I have them, and they're fun to play with
I can get you some shots that show the difference between with/without them tomorrow.
Here's a few i took for the IC photo thing:
All 3 tubes, a relatively narrow aperture:
All 3 tubes, at f/2.2 aperture:
Some salt. All 3 tubes, f/4.0, external flash off to the right.
Cog on my bike: