"Point Light Source"

Discussion in 'Enlarging' started by Pastiche, Aug 20, 2005.

  1. Pastiche

    Pastiche Member

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    Anyone use such a device? (Beseler, part # p112)
    Im thinking of buying one from ebay... and the claim is that it shortens exposure times, as well as yields sharper prints...
    I can imagine that I understand the physics behind it... point light sources give us the sharpest shadows. . . which is really what we are projecting on to the paper under the lamp house....
    but...

    anyone use one?

    your experiece - ?

    TIA.
     
  2. Peter De Smidt

    Peter De Smidt Member

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    I haven't use a point source enlarger. Here's what I've heard: while they print sharper than condensor or diffuser enlargers, they exacerbate negative dust, scratches and other negative flaws. If you get one, you might try wet-mounting the film, as is done on a drum scanner. This would minimize these flaws.

    If you do get one, please let me know what you think of it.
     
  3. df cardwell

    df cardwell Subscriber

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    Hi Noah.

    Point light ... well, in some types of imaging it was handy, but never has been useful in continuos tone, pictorial photography. I mean, you aren't printing electron microscope plates, right ?

    There is NO difference in the acutance between properly done diffusion head enlargement and point light. Except you'll have a murderous time taming the negatives to print well under point light, and you'll get really good with fine sable brushes.

    Feel free to talk about this off-thread if you'd like.

    don
     
  4. WarEaglemtn

    WarEaglemtn Member

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    "never has been useful in continuos tone, pictorial photography."

    Tell that to Brett Weston. His work sure does look good and he used one.
     
  5. vzatse

    vzatse Member

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    Noah,

    I use the point source for omega enlargers quite a bit and I have handled, but not used, the Beseler version. What I recall about the Beseler point source is that it will not cover a 4x5 negative. In general, enlarger alignment is critical as your lens aperture must be left wide open... stopping down will cause vignetting.

    I checked the eBay auction and the dedictated power supply/rheostat that must accompany the point source head is not pictured nor described. I would question the seller if it is included in the auction.

    Good Luck!
     
  6. df cardwell

    df cardwell Subscriber

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    Wish I could, wish I could.

    OK... I'll say it differently. Unless one is printing images not made by a camera, the negative is of sufficiently LOW detail that Koehler illumination is of no value. A normal, aligned, diffusion enlarger with a garden variety lens will image every particle of grain. Changing to a normal condensor only increases the contrast. Going to a point source, changes the contrast. But it doesn't add acutance, or detail. If you make a negative that suits the light source, you get equal results.

    Printing an electron microscope plate is a different thing. You are enlarging an image that was made outside the optical limits of pictorial imaging, and so the details are much finer.... like ( if memory serves ) a zillion times greater than a great 4x5 neg. So, you need every bit of help you can get. And your technique, not to mention darkroom, has to be fastidious.

    Now, someone who likes to print with a Point Source, fine. Do I think a student will get a benefit from buying one ?

    Negative.

    And I'd love to be able to ask Brett about it. But I'd rather talk about the Porsche.
     
    Last edited by a moderator: Aug 20, 2005
  7. KenS

    KenS Member

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    Noah,

    When 'working', I used one for printing transmission electron micrographs ( a Durst 138S). You may find point light source kind of "fussy" to work with, in that you have to "re-set" the bulb position every time you change magnification. New bulbs can be rather expensive if you blow one overloading power through the variable transformer (guity yer 'onour") and from personal experience, did not work too well with 35mm Ilford Pan F... it seems as if there are "anti-abrasion particles" on the emulsion side which will "leave" white spots on the print. (it took us a while with the SEM to find the cause).

    You must have well aligned lenses that are "good" to use wide open, and an accurate focussing device to see where, within the thickness of the emulsion, you are focussing. If you are "into" low power photomicroscopy you will find the point source light superior for making low magnification negatives with sectioned/stained biological materials.

    However, if you like to see the sharp and well-defined edges of every "grain" that are in the plane of focus, enjoy the investment.


    Ken
     
  8. Pastiche

    Pastiche Member

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    Thanks ALL who have invested in this thread...
    Sounds like this is not going to be my bag...
    Im not an amateur microscopist... but another happy 4x5 shooter...
    and rather than go for the ultrafine detail, I'm WAY likelier to go down on negatives which are dark, contrasty, grainy, and quite possibly intentionaly all scratched up, cut, retaped, burned with cigarets and finaly manhandled in indecent ways insulting to the film's gender. .

    I appreciate all your input Fellas. ..