Taking photographs is great. It’s even better when you can get “that cool effect where the background is all blurry.” This can really make the subject pop and stand out from an otherwise busy background. It can also give your photos a sentimental quality.
Your camera lens can actually only focus on a very tiny point in space, but there is an area around that point that will appear in focus in your photo. The space before and after your focal point that is in focus is referred to as the depth of field. A large depth of field describes an area where a large amount of the image is in focus; in other words the whole picture is clear. A shallow depth of field occurs when a small amount of the picture is in focus; the subject is clear and you have the “cool blurry background.”
To achieve a shallow depth of field, there are a few factors you have to keep in mind when shooting the subject. Three of the main factors are aperture/f-stop, lens size, and distance to the subject.
Example of shallow depth of field
Aperture or f-stop refers to the opening of the lens. If you look into your lens and adjust the focus, you can see the opening size change. Aperture determines the amount of light that is let into the lens to create the image. The numbers that refer to aperture range from 1.0 to 64 but are usually around 2.8 to 22. The smaller the number, the larger the opening, and the more light that is let in through the lens. This is probably the most important part of creating a shallow depth of field. The larger the opening, the blurrier the background will be. A small aperture makes the background sharper. This can be confusing, especially since knowing the aperture scale can be tough to remember to begin with.
The next factor in creating a shallow depth of field is the lens length. A longer lens creates a more shallow depth of field. This is because the light has to travel a further distance through the lens to create the image. Photographers who do macro shots of insects or other animals often achieve this effect easily since their lenses are much longer than normal. If you are using a shorter lens, such as a wide-angle lens, the depth of field will be much larger, and more of the image will be in focus.
Example of large depth of field
Distance to the subject is one more thing to keep in mind when determining your depth of field. The closer the subject is to the camera lens, the less depth of field there is. This is why landscapes are so crisp and in focus, because rolling landscapes are far away, resulting in a larger depth of field. Taking a photograph of something that is very close to the lens, like a flower, results in a blurrier background or a shorter depth of field.
All of these factors for creating the proper depth of field can seem like a lot of information to remember, but an easy way to think about it is to think of how your eyes work. Camera lenses try to mimic the eye, so it would be obvious that they would work in similar ways. If something is out of focus, we automatically squint our eyes. This gives our eyes and pupils smaller openings, much in the same way that a lens uses a smaller opening to create a less blurry background. When an object gets closer to our face, we focus more on that object and on less of the background. Try it with your hand by holding your hand (or an object) at arm’s length. Now move it closer, and the items around your hand become less in focus. The same principle applies. The only rule that doesn’t exactly apply to our eyes is the lens length. The easiest way to remember this is to think of a long lens taking a picture of a tiny bug.
Depth of field, when used properly, can really make or break your images. Overusing a shallow depth of field can lead to an amateur feel for your photos, or even look like a mistake. Make sure that the subject you are shooting is something that does not rely on the background and will still make an impact even if it is shot by itself. Examples of this are flowers, pictures of a person’s face, or even something that is repeated, like a row of chairs; more often a subject that is closer to you. A long depth of field is more useful for something like landscapes or a crowd, usually something further away. Utilizing depth of field properly can really help to add a little something extra to your photos, and can give them a polished, professional touch.