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Thread: DIY 8x10 (or larger) Enlarger Chassis

  1. #71
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    16,006

    Re: DIY 8x10 (or larger) Enlarger Chassis

    What happens when the LED technology shifts or advances enough to make obsolete your chosen LED components? It's inevitable. You better have your own set of spares. And hopefully you are trying to devise something for sake of VC papers, not actual color printing. Being somewhat off in the green is going to especially limit hue accuracy, since that the primary our own eyes are most sensitive to. But I'm skeptical in general about the accuracy of LED's in color printing at this stage of the game, while tried and true halogen colorhead options are so readily available. But good luck to you. Not every pioneer made it through the wilderness; but some did.

  2. #72

    Join Date
    Jun 2019
    Location
    Western Massachusetts, USA
    Posts
    264

    Re: DIY 8x10 (or larger) Enlarger Chassis

    Quote Originally Posted by Drew Wiley View Post
    What happens when the LED technology shifts or advances enough to make obsolete your chosen LED components? It's inevitable. You better have your own set of spares. And hopefully you are trying to devise something for sake of VC papers, not actual color printing. Being somewhat off in the green is going to especially limit hue accuracy, since that the primary our own eyes are most sensitive to. But I'm skeptical in general about the accuracy of LED's in color printing at this stage of the game, while tried and true halogen colorhead options are so readily available. But good luck to you. Not every pioneer made it through the wilderness; but some did.
    I'm only planning on doing VC printing myself, but in theory it should work for color as well. Remember that the green hue created by a color head and RA-4 paper is not determined by the frequency of the green light, but the amount of light it is exposed for. RA-4 paper only has 3 colors in it, so the hue will be the same, as long as the exposure is adjusted accordingly. If you look at the Fuji Crystal Archive paper data sheet linked below, the magenta dye curve (which is the one effected by green light) in figure 12 has a density peak around 550nm, and the curve is heavier on the lower end, so 535nm should work fine I think.

    https://asset.fujifilm.com/www/us/files/2020-02/9251484a0eda6ebb4b47cc6fec73173a/Fujicolor_Crystal_Archive_Type-CA-Data-Specs.pdf


    Also, Heiland has had success printing with LED heads, and though I don't know specifically what LEDs they use, but from my research I could not find any narrow band green LEDs with a peak at 550nm. This is their most recent post on instagram:

    https://www.instagram.com/p/CTwmRM9IQh_/

  3. #73

    Join Date
    Jun 2019
    Location
    Western Massachusetts, USA
    Posts
    264

    Re: DIY 8x10 (or larger) Enlarger Chassis

    Hey folks. I've got another update here on my DIY 8x10 Enlarger.

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    I haven't changed any of the design since last time, but I am working on an addition to it, the addition being an ultraviolet lightsource for enlarging alt process prints.
    You may be thinking "This man is crazy! It can't be done!"

    well, if you had asked me a few months ago, I would have agreed with you, but since then I've seen things...

    To be precise I was showed a thread on Photrio where a couple people have built successful UV enlargers. The guy responsible for the basic design is a fellow from the Netherlands named Douwe, who has been experimenting with UV enlarger designs for the past couple months.

    The primary issue most people run into with UV enlarging is that modern lenses have coatings which block UV light, making them useless for this. Most uncoated lenses work better, but still not great. The current hypothesis for why this is, is that most cements used to fuse lens elements also block UV light. Dialyte lenses (air spaced lenses with no groups) seem to be the most transparent to UV light, giving credit to this theory. The best lenses I've heard about are the Kodak Enlarging Ektars and Enlarging Ektanons from the 1950s, some of which are uncoated dialytes. With them, Douwe has been able to achieve 20 minute cyanotype enlargements from a 40 watt medium format UV enlarger.

    Another issue is that UV bulbs tend to put out a lot of heat. So much so, that one guy who made a diffusion UV enlarger was seeing his negatives start melting after ~10 minutes. The solution is to use condensers instead of diffusion, which is now possible thanks to small, high power UV LEDs. Diffusion enlargers work fine when you can put a couple hundred watts of light into them, and for visible light that's fine, but even a couple hundred watts of UV LED light can still put out too much heat. Condensers allow for much more efficient use of light, which in turn means that far less light is needed. For his enlarger, Douwe only used a 40 watt LED chip.
    For my 8x10 I'm going to use a 300 watt LED, but with a big enough heat sink and enough air flow around it I think I should be able to manage the heat. I'll also be spreading it over a larger area.

    The design in the renderings I've posted is my mock up of what I think will work for enlarging 8x10 negatives using UV light. Its fairly tall to accommodate the condenser fresnels (not full lenses, they would be too expensive and too heavy), and a bit ugly at the moment, but I may try to make it look a bit nicer before building it.

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