Interesting! I have used plenty of LM317s with LEDs, but I never thought of using them to regulate brightness - I would just pick whichever resistor corresponde

Interesting! I have used plenty of LM317s with LEDs, but I never thought of using them to regulate brightness - I would just pick whichever resistor corresponded to the forward current specified in the emitter datasheet. Didn't realize that there was enough room on the curve to use current control as a meaningfully configurable brightness setting.