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Re: [Rollei] OT: What is a barrel lens?



At 11:10 PM 05/23/2002 -0400, you wrote:
>   Hi Large format gurus, What is a barrel lens and how hard is it to mount
> on a shutter?  of a  barrel lens?    Thanks    
> 
  A barrel mounted lens is a lens without a shutter. Its mounted in a
barrel with an iris diaphragm much like the lenses for a Rollei SLR. For
large format use there is no focusing means as part of the lens. 
  The advantage originally was cost and the fact that some lenses were too
big for any existing regular shutters. In the case of process lenses
exposure was controlled by means other than a lens mounted shutter. 
    They are used with some sort of external shutter, the simplest being a
lens cap. 
  Barrel lenses can be remounted onto shutters but its expensive. A few
more modern ones will siimply thread into a modern shutter, but in most
instances machining will be required. 
  A simpler method is to use something like a Packard shutter, a simple (I
seem to be using that word a lot) air operated shutter having one speed and
bulb. A more versitile method is to make an adaptor for a large leaf
shutter allowing smaller lens boards to be mounted to its front. Then any
barrel lens up to the clear diameter of the shutter can be used on it. The
diaphragm of the shutter is not used, it doesn't even have to have one
 One can use a Packard shutter this way too but a large Ilex Universal, or
somethign similar, will give some range of speeds and flash synch. Such a
shutter could also be equipped with an iris lens clamp eliminating the need
for separate lens boards for each lens. I have a #5 Ilex Universal which
takes 5-1/4 x 5-1/4 lens boards but have an iris clamp on one board. That
is handy for using, for instance, enlarger lenses turned around backward
for micro work. 
  If one has a camera with a built-in focal plane shutter, like a Speed
Graphic, its necessary only to mount the barrel lens on a regular lens
board for use. Some of the lenses supplied for use on Speed Graphics, such
as the Wollensak telephoto lenses, are barrel mount lenses. 
 The Wollensak Raptar/Optar telephoto  lens is an example of a lens which
will mount directly on a shutter. The cells of the 15" lens will mount
directly on a #4 Alphax, with correct inter-cell spacing. This is not the
case for all lenses, in fact most use different cells for barrels and for
shutters. 
  Because many people don't know how easy it is to use barrel lenses they
often go begging. 
  Some of these lenses are suitable for use on SLR cameras with focal plane
shutters like the Rollei with the addition of an adaptor and probably
extension tubes where the focal length is long. 
- ----
Richard Knoppow
Los Angeles, CA, USA
dickburk  

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