Generally speaking when shooting portraits, photographers want to isolate the person and nicely blur the background. Unless you are shooting a holiday snapshot, the background is normally unimportant. Therefore that’s what I’ll focus on in this post.
Quick Formula Rules
If I’m photographing one person I use the lowest aperture number my lens will allow, which is normally f/2.8. Note, not all lenses go that low, but good portrait lenses do!
When photographing two or three people, I change my camera’s aperture setting to f/4
Four or more people, I set f/5.6 aperture.
When photographing portraits, it’s important to make sure the people are sharp. Not everyone’s eyes will be nice and sharp if you are setting up a group shot with an aperture of f/2.8. Take this image below for example where I’ve taken a shot of two people on the lowest aperture my lens would go (f/2.8). Notice only one of the models faces are in sharp focus? This is because the blond haired model tilted her head somewhat back further in distance than the other. It wasn’t long before I noticed my error and adjusted my aperture to f/4 using the rules listed above.
Why not simply set a high aperture to start with?
The higher you set your aperture number, the more detail you’ll see in the photo. This isn’t always good for portrait photography. Wrinkles, pimples and other unwanted blemishes will suddenly appear multiplied. The secret to being a great portrait photographer is to hide such imperfections.
Personally I always aim for sharp eyes, but softness in other areas. Take this photo that I shot of a teenage girl below for example.
For this image I set the lowest aperture my lens would allow. Notice her eyes are nice and sharp, yet there is also softness seen in her right shoulder and shoulder blade. Sharp, yet soft at the same time, with no harshness. The lower aperture number also knocked out the background by creating a nice blur, isolating the subject. This particular portrait was taken mid afternoon on a beach. We found a nice dark area with dense tree cover overhead. The background was created from the darkness of shrubs seen further in from where the girl was sitting.
Quick run down on those basic rules again
One person, use the lowest aperture setting your lens will allow.
Two or three people, set an aperture number f/4.
Four or more / group shots, set f/5.6 aperture.
Keep it simple and you’ll never have any problems photographing portraits!