Creating the perfect image with your camera can be a very complicated process. There are a lot of different factors that come into play when setting up your shot. Your camera has several different controls, and all of these need to be manipulated in such a way that they create the right balance of light in your image.
It might be helpful to think of this process like a mathematical equation. Do you remember those complicated equations in high school algebra class? You had a bunch of numbers and letters — or variables — on one side of the equation, and then on the other side of the equation, you had another set of variables. If you changed something on one side of the equation, then you had to adjust something on the other side of the equation to make it balance out.
Capturing light and images through your camera is a very similar idea. Just as you have different variables in a mathematical equation, you have different variables that go into each photo. You have to balance out your shutter speed, aperture, ISO and exposure balance. If you adjust one of these controls, that will throw off the exposure. So you then need to adjust a different control to bring your exposure back into balance.
So let’s talk specifically about aperture and how manipulating this variable will affect the images that you create with your camera.
High Aperture vs Low Aperture
The term aperture technically refers to how wide your shutter opens when you take a picture. Aperture is measured in f-stops, which are notated on your lens by the letter “f” followed by a slash and a number. A small aperture has a high number, while a large aperture has a small number. I know it sounds a little bit backward, but that’s the way the photography gods decided to do it.
A large aperture would be something like f/2.8 or lower, while a small aperture would be in the double digits. So how do you know when to use a large aperture or a small aperture? Below are four ways that manipulating your aperture selection affects your final image.
How Does Aperture Affect Exposure?
The first thing to consider is that using a large aperture allows a large amount of light to come through the lens onto your image. So when you use a large aperture and have that lens wide open, this will often result in a brighter image, unless you adjust other camera settings to darken the image.
In a similar way when you go with a smaller aperture, less light will be allowed to come into the image and that will result in a darker exposure. So when you adjust your aperture in one direction then you’ll need to compensate for that by adjusting your shutter speed or ISO to balance out the amount of light in your image.
So if you are working in an area where there is not much light such as a live concert hall, you might want to use a lens that allows for a large aperture, such as a f/2.8 or f/1.4. These larger apertures will bring in a lot of light and allow you to use a faster shutter speed.
How Does Aperture Affect Depth of Field?
The depth of field refers to the area within the image that is in sharp focus. A very large aperture such as f/2.8 or lower will result in a very narrow depth of field. This means that a narrow slice of your subject will be in focus and everything closer to the camera and further from the camera will be blurred out.
In some cases, an aperture of f/5.6 or even f/8 can still result in a blurred background if the subject is much closer to your camera then the background. Blurring out the background like this really makes your subject pop out from the rest of your image. This is known as the bokeh effect, and it is a favorite technique among sports photographers and portrait photographers.
Landscape and real estate photographers, on the other hand, will want to use a smaller aperture to allow for greater depth of field. By using a f/22 aperture setting, for instance, everything in the image from front to back will be in much sharper focus.
How Does Aperture Affect Focus?
When you use a large or wide open aperture setting, the very narrow depth of field makes focusing more of a challenge. If you are shooting a pet or human subject, you should focus on the eye to keep the eye as sharp as possible. If you’re subject is moving, then this can be pretty tricky. It’ll take a lot of practice, but it will also result in a pretty amazing portrait.
If you are finding that the images are still a little bit blurry due to your subject moving in and out of focus, then try closing down your aperture to f/8 or so to allow for a little bit more depth of field.
How Does Aperture Affect Video?
When it comes to shooting video, the same principles will apply. The larger aperture will result in a brighter image and allow you to use faster shutter speeds and a smaller ISO. These can give you better color saturation, finer grain, less digital noise and less motion blur.
The trade-off is that your depth of field will be narrower, so a moving subject might be more difficult to keep in sharp focus. A smaller aperture will give you better depth of field and sharper focus on your primary focal point, but the other camera controls will need to be adjusted to balance out the exposure.
So in the end aperture is just one of the many factors that you control with your camera and lens. A large aperture can result in a brighter image, less motion blur and blurred out backgrounds, while a small aperture can darken the image, increase the depth of field and produce sharper focus from foreground to background.
There is no single best setting when choosing your aperture. It all depends on the effect that you are trying to create in your image. The more you practice, the better you’ll understand how to manipulate aperture to create the kind of image you want.