The Better Beamer
The Better Beamer is a flash extender. It's a very simple and remarkably cheap device: two stiff but springy plastic arms about 15cm long, a rectangular plastic fresnel lens a bit bigger than a postcard, and a velcro strap.
At the rear end of the plastic arms they become curved to be the same shape as your flash head; at the front they have some velcro: the fresnel lens has matching velcro strips that mate to the flash arms.
To use it, you simply attach the arms to the fresnel lens, then slip the other end of the arms over the sides of your flash. It is very light and will sit there quite happily while you fish around in your pockets trying to remember where you put the velcro mounting strap. Then you wrap the strap around the arms, binding them firmly to the flash head.
The Better Beamer lens focuses the output of your flash, making it possible to use a long telephoto lens for flash photography where, with just the flash head alone, you couldn't throw nearly enough light on a subject.
Why do you need a Better Beamer?
Most modern flashes have the ability to zoom. My Canon 580EX-II, for example, covers the range from 24mm to 105mm. (Or, using a 1.6 crop camera like a 40D, it can illuminate the range between 15mm and 66mm.) It's smart enough to auto-detect the focal length I'm shooting at and auto-match so that it always illuminates all of the scene I'm taking, and doesn't waste any precious flash power lighting up things outside my field of view. It's also smart enough to work out if I'm using a full frame, APS-H (1.3 crop) or APS-C (1.6 crop) camera and adjust itself to suit.
But what if I'm shooting at 210mm? It can only zoom in to 105mm equivalent, so doesn't that mean half my flash power is being wasted on things outside my camera's field of virw? Nope: it's worse than that. I'm wasting three quarters of the flash power. With a 210mm lens on a full frame camera (or a 130mm lens on a 40D), only one quarter of the light put out by the 580EX-II (or pretty much any other flash) is illuminating the subject. Go to a typical bird photography focal length - leyt's say 400mm on a 40D or 500mm on a 1D II, both of which work out to 640mm full-frame equivalent, and you are getting 2.7% flash effectiveness.
As you can see fom the figures above, using a 40D with a 400mm lens and a 580EX-II, 97% of the flash power is wasted on illuminating areas of the scene which the camera will never see.
Flash zoom 35mm FL APS-C FL Flash effect
105mm 105mm 66mm 100%
105mm 150mm 130mm 50%
105mm 300mm 188mm 12.5%
105mm 640mm 400mm 2.7%
The purpose of the Better Beamer is obvious: by refocusing the light from your flash into a narrower beam, you waste less power, and can take flash pictures from further away. Or use higher shutter speeds. Or just work the flash a bit less hard, keeping it cooler longer and getting better battery life.
Better Beamer in practice
In practice, the Better Beamer still wastes a lot of light, but ultimate efficiency isn't necessary. Even a tiny improvement on the woeful <3% efficiency of a standard flash gun at 400mm makes a massive difference, and while I haven't tried to calculate the Better Beamer's efficiency, it's certainly way, way better than the 2.7% you get without it. 20% maybe? Just a wild guess. Whatever the amount, it's enough to do the job with power to spare, certainly on the big 580EX-II, and probably with any flash you are likely to try with it.
The down side is its fiddly, cumbersome nature. It wobbles around a bit on your flash head (which doesn't seem to matter much), and, worse, you soon discover that the flash head you thought so stable and solid is actually itself quite a wobbly thing. There is only a tiny bit of play in the 580EX-II tilt/swivel head design, maybe a half a degree or so, but it's enough to make life awkward. Worse, the 580EX-II (and no doubt any other flash you are likely to own) doesn't sit parallel to the lens: it's designed to angle very slightly down to compensate for the off-centre, slightly elevated position it sits in mounted on your hot shoe.
At, say, 85mm focal length, this works perfectly to give you full illumination of your scene with very little light wasted, but as you go to longer focal lengths, getting the narrow beam of the Better Beamer lined up with your narrow field of view is a tedious matter of trial and error.
In my case, I'm using a stand-off extension bracket to lift the flash (and Better Beamer) up 40-odd centimetres above the camera. This is pretty much an essential if you want to avoid red eye and other ugly flash effects. And, of course, it makes lining the damn thing up trickier still.
In the end, I have decided that the only practical way to do it is to take a series of test shots of some static object at the same distance from you as the bird is going to be, tweak it until you get a good allignment, then hope like hell that the whole rickety contraption doesn't shift when you least expect it to. The Better Beamer, in other words, is not something you can hope to use successfully for quick, fleeting opportunities. It's got to be planned and methodical all the way. "Tedious" is a good word for it, and "frustrating" another.
By far my best successes with the Better Beamer have actually been at very close range - so close that you could manage perfectly well without the flash extender, but [b]not[bi] at the sort of shutter speeds you need for birds. With the Better Beamer, I can take frame-filling pictures of tiny birds like pardalotes and thornbills with a 500mm lens and close-up rings, in hopeless light, and still be working in the 1/800th to 1/2000th shutter speed range, at ISO 400 or 500, and anywhere between f/4 and f/11.
Obviously, this is well past flash synch speed for any camera: it's all done with high-speed flash, which is very hard on the flash gun and simply wouldn't be possible without the Better Beamer.
You will find a zillion examples in my Scrubwrens always make me laugh thread.