Bright-brighter-brightest
 

I am confused about the various bulb applications regarding flashlights and bike headlights using standard batteries.
If you take a two cell DD flashlight and swapped out the bulb which would be the brightest? Incandescent--Krypton--led or halogen.
I want to upgrade the bulb in my vintage headlight. There are krypton bulbs with screw bases which would make life easier than a socket conversion. I wonder if they are any brighter than the standard PR2 bulb? Any ideas?

For this application, I doubt that there would be a noticeable difference. Any 3 volt light is going to be very weak. I don't think you can even get a LED conversion for screw-in base and the plug-in base ones aren't really anything to write home about.

3-volts severely limits what you can do. It's probably best to just keep your vintage light just as it is. An LED conversion is a possibility but the reflector in your light is not going to provide a good pattern so your not going to be happy with that. High Power LED's require heat sinks and that complicates the conversion as well. It's best to build from scratch. Here is a good site with lots of information on building very good lights for your bike.
http://pilom.com/BicycleElectronics/...lectronics.htm

Here is a good place to obtain high power LED's and optics.
http://www.dealextreme.com/

There are LED modules made by Terralux that are 50 lumens. The standard 2D bulb is more like 15-30 lumens, so it's a decent upgrade. 50 lumens may well be insufficient for night riding by itself w/o background lighting, but anyway it's a decent start.

Warning: make sure you get the polarity right, as getting the polarity backwards could fry the quite expensive LED. Most LED modules are pos at the tip of the base, and neg on the surrounding body.

I hate to say this but that bulb will produce less light than the filament bulb you would be replacing it with due to the change in pattern with the original reflector. The beam will be excessively wide wasting most of the light where you don't need it. The only advantage with the LED replacement bulbs are long life and extended run time with batteries. Granted, there are advantages to long run times and a bulb that lasts 50,000 hours but they simply will not produce enough usable light with reflectors designed to be used with filament bulbs to actually see where your going. The Cree XR-E Q5 high power emitter produces 228 lumen coupled with a good optic designed for that emitter will produce more light than an MR-16 20-watt halogen bulb and only consume 3 watts.

At nominal voltage...maybe. The MR-16 puts out 800 lumens at 12 V...which is a bucket load. That's gonna have to be soooome optics;)

I agree with everything else, however.

They are! Optics are keeping pace with emitters. Note this graph for the latest 6X15 elliptical lens and holder.
http://www.quickar.com//25x6.gif

No wasted light illuminating areas that don't need it and concentrating it where you do.
http://www.quickar.com/imsheader.jpg

So they are getting to about the point that the MR bulbs are at now?;)

n4zou - I agree that optics are getting better. But the bottom picture you attached is comparing optics to reflectors. Are reflectors better than optics? Looks like it to me.

It's a combination of both reflectors and optics. Half the reflector is actually a part of the LED and the other half of the reflector is located in the holder that attaches the optic to the LED board. Unlike bulbs, which have a filament elevated above it's single reflector LED's are placed between a reflector and it’s clear plastic cover, which also acts as a lens. Optics for LED's are multi lens and reflector systems. 3mm and 5mm LED's contain both reflector and lens molded around the emitter element producing a generic flashlight type beam. High Power LED's are used in various applications and this simple generic beam pattern is not adequate for the various applications there are being used in and heat sinking is not possible allowing high power operation. Take your automobile headlight for instance. The beam produced is elliptical and not simply round like flashlights and MR-16 landscape lights. Combining separate reflectors and optic elements into a single optimized package for a tailor-made light system gives the user the most light for the intended purpose at reduced power requirements.

Yes, and only using 3 or 5 watts in the process. You can operate a 5-watt LED light producing as much or more light when using custom optics 4 times longer with the same battery than a 20 watt MR-16 bulb.