DIY 8x10 (or larger) Enlarger Chassis

[Drew Wiley]

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.

[Ethan]

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_/

[Ethan]

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




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.

[Ethan]

Here's a long overdue update on the DIY 8x10 LED enlarger project. It's finally coming together in real life (outside of CAD, sketches, and schematics), and it's very satisfying to see its physical form come together, and surprisingly work the way I intended with only a few issues. One issue I've come across, which won't be very big in actual use, but bugs me since I don't know what is causing it is that on low brightness (less than 10%) the LEDs don't turn off instantly and instead take about 1/2 a second to fade. I'm going to reach out to the DMX decoder manufacturer and see if they have any ideas, because I'm pretty sure the issue is somewhere in that module. Luckily changing Brightness from maximum will only be needed when color printing, and I doubt anyone would ever need to cut one of the channels by 90% to get the correct color balance.

Anyway, here's a video explaining how it works in it's current form:

[Tin Can]

Please carry ON!

[John Layton]

hmmm...incorporate a Sinar electronic shutter as a work around to the fading issue?

[Ethan]

hmmm...incorporate a Sinar electronic shutter as a work around to the fading issue?

I have an electronic packard shutter I can add if I need to, but I think the solution will just be to disable brightness less than 10%. I can’t envision any scenario where that much filtration would be needed. I haven’t done any color darkroom printing, but on even the worst negatives do you ever need to cut 90% of one channel? I don’t think dichroic heads can even go that far.

[Ethan]

I talked with the company which made the DMX decoder, and I was able to find a solution to the fading, so now all values can be used accurately for printing

[Ethan]

I now have all the enlarger pieces, and will be building it over the next week. The last parts which arrived today were the sheet metal pieces, which I ordered from a company in Reno called SendCutSend. I think they're fairly new in the prototyping industry, but I am seriously impressed with their work. The reason I went with them is that they were at least 50% cheaper than the other more established companies like protolabs. There was a delay in the manufacturing of my parts (apparently one of the pieces didn't pass quality control and had to be re made), and when I reached out to them about the delay they were quick to respond and gave me a 15% discount on my next order. That was nice I thought, but then, even though I selected the free shipping option, they overnighted all the parts to me (from Nevada to Massachusetts) so they still arrived the day the initial estimate said, which I'm sure wasn't cheap, give its probably 50 pounds of aluminum in weird sizes. Overall a great experience (and I swear they're not paying me to say that :-P)

[Tin Can]

Gotta love people who are AII in.

Both you and the supplier