I used plug-and-play strip LEDS from Superbrightleds with one of their pulse width modulator dimmers (also plug and play for dummies). Very cheap. These particular reds peak at 626nm. Obviously there is an emission spectrum around that but I didn't do a CD-type test because I knew I was going to use them behind a Kodak #1/#2 safelight filter anyway as this project was initially strictly intended to be a super-safe DIY safelight for ortho films. But I ended up expanding the project (documented somewhere on here) to a "mark II" version in which the board with the red LEDS could be swapped out for one with warm-white LEDS (same type of strips from Superbrightleds) and then the red safelight filter is swapped for an OC which I use for paper. Fun little project. I tested safe times out to 30 minutes with a few materials (way longer than I'd need) and stopped there. Didn't bother going longer but it might be fun one day to see how long. For people with more soldering/wiring skills Superbright sells component LEDS that peak at 660nm, which is obviously preferable.