Depth of field is a essential part of photography and being able to master it can take your shots to the next the level. Because of it's usefulness, any photographer should make the effort to understand how to control the depth of field in their images. This task, however, is more easily said than done for many. There is a whole lot of science and math that can explain depth of field quite precisely and you should, at some point, take the initiative to study it. . But, as a primer and to quickly get you on your way to mastering depth of field, here a few quick tips you can use.
What is Depth of Field?
To explain it layman's terms, depth of field, or DoF, is the amount of image that is in focus. A shallow depth of field will be mostly out of focus, with only a small portion of the image appearing sharp and crisp. Whereas, a large depth of field will have a deeper look since most of the image from the foreground to the background will appear sharp.
Here are a couple of examples:
Shallow Depth of Field – A shallow depth of field is useful for when you want to draw the viewers eye to certain aspect of the scene, such as in macro photography. Another good application of a shallow depth of field is when you want to blur out a distracting background, like I've done in the following portrait.
Large Depth of Field – In the photo below, we can see that a large depth of field really comes in handy when you want to show off a wide portion of the scene such as in landscape photography.
Now that you have an idea of what depth of field is, and how you can use it create more compelling photographs, there a few ways you can learn to control it. We'll start with the most obvious and widely known one first:
- Aperture – One of the first things we learn in our studies as photographers is about aperture. Not only does it control the amount light that passes through the lens, but it also affects depth of field. The wider, or larger, your aperture is the less depth of field you will have. Shooting wide open, say at f/1.8, will create an image in which there is a small section of in focus subject matter. Conversely, an aperture of f/22 will produce an image that is entirely in focus. What this means is you can adjust your aperture to control the amount of depth of field you'll have in your image.
In this photo, which was shot at f/2.5, the depth of field starts just past the cats nose and begins to fall off around her ears. This shallow depth of field draws the viewers eye to the subject, which is the cat's eyes.
Tip: If you want a shallow depth of field, but a wide aperture lets in too much light, try using a neutral density filter which will allow you stop down the light without having to sacrifice shutter speed.
- Distance To Subject – By moving closer or farther from your subject, you can change your depth of field greatly without having to adjust your camera settings. An easy exercise you can do to practice this concept is to grab an assistant and your tripod and take a photo of your assistant at varying distances. Setup your tripod in an open area with your camera set to a middle of the road aperture such as f/8. Try to use a typical portrait lens at 70mm. Without changing the camera settings or location of your tripod, take a few pictures of your assistant having him move 15-20 feet backwards for each shot. You will notice that the images in which the assistant is closer to your camera, you will have a more shallow depth of field. The shots where your subject is farther away will have more area in focus.
- Consider Your Lens – One last consideration is your lens choice. Not only will some lenses be faster (i.e have wider apertures) which will affect depth of field, but the length of the lens will also play a part in it. As a rule of thumb, remember that the wider the lense, or shorter the focal length, the deeper your depth of field will be. For this rule to be most useful, you must really keep in mind your aperture settings. To practice this, have your assistant stand about 25 feet away from you. Outfit your camera with zoom lens that allows you to shoot relatively wide and relatively long, like a 28mm-200mm. Set your aperture once again to a middle of the road f/8. This time without moving your camera or your assistant, take three more images of him: one with your lens at 28mm, a second with your lens at 70mm, and a third with your lens fully extended to 200mm.
Look at the difference in depth of field between the two focal lengths in the following photos.
From this exercise you'll learn that the telephoto effect you get when you are closely zoomed in on your subject at 200mm creates a very shallow depth of field in comparison to the image at 28mm, which has more of the surrounding area in focus.
To get a better idea of depth of field and its relation to aperture, take a look through Flickr user, davidd's album, Canon Lens Comparison, by clicking on one of the two images found in the last exercise. Browse through his images and pay close attention to the focal length and aperture settings so you can compare them and use that information to your advantage next time your out shooting!