Testing two LED bulbs , the top one ( pictured ) will be Number one and the one bellow will be number two .  I have been playing with LED bulbs for quite a few years , not quite sure when I first built one myself ( must be half a decade ago ) . I took a SSC P4 emitter and soldered it to a screw ( the head ) and gutted a incandescent bulb .. Drilled it out to feed the screw out the bottom and soldered one of the tabs to the side of the body of the bulb and there you had it , a SSC P4 bulb .  ( I still have it )

 Ever since doing that mod I have been waiting for the manufacturers to catch up with some cheap offerings , and here we are .   

 Lets start with the top one shall we .  

 In my very old ( possibly first flashlight ) from the 1970's 3D incan . The first LED bulb pulls some 0.33 amp and I think that is simply too much . The light started out a very slightly purple tint and after a minute was turning a blue tint . This bulb is being advertised as 3v to 18v , but I think 4.5v is pushing it hard . I put the bulb into a 2D flashlight and the current dropped to 0.01 Amp and it seem to run very happily . Though I would call the light output Moon mode the run time at 0.01 amp should be amazing .  @ 4.5v I really did like the amount of light that was produced as well the beam profile , very XR-E Thrower but I just don't see it handling the voltage for any length of time .

 Bulb two ...  I put it into my old incan and immediately liked it , the light was more yellow than purple , has a nice XR-E style beam , but with a current draw of about 0.06 amp ( oh yeah , 0.06 amp ) that's 60 mAh in a 3D flashlight ..  Reminds me of a good 1970's 2D incan for power output .  I really like this bulb , low current draw and just enough light to be useful .  ( This bulb could be something in a 4D or maybe even a 6D if it handles the voltage ) . I am leaving this bulb in my vintage 3D until perhaps something better comes along . I really like the beam profile with both these bulbs .

 What I wanted was very low current draw , decent tint , a good beam profile and a useful amount of light . For that vintage incan , these bulbs just might be the way to go , but if you are after real light and I am talking about a mini sun you keep in your pocket , then it has to be XM-L or XP-L .  

 First bulb - 2D Vintage light - 0.01 amp - 6 Lumens ( Measured )

 Second Bulb - 3D Vintage light - 0.06 amp - 25 Lumens ( Measured )  I expect the output to be higher as the head does not fit my light box . So a very iffy measurement for lumens .

 I am not going to do the other bulb ( one )  in the 3D because every time I replace the bulb it just gets harder to get the light to work , and it took me 15 minutes to get the light to work after messing about with bulb two ... Just too old a light to be messing with , but it seems to be working reliably now ...