Point Light Source? (Richard K?)

http://cgi.ebay.com/ws/eBayISAPI.dll...EBWA%3AIT&rd=1

Is it the real thing?
Sir Richard, can you help?

"jjs" wrote in message
...


http://cgi.ebay.com/ws/eBayISAPI.dll...EBWA%3AIT&rd=1

Is it the real thing?
Sir Richard, can you help?

It appears to be the real thing. Discount the statement
about making poor lenses better, I have no idea where the
guy got that from other than the point source probably gives
the effect of stopping down the lens.
Point source lamps are focused on the entrance pupil of
the lens so the stop does not control the light intensity.
Since the light is very specular at the negative there will
be a very significant increase in image contrast, certainly
for B&W silver images and maybe even somewhat for dye
images. Point sources are used where very high resolution is
required such as in printing microfilm. Point sources are
also used for making very large prints (but not this small
one), and for printing images from microscope or similar
scientific films where high resolution or very high edge
contrast is desired. They will will bring out any blemishes
in the film and also grain so are not the best thing for
conventional printing.


--
---
Richard Knoppow
Los Angeles, CA, USA

In article . net,
"Richard Knoppow" wrote:

"jjs" wrote in message
...



http://cgi.ebay.com/ws/eBayISAPI.dll...EBWA%3AIT&rd=1

Is it the real thing?
Sir Richard, can you help?

It appears to be the real thing. Discount the statement
about making poor lenses better, I have no idea where the
guy got that from other than the point source probably gives
the effect of stopping down the lens.
Point source lamps are focused on the entrance pupil of
the lens so the stop does not control the light intensity.
Since the light is very specular at the negative there will
be a very significant increase in image contrast, certainly
for B&W silver images and maybe even somewhat for dye
images. Point sources are used where very high resolution is
required such as in printing microfilm. Point sources are
also used for making very large prints (but not this small
one), and for printing images from microscope or similar
scientific films where high resolution or very high edge
contrast is desired. They will will bring out any blemishes
in the film and also grain so are not the best thing for
conventional printing.

Thank you, Richard. If I may, I've one more question. The seller claims
that it can be used with a Focomat II as well as the 35mm-only Focomat. I
know the lamp can be made to 'fit', but is his claim reasonable
considering the Focomat II handles negatives up to 6x9cm? Would it likely
work with 6x9cm?

(jjs) wrote in message ...
In article . net,
"Richard Knoppow" wrote:

"jjs" wrote in message
...



http://cgi.ebay.com/ws/eBayISAPI.dll...EBWA%3AIT&rd=1

Is it the real thing?
Sir Richard, can you help?

It appears to be the real thing. Discount the statement
about making poor lenses better, I have no idea where the
guy got that from other than the point source probably gives
the effect of stopping down the lens.
Point source lamps are focused on the entrance pupil of
the lens so the stop does not control the light intensity.
Since the light is very specular at the negative there will
be a very significant increase in image contrast, certainly
for B&W silver images and maybe even somewhat for dye
images. Point sources are used where very high resolution is
required such as in printing microfilm. Point sources are
also used for making very large prints (but not this small
one), and for printing images from microscope or similar
scientific films where high resolution or very high edge
contrast is desired. They will will bring out any blemishes
in the film and also grain so are not the best thing for
conventional printing.

Thank you, Richard. If I may, I've one more question. The seller claims
that it can be used with a Focomat II as well as the 35mm-only Focomat. I
know the lamp can be made to 'fit', but is his claim reasonable
considering the Focomat II handles negatives up to 6x9cm? Would it likely
work with 6x9cm?

Its beyond my certain knowledge. However, if the lamp assembly fits
the enlarger and can be adjusted for the longer FL lens it would work.
The source works by having a lamp of very small area and a condenser
lens which focuses the output at the entrance pupil of the lens. For
most enlarging lenses this will be somewhere between the iris
diaphragm and the rear element. Since you know about how far the lens
must be from the lamp for a given focal length and amount of
magnification you can find out if the thing is capable of focusing
there. A true point source like this must be focused every time the
lens focus is changed in order to have good uniformity of
illumination. On either side of the correct position the light will be
concentrated in the center of the image. The usual condenser enlargers
don't need this critical focusing because the light source is a rather
large and diffused, typically a lamp with an "opal" coating. The more
concentrated the source the more critical the system will be for lamp
focus. Slide and home motion picture projectors use lamps with a very
large area which is imaged on the film so they are also less sensitive
to lamp focus. However, many projectors do have adjustments which can
make a large difference in the uniformity of screen uniformity.
Theater projectors typically have small sources with a condensing
mirror so require careful alignment and lamp focus.
Probably there is someone who reads this group who will have
specific informtion on the compatibility of this source with the
Focomat II.

Richard Knoppow
Los Angeles, CA, USA