Choosing a lens for portraits

Most portraits that feel “right” have one thing in common: the background has dissolved and the person stands clear of it. That comes from combining a short telephoto focal length with a wide maximum aperture.

Why 75–135mm equivalent

Get close to someone with a wide lens and perspective exaggerates whatever is nearest the camera — usually the nose. By around 85mm equivalent that distortion has essentially gone. Longer still, and the background compresses, which separates the subject further.

Past 135mm you have to stand a long way back, which is awkward indoors. 85–135mm sits in the usable middle.

The lower bound here is 75mm rather than 85mm so that lenses like a 56mm on APS-C (84mm equivalent) and full-frame 75mm primes are included. They fall short on paper but are used for portraits constantly — and in a small room, the extra bit of working distance is welcome.

Aperture trades blur against keeper rate

An f/1.4 lens does blur beautifully, but the plane of focus is a few centimetres deep. You aim for the eye and land on the eyelashes. Something in the f/1.8 to f/2.8 range blurs plenty while leaving margin for error.

How much a lens actually blurs is hard to judge from a number, so use the sample photo link on each lens page and look at real images.

Prime or zoom

Primes are brighter, lighter and cheaper. A 70-200mm f/2.8 is heavy and expensive but lets you recompose without moving your feet, which matters when the subject is moving or you cannot choose where to stand. The usual advice holds: a prime for your first portrait lens, a zoom if you are shooting weddings or events.