Credit: Jeffrey Ufberg/

Powder (on) your nose!

Outside of The Late Show with David Letterman in NYC Wednesday, a chipper Ellie Kemper was unknowingly committing a major makeup fax pas -- sporting white HD makeup face powder before she hit the TV set.

Face powders like the one sitting atop the Bridesmaids actress' nose are formulated to be translucent and flatter all skin tones. Its purpose is to keep shine at bay and deliver a flawless airbrushed skin effect for the HD cameras.

The problem is, not only does the microfine makeup show up in non-HD light (like the one of a camera flash) but it also pays homage to another white (illegal) substance that's quite scandalous.

But Kemper, 31, isn't the only star who has been spotted in the white stuff  -- Nicole Kidman was photographed in 2009 with a mess of white under her eyes and on the tip of her nose while Eva Longoria was snapped with the same look in January 2011.