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Every starting photographer knows that the aperture of the lens controls the amount of light that enters the camera. The bigger the aperture, the more light reaches the camera sensor.
However, the aperture has a second function of equal or even higher importance. The choice of aperture will determine what our image will look like in terms of sharpness.
The goal of this article is to help you figure out when to use big or when to use small apertures, regardless of the light conditions.
Aperture and depth of field
As I said, the size of the aperture determines the amount of light that enters the camera. But, besides the light, aperture directly affects the depth of field in your images.
By Depth of Field (often abbreviated DOF) we mean the area of acceptable sharpness in a photograph. When DOF is shallow, just a small part of our image appears sharp. When it’s large, our photo might look sharp from foreground to background.
Important: The more you open your aperture, the shallower the depth of field and vice versa: the more you close it, the larger it gets.
Shallow or large depth of field – which one do I need?
The choice of depth of field depends on the type of photography you want to do.
If you want to take photos of landscapes, you would want images that are sharp all over. Hence, you need to create a large depth of field, using small apertures starting from f/8.
If, however, you want to shoot portraits with a blurred background, you need to open your aperture wide (preferably choosing f/2.8 or above), in order to have a shallow depth of field.
Creating large or shallow depth of field with aperture
Since we understand now how aperture selection affects depth of field, let’s see how this works in landscape and portrait photography.
When shooting portraits, you need to visually separate your subject from its surroundings. Ideally, you should have a sharp subject that stands out against a blurred background.
Here’s how to achieve that:
a) Use aperture priority mode
This mode allows you to select apertures without having to think about shutter speeds. To me, that’s the most convenient way to photograph, especially when you’re most concerned with your depth of field.
b) Choose the widest possible aperture
Select the widest possible aperture your lens supports. A good fast lens allows you to open the aperture up to f/1.4 but f/2.8 works great too.
c) Use a longer focal length
If you can, use a lens with a focal length bigger than 50mm. An 85mm lens is ideal for portraits. If you have a zoom lens, make sure you’re shooting with the longest focal length it supports.
d) Get closer to your subject
The closer you are to your subject, the shallower the depth of field will be.
With landscapes, you want a very large depth of field. Your goal is a photograph where everything (or almost everything) appears sharp – from the flowers in the foreground of your photo to the mountains seen behind.
Here’s how to do that:
a) Use aperture priority mode
Again, you’re going to be mainly working with aperture here, so choose this mode and don’t bother about shutter speed. You’re most likely shooting with a tripod anyway.
b) Choose an aperture between f/8 – f/11
An aperture in the range of f/8 – f/11 can yield an image that is sharp all over.
You may use even smaller aperture, but generally, the optical quality of your lens is best at the middle of the aperture range it supports.
c) Use a small focal length
The smaller the focal length of your lens, the larger the depth of field you can achieve. You are not likely to make a mistake here since small focal length lenses are also wide-angle ones. And if you shoot landscapes, you certainly have one of these.
d) Focus one third into the frame
If you focus at one third into the frame, you may get a photograph that is maximum sharp from foreground to background. This one-third focus point is known as “hyperfocal distance” and you can find the exact one for your lens using online calculators.
If you want to know more about hyperfocal distance, check this article.
Is the topic less confusing now?
Did the article help you understand how you choose right aperture? Or do you still have any questions? Let me know in the comments below.