August 18th, 2021
By Daniel Dupont
Regardless of your photography experience, you will eventually be asked to take portraits, whether for friends or family.
Choosing the aperture and depth of field
The key to great photography is to get the right amount of light on the sensor. To achieve this, you have three parameters: the aperture (which is like the lens “door:” it can be wide open or nearly closed, allowing more light or less light depending on the setting), the shutter speed (which controls the duration of the shot) and the ISO sensitivity of the sensor, which allows you to adjust the balance between aperture and shutter speed. The higher the sensitivity, the less light you need to get a correct exposure (not too dark, or too bright), but it may decrease the quality of the photo if you set it too high.
The aperture, represented by the f/ value, allows more or less light to reach the sensor through the lens.
Understanding the aperture is essential to take beautiful portrait photos, as it controls the depth of field – which gives the blurry background effect. The more your lens is open (f/2.8, large aperture, low value), the more light will reach the sensor and the shallower the depth of field will be - so for a very blurry background, choose a lower f/ value.
Conversely, the more your lens will be closed (f/22, small aperture, high value), the less light will pass through the lens to the sensor and the more depth of field you will get. But it is actually pretty rare to make portraits at such an aperture.
What is depth of field?
The depth of field is the area of sharpness of the image and it varies depending on the aperture, how far the subject you’re focusing on is from you and the focal length of the lens, e.g. 18mm, 50mm, 100mm etc. At the same aperture (or f/value), the closer the subject is to you, the shallower the depth of field will be. Conversely, the farther away the subject is from you, the greater the depth of field will be.
More powerful lenses can create a shallower depth of field, which can be interesting for portraits. Your subject stands out against a more discreet background.
However, you must pay close attention to the accuracy of the focus if you are working at shallow depth of field, especially if you are close to your subject. It's important to remember that depth of field is distributed in space very precisely, 1/3 in front and 2/3 behind the point where the focus is set.
PRO TIP : If you are new to photography, I strongly recommend that you memorize the maximum apertures of your lenses and understand the results when using them.
Choosing which camera lens to use:
The use of zoom lenses is interesting in portrait photography, given its versatility. You don't have to move around to get the desired composition, as you can vary the framing by adjusting the zoom.
Choosing the right aperture:
It is one thing to know the effects of the aperture, but making the right choice still requires some thought. This choice is based on a good understanding and careful consideration of certain factors, such as the intensity of the light source and whether you should use a tripod or not.
If I am photographing a person indoors, there is not much light, and I am using a bright lens (capable of a large aperture), then I choose an aperture between f/1.8 and f/4.
In bright light, you have more flexibility in the choice of aperture and you can set it to a value that offers more depth of field without having to increase the ISO sensitivity
Tip: Be sure to choose a shutter speed that is fast enough to avoid blurriness caused by your subject moving. Even if you have camera or lens stabilization turned on, make sure to really freeze the motion.
For the majority of the portrait photos I take, I select an aperture value between f/5.6 and f/9. This way, I can get enough depth of field to focus properly on the person without the background becoming too visible.
When I shoot a portrait while traveling and I want the background to be more present, I prefer an aperture between f/8 and f/11.
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