For much of the film era, 35mm protraitists opted for focal lengths between 70mm and 135mm. Why? Because they flatter the human face – they’re neither long enough to compress space, which flattens contours, nor wide enough to expand a large nose. This pushed the 50mm lens out of the portrait business.
But then came digital. Because of the lens-conversion factor associated with most DSLR cameras, the too-wide-for-faces 50mm converts up to 75-80mm – perfect for half-length or even head and shoulder portraits. (Don’t get any closer, though.)
The 50mm f/1.4 also beats “portrait” (105mm f/2.8 or 135mm f/2.8) lenses, allowing convenient working distances and beautifully out-of-focus backgrounds. For a half-length portrait made with a 135mm, for instance, you typically must put 12 feet or more between camera and subject. That kind of space can be hard to come by or work with – you may have to shout to be heard. With a 50mm, though, you can step forward to fix Junior’s tie, then take a few steps back to click the shutter.
And if you want the kind of dreamy background, nothing’s better than the f/1.4’s extremely shallow depth-of-field.