Potentially useful LEDs for darkroom/alt applications

[koraks]

Yeah, there's many challenges Tin Can, I know. Before you know it you'll be going through a crash course of electrical engineering instead of making images. 'Luckily' for me electronics has always been a hobby for me so it's trying to find synergies between one hobby and another.

To make matters worse than the list of issues you mentioned there's also the topic of optics. It's not addressed much save for an odd thread here and there on Photrio. With LED you've basically got two choices, as with any other light source: diffuse or (quasi-)point source. They're both challenging if you try to implement them with LED. If you make a diffuse light source and you want any kind of significant light output also for bigger enlargements, there's the issue of heat dissipation. You'll be handling a fairly big box or plate with many high-power LEDs and you'll have to somehow get rid of the 100+ Watts (or in case of my latest contraption 360W) of heat in a way that doesn't interfere too much with...well, anything. Not to mention getting really even light output across your color channels. Going for a point source/condensor setup is even trickier since a single LED is just about a perfect point source...but you never have just a single LED. Try to take the light from an array of dozens or hundreds of point sources and somehow coax them into behaving like a single apparent point source. Sure, it could be done, but you may add optics design and with any bit of luck lens manufacturing to your list of newly acquired hobbies.

I hope to pick up actual printing again in a few months when we have moved and I'm done renovating our new place. Between posing as an electrician, plumber, carpenter, ensuring that there's food on the table and also attempting to keeping my violin practice up a bit, there's just no time to spend on photography at the moment. Not to mention I really want/need to engineer my new darkroom work/safe/evaluation light system...

[Tin Can]

LED evolution, they are getting better fast

I have printed up 30X40 from 8X10 film with simple LED panel with LED diffusion plastic

I had to reduce power to 10% as my panel was way too bright

Not perfect, an experiment, 8 years ago and posted here in DIY

I have been experimenting with electricity since a young child

KD0IJD

Perfection is the enemy of progress

[koraks]

Lucky you. My first LED color head had around 100W net power. This was insufficient to conveniently print on warm tone paper from 35mm negatives onto sizes of 11x14". I like to keep exposures between 6 and 20 seconds, roughly. No problem with color, from any size negative from 35mm up to 4x5", and neutral tone B&W paper was also perfectly fine. But warm tone and especially lith prints were too slow to my taste. The new 360W head is about 2 stops faster, although I haven't printed much with it yet. 5x7 RA4 prints from 35mm color negatives are now 2-5 seconds at f/22 or thereabouts. I have a feeling this head is fast enough to handle all my printing needs.
It doesn't help of course if you design a head for color printing that you 'waste' most of the power on the red channel - which is a waste only when printing B&W of course.