only stopped down to f11. They
> were being honest since it sucked at
> f16. Anyone care to comment on this?
> 

res=1800/f# makes assumptions about the lens (probably that it is
otherwise perfect) that may not be true in real life.

When I was looking around for information about the Yashicamat 124G
before I bought one I stumbled on a web site of lens test results.
Although the lens on the Yashicamat can stop down to f/32 this person
found that the sharpest aperture was f/16.  This apparently match folk
wisdom about this camera.  If anyone wants it I'll try and dig up the
URL.

-- 
Brian Reynolds                  | "Humans explore the Universe with five
reynolds@xxxxxxxxx              |   senses and call the adventure science."
http://www.panix.com/~reynolds/ | - Edwin P. Hubble