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Thread: 20х24" enlarger

  1. #21
    Randy Moe's Avatar
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    Re: 20х24" enlarger

    Everything is compromise.

    I should not have assumed from your location.

    I only meant anything is possible.


    Quote Originally Posted by mamanton View Post
    Thanks! But in that project I mostly believe in German quality ))
    We'll try to do our best in international cooperation!

  2. #22
    Drew Wiley
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    Re: 20х24" enlarger

    Even German products are compromises. That kind of conversation I've had face to face with their engineers and CEO's.

  3. #23

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    Re: 20х24" enlarger

    I graduated from The Rochester Institute of Technology in 1973. Saw a lot of very unique photographic equipment while I was up there. In one room was a really large horizontal enlarger. From what I can remember everything ran on two floor tracks. "Easel" had a box on top that held a roll of Polycontrast paper. There was a light trap from which the paper was rolled down from. Typical lens stage with bellows connecting it to the negative holder's stage. Behind was another bellows connecting it to the light source. Theatrical gels that matched Polycontrast filters could be slid in a slot in front of the light source. Light source was huge, most certainly made of multi tungsten bulbs with a very efficient cooling system that exited the cooling air outside the building. Do remember test strips were 8x10 sheets of paper. Full sheets were processed in one very large tray with chemical dumped in and drained out. FYI: Chemistry was supplied for free from Kodak. Roll of paper probably also donated by Kodak. Back then in Kodak's heyday, they donated huge amounts of materials to RIT. Now for the all important fact.... size of the enlarger. Unfortunately can't remember but it was a square format and probably between 24" and 36".

  4. #24
    Eric Woodbury
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    Re: 20х24" enlarger

    You probably know all this stuff if you are tackling such a big project, but let me write it down anyway.

    I'd guess your light source, at full power, to be approx. 600 to 1000W. Keep up to date on the latest LEDs. More efficient products every day. Drive the LEDs with current sources, not voltage, as LEDs have steady light output with current. Source needs to be oversized and the size would depend on the enlarging lens angle. Edges are horribly uneven. Also, remember no such thing as a perfect diffusor. Perfect is no loss and everywhere even. Won't happen. Therefore, we can infer from this that since it is not a perfect diffusor, that some image-able light comes through. Furthermore, as the lens is stopped down, there will be more focus on that image of the light source which appears as unevenness. Thus, design the light source as even as possible, as if there were no diffusor, and make it oversized.

    I wonder if it is possible to make a vacuum neg carrier that is the diffusor, too? I don't know how to do this, but if it were possible, then one could 'suck' the neg up against a plexiglass surface. (BTW, there is a new plastic diffusion material that uses air bubbles instead of white for diffusion. It is suppose to be more diffuse and efficient. I have some, but haven't tried it yet.) The advantage here, besides the flatness, is that no Newton rings are formed with a neg in direct contact with a diffused surface. Plus, any dirt on the mating surfaces virtually disappears. Another trick I've seen for holding 8x10 negs flat is to have an aluminum frame to which the neg is held flat with simple clamps at the edge. Once inside the enlarger, the heat expands the aluminum more than the negative and pulls it tight. Not sure that this would work with sufficient flatness for 20x24. Depends on the temperature coefficients of expansion for both materials, but this can be calculated.

    A wide-angle enlarging lens brings "cosine to the fourth" errors. Impossible to correct without the attenuation of another filter. And as noted above, the light source would have to be extended even more to accommodate the lens (since the light source can be 'seen' through the diffusor).

    Lots of advantages to horizontal since gravity works in your favor. I can see while reviewing this that the neg carrier could be heavy. It would be good to calculate its weight early and consider how the neg is installed and moved into position. Might be easier to clamp opposing edges that hold the neg in tension with springs or weights. The business with the laser alignment seems a bit of overkill, but I have never designed with such things. How about a vertical neg and horizontal paper with a reflex? Too weird. How about a air-floated optical bench for the whole thing? Might be able to find one used.

    Hope this helps. Disregard after reading. --ew--

  5. #25

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    Re: 20х24" enlarger

    IMHO, having a huge enlarger for something like a 20" X 24" neg sounds cool, but if the print will only be 20 X 24 (1:1) it's a lot of work/big commitment to build the beast in the first place... (WH Jackson did OK with those large contact prints...) Maybe work on bigger cameras for bigger negs that can be contact printed would be OK...

    When I worked on large scale murals that were to be "tiled", it is MUCH harder to match many prints so the final effect is even looking, so I have no problem with inkjets for multi-print murals, because if there's a mounting issue, making another print is no problem, but with traditional processes, sometimes just another day in the darkroom produces different results for critical matches... And there's the issue that the choices of large roll paper are shrinking, so there might not be a long term opportunity to use this beast...

    Another possibility for light stage coverage is the use of a large fresnel (+ diffuser?) near the negative, with the lamp farther away at the focal point... These can be had from old large screen projection TV's, and can be surprisingly even if set-up very carefully... (I sometimes use one for a "daylight" light source studio effect using a small lamp at a distance...)

