Before Photoshop, artist Gil Elvgren (wiki) relied on the technique of painting from a photograph of a model instead of from the live model. His classic pin-up pictures of curvy-girl-next-door types with their skirts billowing adorned the noses of bombers and the walls of soldiers barracks in the 1940s and '50s. In addition to dozens of calendars, he illustrated stories for a host of magazines (such as The Saturday Evening Post and Good Housekeeping) and also provided advertising images for Coca-Cola, General Electric and Sealy Mattress Company, among others.
As the '70s approached and the pin-up girl craze started to die, Elvgren was down to one business account. When he died in 1980 he was broke, and his last work was published posthumously. In the last few years there has been a resurgence of interest in the pin-up girls, and Elvgren's work in both advertising and calendars has become highly collectible - in 2012 one of his classic pin-ups sold for $176K. In 1998 Elvgren's youngest son Drake produced a 200-page coffee table book includes hundreds of photos of Elvgren's work entitled Elvgren: His Life & Art.
Even if you're too young to remember any of these specifically, they're so ubiquitous that they probably look familiar. Below are some of his paintings, alongside the photos on which each was based.