Re: 15" F/11 Red Dot Artar ?

<jjs> wrote in message 
news:13tl7oitj9s7a68@[EMAIL PROTECTED]
>I am getting a 15" F/11 Red Dot Artar (it's on an enlarger 
>arriving soon).
>
> Never heard of such. Has anyone some information on that 
> specific lens?
    The Apochromatic Artar is a very famous lens. These were 
made by Goerz from the early 'teens and continued by 
Schneider after they bought out Goerz American Optical in 
the mid 1970's. I am not sure when the last one was built. 
The Artar was the most widely used process lens in the 
world. It is a four element air-spaced lens of a type 
sometimes called a Dialyte, based on the Celor lens designed 
by Emil von Hoegh, the inventor of the Dagor lens. The Artar 
was designed by Walther Zschokke.
    The characteristics of the Artar are outstanding color 
correction for both longitudinal and lateral color, rather 
narrow coverage angle (typcial of Celor type lenses) and low 
speed. Process lenses are optimized for unity magnification, 
that is, equal object and image distances, however, when 
stopped down somewhat, they have good correction at infinity 
up to a coverage equal to an image circle about equal to the 
focal length. Stopping down does not increase coverage 
significantly with this type of lens. Older, uncoated, 
Artars tend to have some flare because of having eight 
glass-air surfaces, however this does not affect the 
sharpness.
    The Red-Dot series were the last of the Artars, the 
first one being built c.1960. AFAIK all Red-Dot Artars are 
coated.
    Late Artars were available with some adjustment of 
element spacing to optimize them for other than 1:1 
reproduction. In general, the coated versions have some 
adjustment, the shutter versions being adjusted for more 
distant objects than the barrel types. This specifically 
includes the Red-Dot series.
    Artars were also widely used for very high quality 
enlarging before modern specialized enlarging lenses became 
available c.1960's.
    The most common focal length is 19" but 15" is also a 
common FL. Artars were available in focal lengths from 
perhaps 4" to about 70".
    Process photography was the making of printing plates 
for photo-mechanical reproduction. For four-color work the 
three color images must be exactly in focus and of exactly 
the same size, this is what the Artar was designed to do.
    Most barrel mounted Artars have slots for the special 
stops used for color process work and for filters.
    15" is a bit long for enlarging even for 8x10. At 1:1 
any lens covers an image circle that is double its infinity 
coverage. For 8x10 about a 10" lens is adequate although a 
longer lens will give you better illumination uniformity.


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Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]