    Good luck,

    Steve K

  6. #26
    mamanton's Avatar
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    Re: 20х24" enlarger

    In my opinion, mostly the Camera 20x24'' will be used for shooting portrets with an old lenses. And unsharp areas somewhere on the background is ok ))
    But, probably, we'll make some landscapes too. We'll see... In any way it's a custom made enlarger, which we may renovate or upgrade later on.
    Of course, we are trying to create a perfect design of the enlarger - that's why I'm writing here.
    Thanks everybody for your interest and advises!!!

    Quote Originally Posted by Drew Wiley View Post
    Those of us who routinely yet precisely enlarge 8x10 film know that the straw that breaks the camel's back is likely to either be depth of field compromises or
    imperfect film flatness at the time of the shot. While the latter can be controlled, and the former by judicious composition selection, going clear up to 20x24 film means that very little in the shot will be truly in focus. The "circle of confusion" becomes a playground of confusion, depending on the degree of enlargement, unless you're talking about flat copy reproduction using vac film positioning. ... Not that this route hasn't been tried before, and that one man's cul de sac is another man's engineering dream vacation to Disneyland. Good luck, and have fun regardless!

  7. #27
    mamanton's Avatar
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    Re: 20х24" enlarger

    Quote Originally Posted by Randy Moe View Post
    Everything is compromise.
    I should not have assumed from your location.
    I only meant anything is possible.
    Yes, I understood. It was a joke ))
    For sure, in every country you can create something special and amazing! Everything is possible and depends on people!

  8. #28
    mamanton's Avatar
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    Re: 20х24" enlarger

    Quote Originally Posted by Greg View Post
    I graduated from The Rochester Institute of Technology in 1973. Saw a lot of very unique photographic equipment while I was up there. In one room was a really large horizontal enlarger. From what I can remember everything ran on two floor tracks. "Easel" had a box on top that held a roll of Polycontrast paper. There was a light trap from which the paper was rolled down from. Typical lens stage with bellows connecting it to the negative holder's stage. Behind was another bellows connecting it to the light source. Theatrical gels that matched Polycontrast filters could be slid in a slot in front of the light source. Light source was huge, most certainly made of multi tungsten bulbs with a very efficient cooling system that exited the cooling air outside the building. Do remember test strips were 8x10 sheets of paper. Full sheets were processed in one very large tray with chemical dumped in and drained out. FYI: Chemistry was supplied for free from Kodak. Roll of paper probably also donated by Kodak. Back then in Kodak's heyday, they donated huge amounts of materials to RIT. Now for the all important fact.... size of the enlarger. Unfortunately can't remember but it was a square format and probably between 24" and 36".
    Golden times!

  9. #29

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    Re: 20х24" enlarger

    Concerning the movement of cooling-air affecting the neg, is it not possible to use the diffuser as a 'wall' between the LED- array and the neg? Or is there some technical requirement to have the LEDs and the neg in the same airspace?

    I suppose a neg carrier would most simply be based on tension, by means of edge-clamps and parallelograms in the same plane as the neg. The corner springs used in some carriers for 4x5" and 8x10" would be impractical for anything larger (if they ever worked anyway). The question becomes whether sufficient tension can be applied to remove sagging (the tension frame would help with rigidity of course) without destroying the neg, or stretching it.

    Negative material is available in this size as a special order, so that might not be a problem. Is paper available in a size that would make the prints worthwhile and able to recover the cost of enlarger production? Looking on manufacturers websites, large paper sizes approach that of the coating machines - for example, 56" roll seems to be the largest from Ilfordphoto, implying a print of roughly 56"x 67", hence a linear magnification of just under three, without cropping.

    Presumably the machine will be a for-hire system (hence the rails-free design), moved around for different projects like the huge old Polaroid cameras or the big, walk-in cameras with Harman Direct-Positive paper -- in turn that implies providing a 20x24" camera to produce the negatives.

    Good luck with such an interesting project.

    Edit: Might a light-source using studio-flash into a diffuser-box remove cooling, cost and complexity problems tied up with the LED head? Two exposures, or two flash units, would provide the light for variable-contrast papers but dodging and burning might be tricky!

  10. #30
    bob carnie's Avatar
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    Re: 20х24" enlarger

    I agree with Drew

    For what the OP is trying to do I would think about a dream enlarger PIPE DREAM

    this is how I see such a setup working, now I know the OP has particular needs but I am being greedy here and designing one for myself.

    Overhead rail system with stepper motors on the back and forth for the unit as well back and forth remote control of the fine focus, This most likely would require a Durst Style Negative stage, but biggie size.
    The lens would be of the finest quality and speed.
    The lightbox / power light unit has already been designed (Lisle Camera) so I know this works.
    Creating Magnification Charts is easy if you are so inclined for changing paper.

    The wall would be adjustable with a very good vacumn system and within the room everything would be painted black, of course a econoroll for paper delivery and cut.

    We have tried to have paper dispensers on the vacumn walls in the darkroom, I never saw one that worked to my needs, placing magnets for positioning and kicking on the vacuum when paper is in place is very easy.. On a very good day at Jones and Morris Photo Enlarging I could put 5 boxes of paper on the wall - that is a lot of paper.


    2 times magnification is 40 x48 - three times takes us out of the realm of commercial made paper.

    For me the problem would be the Camera Stage , being able to get a good technical negative not to mention something I would like to print.

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