I've posted this before :
The Better Beamer is a couple of plastic 'arms' with velcro (the photos make it look like it's a solid unit but it's empty space both above and below - just clever product photography) and a small plastic 'Fresnel lens' that you stick on front, again with velcro. It probably costs less than $5 to produce and enterprising young (and old) men could probably make a very decent attempt at building their own.
However I am not one of them. Had I been in the USA I could have just paid my $40 and walked away .. in China however it cost me $75 as the blighter's haven't copied the damn thing yet
Anyway. What you get for your money is ...... brilliant for birding ! There is a rather large increase in the amount of light directed in the direction of your subject as the Fresnel magnifier goes to work and of course the snoot targets that light. I'd say it's possibly a 30-40% increase over flash alone.
The (poor) test shot below was (if I remember correctly) 1/32 power (Metz 50-AF1) @ 15M. I have another I took last night of a pigeon on a neighbour's rooftop at 40m @1/1 power, that was too much I fear as the flash reflection is strong in the bird's eyes and I think 1/2 power would have sufficed. 50M at full power should be doable .. and this could well transform my birding as the little #$%$#$ almost always see me, even when doing my best SAS impression, when I get within 20m !
So is this piece of plastic worth $40 ... absolutely not. Is it worth $75
to me ... that would be a definite Yes !
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What I'll add to that Dave is that I almost always switch to manual metering and manual flash. A few tests shots on a tree branch and you're good to go. Usually 1/16 or 1/8 power is enough for <10m, 1/8 or 1/4 for <15m and < 1/4 or 1/2 for 20m (all with the birds in dark bushes or canopy) and this helps keep your ISO down, just adjust to taste. This also helps the recycle times on the flash.