Many amateur photographers don't know what aperture to shoot headshots at. Most of the really new headshot photographers who have not yet invested in lenses dedicated to shooting them will wind up using a kit lens with a very small aperture. I highly advise against this because kit lenses don't work for headshots unless you are extremely experienced and use at least a 200 mm focal length.
Instead, buy one of the lenses I recommended in the last chapter and take some test shots at different apertures to learn what the effects are. Make sure that you use a human subject. If you shoot a random object, you won't learn how the different apertures effect what the face looks like compared to the background.
Shoot telephoto lenses with a slightly closed aperture and shoot wider-angle lenses with a slightly wider aperture. You'll notice that as you open the aperture wider and wider, the depth of field decreases and the subject’s ears begin to blur when you focus on their eyes. This is something that you don’t want if you can help it.
Most beginning headshot photographers think blurring the subject’s ears is good because having such a shallow depth of field looks professional. In all honesty it's not that nice to look at, especially if it’s overdone. It winds up looking as though the subject is swimming in a pool of blur, and the only things not under the blurring pool are their eyes and the front of their face. It's actually a bit weird. This effect is more noticeable when shooting at a faster aperture than f/2.
The best look is a subject whose head is mostly in focus where the only thing noticeably blurry is the background. This way, there is no strange blurring to distract the person looking at the photo, and the viewer can focus totally on the subject’s face.
The following are some good numbers you may want to write down. I use this simple formula to determine what aperture to shoot with and at what focal length:
For every doubling of focal length, aperture must close by one stop.
Begin at 100 mm = f/2.8
You should start the formula with 100 mm and f/2.8. Using this formula, it's easy to see that if you plan to shoot at 200 mm, you will need to close the aperture down by one stop to an f/4. If you decide to shoot at 50 mm, you should open the aperture one stop from an f/4 to an f/2.
By following this formula, you will know what aperture to use at different focal lengths to avoid blurring of the ears too much. Of course you can just experiment, but it's a good thing to know in your head so you’ll appear more professional to your clients. It’s better to know the exact camera settings instead of telling the subject you are going to take a few test shots to see what camera settings look good.
Remember: try to avoid shooting headshots at the widest possible aperture. Lens optics won't be as sharp and you may wind up dealing with purple fringing and lens flare, things you definitely don't want in your headshots. They will definitely be distractions and you'll have to somehow remove them later in Photoshop. Therefore, always close down the aperture by at least half a stop from the maximum of the lens. This is why it's good to buy lenses that can open very wide, even if you don't plan to shoot that wide. It results in much sharper glass.
But remember that lighting definitely has to do with what aperture you'll use. If you are shooting outdoors as the sun is setting and you're running out of light, then it's okay to use the maximum aperture, even if the subject's ears look a bit blurry. It's better than having distorted colors and horrible amounts of grain in the shot.
NY: 2 West 46 Street, Suite 1500
NJ: 611 N Maple Ave., Suite 9 – Ho Ho Kus
CO: 2640 South Garland Street