A human face is three-dimensional. When shooting a human face at close range, if the aperture used is too large, other parts of the face that are not focused may become too blurred. Let’s learn about an f-number that is convenient for taking close-up shots in portrait photography. (Reported by: Teppei Kohno)
f/2.8 is the optimal f-number for capturing facial expressions
When shooting a human subject up close with a lens that has a small maximum aperture, care is required to not open the aperture too much. This is especially so when shooting from an oblique angle, where the three-dimensionality of the face will be emphasised and the bokeh effect, magnified. If a large aperture such as f/1.4 is used, only a specific portion of the face is in focus, which can obscure the facial expression and make it look ambiguous or indistinct. To fully capture the facial expression while reproducing a background bokeh effect, f/2.8 is a good f-number to work with. The focusing range extends all the way to the rear of the eyes, nose and mouth, allowing the facial expression of the human subject to be fully captured since the sharpness of the depiction is higher compared to that of the maximum aperture.
FL: 85mm/ f/2.8/ 1/25sec/ ISO 400
Shot at f/2.8: The eyes, nose and mouth are all in proper focus. As the entire face is rendered with clarity, the facial expression is unambiguous.
FL: 85mm/ f/1.2/ 1/125sec/ ISO 400
Shot at f/1.2: The bokeh effect is too large with only the nose in focus and the eyes in front blurred, which makes it hard to be sure of the facial expression.
Tips for even more effective use of f/2.8 in portrait photography
Scene 1: If your photo turns out awash in white…
In well-lit scenes such as outdoors in broad daylight, an f-number of f/2.8 could allow too much light to enter the lens, resulting in overexposure. Try shooting somewhere with more shade, or increasing your f-number. You could also use an ND filter, which is attached to your lens to restrict the amount of light entering it.
To learn more about ND filters, check out this article: Lens FAQ #5: What are the Pros and Cons of an ND Filter?
Scene 2: If you want to get a slightly bigger bokeh…
After reviewing your shots, if you decide you need a bigger bokeh, try shooting with a smaller f-number such as f/2.5 or even f/2. This decreases the in-focus area of the image (i.e. gives a shallower depth-of-field). However, with this comes the risk where being even the slightest bit off-focus results in a shot that is completely out-of-focus. Make sure that your camera is held stable and secure, and increase your shutter speed. To balance that out, increase the ISO speed too.
Focus on the eye in front for the portrait
When shooting a human subject up close from an oblique angle, remember to focus on the eye in front. If the focus is on the front eye, the facial expression looks good in the finished photo even though the eye at the back is a little blurry.
FL: 50mm/ f/1.8/ 1/125sec/ ISO 250
Shot taken with the focus on the front eye. The image looks lively even if the background is a little blurry.
FL: 50mm/ f/1.8/ 1/125sec/ ISO 250
Shot taken with the focus on the eye at the back. The blur in the front area is evident, and causes the overall image to appear indistinct.
Setting to f/2.8 in the Aperture-priority Mode For EOS 700D
1. Set the camera to the [Av] mode
Turn [ON] the power supply and adjust the Mode Dial to the [Av] mode.
2. Turn the Main Dial
Turn the Main Dial to change the f-number.
3. Check that the f-number can be set to f/2.8
Check that “F2.8” appears on the rear LCD screen in the area circled out on the image. Take the picture after confirming.
Born in Tokyo in 1976, Kohno graduated with a Social Work degree from the Department of Sociology of Meiji Gakuin University, and apprenticed with photographer Masato Terauchi. He contributed to the first issue of photography magazine PHaT PHOTO and became an independent photographer after that, in 2003. The author of many books, Kohno not only shoots all sorts of commercial photographs, but also writes prolifically for camera and other magazines.