Archived posting to the Leica Users Group, 1996/09/14
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On 14 Sep 96 at 15:51, D Khong wrote:
> My 90 summicron has "05" engraved. Should the actual focal length be 90.5mm
> or 89.5mm? There must be a simple way to decipher all these numbers.
>
> Dan
Assuming the deviation is within 5mm, 00-45 means a longer focal
length, 55-95 means a shorter one.
This raises another question: does anyone have a 00 lens, and what
are the largest deviation numbers among members of this list?
The closer to 50, the more deviation, both shorter and longer.
On a side note: this system is also used on projector lenses, and I
believe more manufacturers than only Leica do this. Pretty sure Kodak
does, since Kodak caroussels are often used in large dissolve
systems.
In dissolve systems, the exact focal length is even more important
than with camera systems; you'd never exactly match the screen with
two dissolving projectors if you didn't pick two identical lenses.
Another very critical application is stereo-photography, for both
taking lenses and projecting lenses.
--
Bye,
_/ _/ _/_/_/_/_/ _/_/_/_/_/
_/ _/ _/ _/ _/ _/ _/
_/ _/ illem _/ _/ an _/ _/ _/ arkerink
_/_/_/
The desire to understand
is sometimes far less intelligent than
the inability to understand
<w.j.markerink@a1.nl>
[note: 'a-one' & 'en-el'!]