light 101

It is not easy to give a single answer to any of you questions. I can try to say something about you question, but it is not a full answer, only a popular explanation:

1) Any light emitter send out some light (lumen), how far it will throw is depend on how focussed it is (Lux). To compare light from different types of light sources you look at lumen/watt specification. See here for some numbers: http://en.wikipedia.org/wiki/Luminous_efficacy

2) A led will surpass a old incad very easily, at least in brightness, but not in color rendition.

3) Batteries do get better, but in led lights the electronic also has a huge impact on how the light works, especially on single cell lights (1.5 volt), where there are large differences between different brands of lights.

If you want to compare a whole gaggle of newer type lights, both HID and LED, against your ol' Maglite D-cell, http://fonarevka.ru/indexen.html always brings along a large Maglite 6D incandescent so one can compare. oo:

Lumen is the unit for total amount of light emitted from a light source. The SI unit candela (commonly called candlepower) is the total amount of light emitted in one direction. Lux is the amount of lumens in a single determined area.

The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian.

Click to expand...

1lm = cd·sr

1 lx = 1 lm/m2 = 1 cd·sr·m–2
http://en.wikipedia.org/wiki/Template:SI_light_units

I guess that might be comparable to Ohm's Law and the interrelation between volts, amps, ohms, and watts. Obviously it doesn't correlate completely.

http://batteryuniversity.com/learn/ is an excellent resource for the most popular high performance battery type today, rechargeable lithium-ions. There's primarily two types in use amongst flashlight enthusiasts, lithium cobalt for higher energy density, and lithium manganese for higher current tolerance and higher safety. There's more details to be found around the forum. The other common type is low self-discharge (LSD) nickel metal hydride batteries like Sanyo Eneloop brand batteries. I don't know much about them at all but lots of people swear by them.

You can also find plenty of nitty gritty discussion on battery technology right here at CPF, in the Flashlight Electronics - Batteries Included sub-forum.