Sunglasses hide a myriad of sins. Bad hangovers, tears, last night's smudged mascara and the evidence of years of fun living.
They are also a great equaliser. Celebrities wear them to blend in. Us mere mortals don them to feel glamorous, to stand out.
Famous faces from Andy Warhol to Elvis Presley, Clint Eastwood and Catherine Deneuve have been photographed with their eyes shrouded by the coolest tinted frames.
A book by Lauren Goldstein Crowe, 50 Shades, a shameless play on the success of EL James' "mummy porn" trilogy, hits coffee tables this month.
Here are a few choice examples from a collection of 50 iconic images from 50 years of popular culture.
50 Shades (RRP £19.95) is published by Reel Art Press, www.reelartpress.com
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