In ten years of running a photography rental studio, I've learned to pick out the inexperienced shooters immediately. Here's a dead giveaway: They tell you that they want to start off with the Super White backdrop, then change to Fashion (light) Grey, then change to a Thunder (dark) Grey, even though each change costs $20. The pro simply sticks with the Super White, then stops their camera up or down along with the lights to turn the white background into whatever shade of grey they want.
To do the latter requires an understanding of aperture/shutter/studio lighting. For those of you bred on smartphone photography whom are looking to switch to single-lens reflex, and don't know your f-stop from your L-train, here's a handy reference guide that will at least get you started:
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That was thoughtfully put together by Daniel Peters of the Fotoblog Hamburg.
By the bye, aspiring SLR photographers among you: If you require more explanation of how you can change a white backdrop to grey just by monkeying with your set-up, you can watch photographer Robby Ticknor figuring it out and explaining it below. (While he doesn't go as dark as Thunder, he gets it past Fashion Grey for sure.)