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Thread: DIY 8x10 (or larger) Enlarger Chassis

  1. #31

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Here's the finished chassis design. It's looking like the chassis will cost $1900 to build, which is a bit more than I had been hoping for, so I might fiddle around with it some more and see if I can knock the price down on some things. It looks very reflective in the renderings, but the real extrusion is fairly dull, and I'll paint everything inside the bellows area black. Might also get some sheet metal shrouds made for it at some point after it's built, but that's an idea for later down the road.
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  2. #32
    ic-racer's Avatar
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Quote Originally Posted by Ethan View Post
    It's looking like the chassis will cost $1900 to build,
    About five times less than a KIENZLE. You can undercut the competition with a good profit margin if you want to sell some of them.

  3. #33

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Quote Originally Posted by ic-racer View Post
    About five times less than a KIENZLE. You can undercut the competition with a good profit margin if you want to sell some of them.
    Hah! though somewhat true I suppose, my main passion is shooting the photographs, not making the equipment. I do enjoy designing and building things, but after a few of the same it starts to get boring. That price estimate is also only for parts, and it will probably take a fair amount of labor to assemble it.

  4. #34

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    In working on the timer, I spent today figuring out the math behind f-stop printing. I compiled my equations in a Desmos (online graphing calculator) graph, which you can look at here:

    https://www.desmos.com/calculator/zltt8ccfik


    The way I laid it out, you start in a test strip mode where you set your base exposure, size of each increment (ranging from 1/12 of a stop to 1 stop), and then the number of increments you want. You then start the test strip, where for each time you expose, it will change the time accordingly with the size of a stop you selected. After processing the test strip, you input the number of stops needed for the best exposure, and it will calculate the total time based on that. I plan on having a memory function as well, where it will remember several exposures so that I don't have to recalculate when I change filters for split filter, and I'll also be able to input the stops at at the start if I've already calculated the exposure for that print.

  5. #35
    Drew Wiley
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    block-style T-slot extrusions can get expensive, though I have a certain amount on hand I got for free, useful for misc props and jigs. But its metric, so not compatible with most US dimensional product. If contemplated it myself for neg carrier applications, but found a more space-saving alternative even more precisely aligned .... long story. Sometimes I do get that shop itch. People across the street work on a speed boat every weekend. Another neighbor tries to restore classic cars. Others like fooling with vintage motorcycles. Why not enlargers? There's a certain amount of satisfaction in making one which not only works well, but looks good too.

    ... was just reminded why I went with wood structural beam material instead of metal .... a nice one two minutes ago, about 3.0 on the Richter scale. Whole house swayed. No damage. But we get significantly bigger ones sometimes.

  6. #36

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    lol, I'm famous!


  7. #37

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    I'm working on writing the code for the color controller. I want to have two modes for CMY and RGB color, because RGB is more useful for black and white in my opinion, but CMY is the more traditional printing scale. The issue I'm running into though, is that I don't know how to convert them. the RGB values LEDs can understand go from 0 - 255, and the traditional enlarger CMY scale goes from 0 - 200. However, digital CMY which is all I can find conversion charts for, goes from 0 - 1, or 0% - 100%. Do any of you know how the 0 - 200 darkroom printing CMY scale converts to the digital one used by photoshop, etc?

  8. #38

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    So... more thoughts on the info from my last post.

    I've learned that there's no simple conversion, since color filters don't apply evenly or linearly to the light source, and the (usually tungsten) light source itself isn't uniform either.

    The way to program a conversion then, is to take a bunch of color readings of a dichroic head, and calibrate the LED head until they match. For this I'll need a color meter, which I don't currently have. I can get an older minolta one on eBay for an amount I think is reasonable, but the newer ones cost too much.

    Here is my current issue / maybe not an issue. Old color meters only read red, green, and blue light, and assume the light source is full spectrum, meaning that the light is roughly even across all frequencies. LED lights do not emit full spectrum light, they have peaks and low points in the color of light they emit. Because of this, most people say not to use old color meters, and that a modern one which takes into account those dips and peaks is needed. When I read this I was disappointed, because I'm not about to spend $1600 on a color meter I only need for one project.

    However, I thought about it some more, and now I'm wondering, is the limited sensitivity of old color meters even an issue? Multigrade black and white papers are only sensitive to blue and green light, and RA4 papers only to blue, green, and red... so if the color meter can only read blue, green, and red light, would the measurements still be fine for calibrating the enlarger head for paper?

  9. #39

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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Very cool, Ethan.

    Quote Originally Posted by Ethan View Post
    Here's the finished chassis design. It's looking like the chassis will cost $1900 to build, which is a bit more than I had been hoping for, so I might fiddle around with it some more and see if I can knock the price down on some things. It looks very reflective in the renderings, but the real extrusion is fairly dull, and I'll paint everything inside the bellows area black. Might also get some sheet metal shrouds made for it at some point after it's built, but that's an idea for later down the road.
    Click image for larger version. 

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  10. #40
    Tin Can's Avatar
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    Re: DIY 8x10 (or larger) Enlarger Chassis

    Here is a reference, a $20,000 FOTAR 10X10 made very much like a DeVere but bigger. 8ft column, no safeties, no head, no film carriers.

    It has a very difficult cable/capstan system with lots of HEAVY balance weights

    I used it for a few years with several DIY heads

    In the picture I have 5X7 Saltsman glassless film carrier, LED head. I think the table was 32X40"

    Sold it 4 years ago for a profit, when I bought it, the big photo store was asking $250 on eBay, they disassembled, loaded into my pickup, the young man almost lost his hand, when he tried to stop a heavy weight by wrapping the cable in his bare hand. My buddy and I were not allowed to touch it, until the hand...owners orders, aka insurance fear

    When all was balanced the 2 hand wheels moved it by fingertip, and the same single finger could lock it tight, very smooth

    To do that I had to replace the nonexistent old head with 30 lb barbell

    FOTAR by TIN CAN COLLEGE, on Flickr
    image

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