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By Inventabuild
Please let me know which led's you recommend for lighting up lithophanes 3x4 IN and larger with the following requirements:

1. Run on batteries (up to D size?)
2. Will last at least 6 months if left on continuously

Thank you.
By lyndon
I took a printmaking class several years ago, including intaglio, but I had never heard of a lithophane, before now!

That said, I don't think any particular LED will matter, the issue you're going to run into is diffusing the light across the entire scene. Modern LEDs are very efficient but you're not going to get 6 months of continuous usage without a lot of batteries. Say you had one LED drawing 15mA, and that was powered by 3 D cells. The first google hit for D cell capacity gives 13000mAH, which is 867 hours or 31 days at 15mA. If it was only on for 8 hours a day you'd be up to 90 days. And that's for only a single LED, which is likely not enough unless in a dark room. My guess is that for a small 3x4" image, 4 LEDs with a diffuser would be enough.

Your first order of business would be to decide how many LEDs needed for the amount of light you want, then go from there.