This is something I was experimenting with for the recent contre-jour challenge but didn't use (the sun-rise was much prettier).
It's a short length of flexible aluminium tube with a plastic cover from a reel of sticking plaster inside sitting on a red filter which has a microphone grill on top. This stack is on top of a piece of black plastic with a hole in, on top of a flash-gun. I'll put a link in to some photos when the challenge is over.
Processed using Gimp 2.6.7
curves
re-size
sharpen
The parts:
and the set-up:
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