[LargeFormat] Old vs New Glass (was Re: Rapax shutter CLA)

[Clive Warren]

At 07:18 02/03/01 -0800, Les Newcomer wrote:


>Clive Warren wrote:
> >
>   The 12" Commercial Ektar sitting here is used for some portraiture
> > - but not for the female of the species, it's just too truthful :-)
>
>
>  Yeah I made the mistake early on of doing some available light
>portraits, unfortunately there was a whole lot of light available so I
>used my f2.8 7.5" aero ektar. <shudder>  Talk about brutally honest!
>
> > Tell me more about zone plates!
>
>At the other end of the spectrum is the zone plate.  From  "pinhole
>Photographery Rediscovering a Historic Technique":
>
>A zone plate diffract light, consequently zone plates are closely
>related to pinhole photography. Zone plate render soft-focus imgagery,
>yet they are not like soft-focus lens imagery. The beauty within a zone
>plate image is the recognizable halo or glow that surrounds any strong
>contrast edge. this glow occurs becuase light rays are considerably bent
>when hitting the edges of the opaque ring within the zone plate*.
>Foliage such as green leaves under certain lighting conditions may
>resemble infrared imagery.
big snip

Les and others - thanks very much for all of that information. Now have 
another project to consider!

Am interested in your use of the Aero Ektar. Picked up one of these a while 
ago in a junk shop here in the UK but have not yet used it.  Thought it may 
be an idea to use a geiger counter on it first as it uses rare earth glass 
that sends out a steady stream of (alpha?) particles.  Currently it is in a 
corner of the room and waiting for an opportunity to mount it - probably 
for use with strobe and no shutter or on a Speed Graphic......

Zone plates sound an excellent for particular subjects and I have an idea 
on using them which may be quite interesting.  Portraiture must be quite a 
challenge with such slow apertures.  There is an excellent device in the 
Royal Photographic Society museum in Bath which could be quite useful - a 
stand which is placed against a chair to keep the subject rigid. The top of 
the stand extends to the head and neck of the subject bit is thin enough 
that it is kept out of the photograph.

Maybe zone plate images are such that subject movement does not matter too 
much!


All the best,
                 Clive   http://www.f32.net
                         Large Format Travel and Stock Photography