This is the PALight's output on the low setting, photographed with a 1/5th second exposure...

...and this is the high-setting output, at 1/20th. It's easily up there with the output from the tight-beam Dorcy lights, but the PALight's much more compact.

Compared with pretty much any incandescent-bulb flashlight, the PALight is still pretty dim. But it's genuinely pocket-sized, the always-on feature is really handy for anybody who reckons they're likely to have to find their flashlight in the dark, and the Survival model's extra features are useful. And the thing's really very reasonably priced.

The PALight has the utilitarian, no-nonsense look-and-feel of a good piece of army-issue equipment, and it does what it sets out to do. I like it a lot.

The LED Light also, by the way, stock the Sure White PALight, which has a white LED and only the always-on and high-power features, but with a 30 minute auto-power-off feature to stop the battery going flat if the light's turned on by accident. The Sure White is only $US15.50.

Sci-fi lighting

This sleek little item is an Inova X5. It's about 119 by 20mm in size (4.7 by 0.8 inches), so it's pocketable, but you're not going to forget you're carrying it. For its size, though, this is a seriously bright light.

The X5 I got to look at isn't quite the current model - The LED Light stock that, for $US49.95 (on special for $US46.95, as I write this). This previous-model X5 is rather good; the newer version looks to be even better.

The X5's made from aluminium alloy (plain bare-metal anodised finish, or black anodised), and is as solid as a rock. Its lamp has five 5mm LEDs, in your choice of white, red or blue. I got a plain-alloy, blue-LED X5 to play with.

The Inova lamp assembly has a simple spring-loaded peg sticking out of the back of it that stops the batteries rattling, and serves as a switch as well; half-unscrew the lamp end of the light and the X5 turns on. The light runs from a pair of three volt 123-type lithium cells, as used in various compact high-powered "tactical" lights.

If a guy wearing body armour is pointing a gun at you, and if that gun has a flashlight clipped under its barrel, then the light is likely to have 123s in it. More prosaically, 123s are also used by lots of cameras.

123s have the advantage that they're small (34.5 by 17mm) and have impressive capacity - 1.3 to 1.4 amp-hours, into a small load. They've got reasonable tolerance for high loads, too; you can get about a watt out of a 123 without beating it to death. So a light powered by three of them can have a three watt bulb and still manage around three hours of decently bright run time.

Many lights work the 123s rather harder than that, and deliver run times from 90 minutes down to a mere 20 minutes or so. The really low-run-time monster lights aren't normal flashlights; they're meant for intermittent use, for victim-dazzling and target-identification purposes.

The X5 isn't that ferocious. It hauls a couple of fresh 123s down to about 5.8V and draws about 280mA in the process, so you're talking a bit more than 1.6 watts peak draw - eight tenths of a watt per cell. Fortunately, the LEDs aren't eating all of that; if they were, then they'd be driven at something like 325 milliwatts each, which is quite seriously steep. Normal running power for high intensity 5mm LEDs without special cooling is around 100 milliwatts.

This light, like most LED flashlights, is a simple resistor-fed design; the LEDs are in series with a current-limiting resistor. The LEDs in the X5 are all wired in parallel and each have their own little resistor; the thick end of half of the light's power is probably being wasted as heat by those resistors, when the batteries are fresh.

Anyway, the X5's meant to have more than a 20 hour battery life. That's believable. Once again, most of that life will be at reduced brightness, but it won't be as bad as it usually is for LED lights.

The reason for this is that the discharge curve for a 123 cell (see Energizer's PDF-format datasheet for their 123s here, for instance) is pretty flat. When 123s are used in flashlights instead of cameras they don't necessarily get breathing space between discharge pulses, but then again, the X5 doesn't work its 123s as hard as a camera does when it's charging its flash. What all this means is that the X5's batteries, at normal temperatures, should manage better than 2.5 loaded volts per cell (5 volts for the pair) until they're almost 9/10ths discharged. Below that, the X5 should still do OK; in my tests the lamp delivered worthwhile light down to a miserable 3.25 volts, and was still plenty better than nothing at 2.8V.

At or close to its full power, the X5 is bright. This is its output at 1/20th...

...and this is 1/40th, with the blue channel less overexposed.

The quoted 120 foot "effective range" is rather optimistic if you ask me - if your eyes are adjusted to the dark then you'd probably be able to tell a human from a tree by X5-light at 120 feet, but that's about it. At half that range, though, the X5 does very well indeed, and it's a great walking-about light.

This blue one takes some getting used to; single-colour lights make everything look like an alien planet, and they're not much good for reading maps, because anything the same colour as the light will look white.

If that bothers you, of course, you can just get the white-LED version. If you do, though, you'll get a bit less light.

Coloured LEDs are more efficient than white ones, because white LEDs are actually a blue LED with a phosphor coating inside that passes some of the blue, and turns some of the rest of it into red and green to fill out the spectrum. That process eats a fair few photons, and makes white LEDs only about as efficient as a good halogen lamp.

The updated X5, which I haven't seen, has a stainless steel lamp-end (presumably because trauma to the softer end of the original all-aluminium X5 can eventually allow the recessed LEDs to be damaged), a push-button switch (now the tail of the light unscrews for battery replacement, not the nose), and a bigger hole for a lanyard in the tail (the X5 I checked out has a lanyard hole only about 3mm in diameter). And the new model also comes with a nylon holster; the one I got comes with batteries, but that's it.
For more information please visit:
http://www.bossgoo.com/