Archived posting to the Leica Users Group, 2000/05/23

[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]

Subject: [Leica] reason projector lenses are easier
From: "Birkey, Duane" <>
Date: Tue, 23 May 2000 14:10:49 -0500

I'm not a lens designer.. And Sal and Ted have more inside info to leica
than I, but common sense would seem to say.

# 1 projectors lenses are rarely used at either close distances like 2 1/2
feet to 5 feet like camera lenses and aren't used at what we would think of
as infinity either. Generally the focal length is relative to the size of
screen and distance... so designers can figure out normal working distances.

#2 none of the elements float or change position.

#3 you don't have to worry much about designing in lens to film plane
distance.. nor the mechanics involved in it.  For example you can move a
projector lens back and forth about 2 1/2 inches..... try that with a normal
camera lens.

#4 you only need 3 or 4 elements to accomplish what you want as opposed to 9
or 10 etc...

5#  If leica really felt that it takes $2000 to make a great projection
lens....  Don't you think they would make it....  after all, there are some
people in this world who buy it no matter what it costs even if you can't
quantify a difference in quality.

#6 I'm going to be a Leica Pro lens for my Ektagraphic when I go back to the
states.  I'm not going to mount 90mm on the projector.

Duane Birkey
HCJB World Radio
Quito Ecuador
Duane's Photographs of Ecuador