homebrew point-source enlarging

Discussion in 'Enlarging' started by Murray@uptowngallery, Sep 7, 2007.

  1. Murray@uptowngallery

    Murray@uptowngallery Member

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    For all the negative, uh, bad things people say about point-source enlargers, there are people who have used them successfully and they seem to offer something unique.

    With an interest in many other aspects of photography that fall by the wayside, I can't help but wonder if it would be fun (dust & scratches aside) to try.

    An occasional mysterious Ektar enlarger or 'color printing lens' shows up on eBay cheap, with a fixed iris. A little research led me to the point source concept and the usual fixed iris nature of such lenses.

    I would probably only do 6x9 negs which I currently scan (some say a scanner acts like a point source enlarger with a diffuser on the lens...hmmm....)

    Alignment, flatness, cleanliness, scratches are the usual things warned about.

    How hard would it be to make a point source head? Are they optically precise points, in other words, is there no end of headaches trying to find a source that isn't flawed in countless ways. How about a flash? Exposures supposedly tend to be short with point source enlarging, but maybe a flash is underkill?

    Does a point source HAVE to use a condensor (to spread the light out?)

    Thanks

    Murray
     
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  2. noseoil

    noseoil Member

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    Murray, hopefully Donald Miller will see this thread and can answer some of your questions. I went to his home this spring to see his in action (he converted his Durst 138 with a 1,000 watt bulb and sufficient airflow to keep from melting everything around it). I brought a decent sheet of film with me, Efke 100 & minimal agitation with pyrocat-had which had printed well on my diffusion enlarger, an Omega D5-XL. All I can say is that I thought my prints were sharp until I saw what the point source setup could do. If you have a good sheet of film, this is a great way to print. Not so sure I'd use it for portraits unless there was a model made of porcelain or with flawless skin. Best, tim
     
  3. richard ide

    richard ide Member

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    Murray

    You do need a condensor set. You also need to change the lamp position each time you change the enlargement ratio. I cannot remember the information source but filament area is most important. I have the head of an Opticopy camera/enlarger which I use. The 500 watt bulb has a filament 3/16" x 1/2". It was designed around a 360mm Componon S. Too fast by far. I think a slide projector bulb would also make a good source.
     
    Last edited by a moderator: Sep 8, 2007
  4. Murray@uptowngallery

    Murray@uptowngallery Member

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    Thank you. I have a 30+ pound Opticopy lens for some project someday, apparently monochromatic.
     
  5. Ian Grant

    Ian Grant Subscriber

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    Murray, I made a point source enlarger back in the mid 70's, I un-earthed the condensor lenses (5x4) 2 months ago, last used in 1986.

    You say enlarger lenses with fixed irises, I had quite a few turret mounted (12+) from a pro lab 2 years ago, all Componons, they have a small additional grub screw which is was set by the Durst engineeer who calibrated the printer. Once loosened or removed the lenses function as normal.

    Ian
     
  6. Paul Howell

    Paul Howell Member

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    The basics of a point source is a clear bulb with a small filament and a condenser set up. I converted a Russian Federal 35mm enlarger to point source just by finding the right size bulb and fixture. I had a lamp shop install the new fixture and bulb. Although I have not seen any listed on Ebay for several years Bessler makde a point source head for its 4X5 enlarger. I only use point source on my older 35mm from the 60s, I dont how well my 4X5 or 6X9 will work with point souce as they developed for cold light.
     
  7. Murray@uptowngallery

    Murray@uptowngallery Member

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    I picked up a spare 6-1/2" diameter Dejur condenser, apparently from a 4x5 enlarger, seller said looks unused. I later learned the enalrger had TWO of these.

    I thought I read that a double condenser reduces the height by allowing allows the condenser head to be placed closer to the negative.

    I wonder if a double condenser has any advantage for uniformity of illumination, and if a single condenser (obviously?) having a longer f.l. than a double therefore might have larger coverage, or if used on a smaller neg, have usable uniformity by virtue of using a portion of it's circle of coverage.

    TBD...