Power the LED by a small flyback converter. The current limiting resistor can eat a lot of power. Note, this schematic is only an illustration. Some design/programming work have to be done.
Something like this:
simulate this circuit – Schematic created using CircuitLab
Here is a simple model (for LTSpice IV) of the above schematic. It demonstrated efficiency of 95% and higher:
Version 4
SHEET 1 880 680
WIRE 256 -160 -288 -160
WIRE 544 -160 256 -160
WIRE 256 -32 256 -160
WIRE 544 -16 544 -160
WIRE -288 96 -288 -160
WIRE 256 128 256 48
WIRE 544 128 544 48
WIRE 544 128 256 128
WIRE 256 176 256 128
WIRE 208 256 -48 256
WIRE -48 304 -48 256
WIRE -288 416 -288 176
WIRE 256 416 256 272
WIRE -48 432 -48 384
FLAG -288 416 0
FLAG 256 416 0
FLAG -48 432 0
SYMBOL nmos 208 176 R0
SYMATTR InstName M1
SYMATTR Value IRLML2803
SYMBOL ind 240 -48 R0
SYMATTR InstName L1
SYMATTR Value 100µ
SYMATTR SpiceLine Rser=1
SYMBOL LED 560 48 R180
WINDOW 0 24 64 Left 2
WINDOW 3 24 0 Left 2
SYMATTR InstName D1
SYMATTR Value NSSW008CT-P1
SYMBOL voltage -288 80 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value 5V
SYMBOL voltage -48 288 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value PULSE(0 4 0 10n 10n 3u 50u)
TEXT -322 456 Left 2 !.tran 1m
As poster states,
A very bright RED LED lamp (~50W) with a lamp tripod or something
would be perfect for me.
Given the fact that one can easily buy off-the-shelf, 50 to 150w, LED flood lamp, with heat sink and drive electronics, but they typically comes with white LED.
One may consider simply replacing the central coin sized LED module and make corresponding small change in drive V and A.
Either do it yourself or if, in (small) batch quantity, manufacturer can do it for you.
For example, I am using this 10W LED, which is 9 LED die, 3 series in one set and 3 set in parallel. It is 350mA, 10V. The constant current driver board is adjustable up to max. 5A.
The RED LED module shown (which I do not have on hands, but, same principle as the 10W I have) is 10 LED by 10 LED, each die is one 1W LED, module is about 32V and 3.5A.
The example spec. is white LED (which is actually blue then changed to white) and voltage is slightly different from red but is same range 3.x to 4.x V
Commercial 100W driver with CE, 85 to 250V AC in, out DC 20 to 38V, 3A
Best Answer
Maximising brightness:
Brightness is a function of amount of light and area illuminated.
More light = more brightness.
Less area = more brightness.
So
For more light obtain as many lumens as you can afford.
For less illuminated area use LEDs with low "radiation angle" or "cone angle".
Lenses:
If that is not bright enough you can use a lens or reflector.
Many companies provide lenses for LEDs.
Deal Extreme have a range here
Effect of colour: Note also that brightness is related to eye response to colour - yukky yellow green is about the best colour for optimum eye perceived brightness - but if you want a specific colour this is not much help in optimising brightness.
Related: Mind plasticity add on for the ever young:
Lime Green is close - Lime Green Fire Engine from here - BUT more recent studies suggest that familiarity is more important than visibility for emergency vehicles.