From: Richard Knoppow (dickburk@ix.netcom.com)
Date: 08/14/00-03:13:11 PM Z
At 12:24 PM 08/14/2000 -0400, you wrote:
>Hello list,
>
>I am searching for a lens in the 210 to 270 range to use with a 7x17
>camera primarily for landscape work. I am working in platinum.
>
>I have checked the archives, and noted that the 210mm Zeiss Protar,
>210mm Computar and 240mm Zeiss Dagor have all been mentioned favorably.
>It was intresting for me to note that the 210 Angulon was not mentioned
>in the various archived discussions on lenses.
>
>I have no knowledge of these 'classic' lenses, and was wondering if
>anyone can point me to a source of information on these lenses.
>
>Also, does anyone have other recommendations on lenses to consider? My
>criteria for this lens is that it come in (or can be fitted into) a
>'modern' shuttter (copal), and that it be at least single coated. I was
>initally thinking about the Angulon, but the lack of praise for this
>lens makes me wonder... I have heard the Angulons were inconsistant
>performers, maybe this is the reason it is not considered for the 7x17
>more?
>
>As always, this group is very knowledgeable, thoughful, and generous
>with advice and opinions. Thanks in advance.
>
>---Michael Mutmansky
>
>
Pre 1945 Schneider lenses seem to be highly variable in quality. Post war
Schneider became one of the most reliable lens makers. The Angulon is a
variation of the Dagor type. The power of the elements is reversed and the
outer elements made oversize to avoid vignetting. The circle of
_illumination_ is about 102deg but the circle of good definition is only
about 90deg, not much greater than a Dagor.
The Dagor has claimed coverage of 87deg at f/45. The diffraction bluring
at this stop limits the performance but should not be a problem for contact
printing from such a large format.
The Wide Angle Dagor (f/8 or f/9) has a slightly larger coverage than the
standard Dagor, perhaps 90deg. It is likely a little sharper in the corners.
The f/18 Protar covers close to 100deg at f/45, they seem to be quite
sharp lenses. These were made by both Zeiss and Bausch & Lomb, there is
little difference between the two.
Angulon, Dagor, Protar lenses were designed before lens coating was
available and use cemented elements to avoid flare.
All of these are very old designs. For really good performance you must
look into modern WA lenses. If cost is a problem try to find an older f/8
Super Angulon, these are excellent lenses.
Really outstanding WA lenses are made by Schneider, Rodenstock, and
Nikon. Nikon data is hard to find but both Rodenstock and Schneider have
web sites with catalogue information on them. Schneider's is
http://www.schneideroptics.com These modern WA lenes have the drawback of
being both very heavy and expensive.
Another lens which should be mentioned is the Wide Field Ektar. These are
four-element air spaced leneses of the Double Gauss type. They have
coverage of about 80deg at f/32. The performance is very good. They are
single coated.
Many lenes more than about ten years old begin to get a coating of haze
on the inner surfaces. This makes them very flary even when the haze is not
visually dense. For the most part the haze cleans off easily, the problem
is getting the lens cells open. Many larger lenses have back retaining
caps, these are easy to open. Some have front retaining rings without
slots. These can be gotten off with a circular tool covered with double
stick tape. The performance of many older lenses which are considered too
flary can be astonishingly improved by cleaning them.
---- Richard Knoppow Los Angeles,Ca. dickburk@ix.netcom.com
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