3x1.5V use a Diode instead of resistor????

I've been wondering for about a week now, if I were going to do a crude 3 cell flashlight conversion, why not use a 1AMP or great silicon rectifier diode in series vs a resistor? I estimate a fresh set of alkaine at 1.55Vx3 or 4.65V, a silicon diode should get me down around 3.95V with fresh batteries... What say you engineers? Sure, I could use some circuit... I'll eventually use a LM317A in some creation, but for fast 'n easy... Why not just a FWD bieased diode?

No problem using a diode rather than a resistor. You will have a rather constant 0.7 V drop. The nice thing about using a resistor is when your batteries run down and the current falls off, the resistor will drop less voltage. Either way keep your power in mind. The power dissipated in the resistor or diode is the current times the voltage across the device. So for the diode, it is your operating (led) current times 0.7. More than about 1/2 watt gets pretty hot.

~1/3W {consumed in diode} then in a 1W Lux conversion I'm guess... .4A * .7V and round... I may try both with already-low batteries and see how it behaves. In a lantern maybe one could use a tiny relay coil in series... and as current falls relay lets go and you fall into wide-open mode on low bats [relay bypassing it's own coil]. That's just a brain-fart. Could be done solid-state somehow too, eh? V at LS/Diode junction or resistor/LS jucnction could control something that pinches off alternative path normally, and creates alternative path when batteries are tired. Or a bypass SW for resistor, eh?