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Why Use Depth of Field?
Controlling the amount of the photo that is in focus is one of the photographer’s best tools to help draw the viewer’s eye where you want it. For example, landscapes are typically shot so that everything is in focus, so photographers will shoot at small lens apertures (e.g. f11 or f16).
But you can create layering in your image by having only part of the photo in focus. If you have some foreground objects out of focus (for example, some leaves), they will give your image depth; the viewer will really feel like they’re looking through those leaves at your main subject. To achieve this effect, shoot at a wider lens aperture (e.g. f/2.8 or f1.4).
What Factors Affect Depth of Field?
A few different factors affect depth of field.
Learn more about the factors that do affect depth of field below.
Being able to understand how aperture affects the relationship of a subject to its background is one of the first steps to becoming a better photographer. Aperture is how big the opening is that lets light in, expressed in F-stops. F-stops are counterintuitive, because the larger the number, the smaller the opening. So a small f equals a large aperture.
For example, f2.8 allows twice as much light into the camera as f4, and 16 times as much light as f11. Aperture affects the depth of field: larger openings create a shallower depth of field, while smaller openings make more of the image in focus.
2) Camera-Subject Distance
Camera-subject distance is the distance between your camera and your subject. The shorter the camera-subject distance—or, in other words, the closer you are to your subject—the shorter the depth of field.
Envision you have eight feet of space in front of you, before you hit a wall. If your subject is flush against the wall and your camera is eight feet away, the depth of field is zero (and the desired effect won’t show in your image). Now imagine your subject moves to within a foot of the camera. Suddenly, the depth of field has grown, and the effect will render in your image.
3) Focal Length
The focal length of the lens contributes to depth of field: a longer focal length corresponds to a shallower depth of field and a shorter focal length corresponding to a longer depth of field. Generally, wide angle lens have a deeper depth of field than telephoto lenses (aka zoom lenses).
4) Sensor Size
Sensor size is the final important factor in depth of field. If the other factors are the same—aperture, focal length, camera-subject distance—a larger sensor will have a shallower depth of field. In general, cameras with smaller sensors have larger depths of field.
Sensor sizes vary between models of cameras; cameras with full-frame sensors have a lot of surface area whereas cameras with the newer APS-C sensors have smaller surface areas. Sensor size is an important factor when it comes to selecting a camera to use, since it directly impacts the quality of your photos (and thus, your creative expression).
How to Add Depth of Field to Your Photos
The best way to learn how to get depth of field is to play with your camera’s settings and take different shots. Here’s how to figure out depth of field on a DSLR and on an iPhone.
1) Find something to photograph (any small object will work just fine) and put it pretty close to your camera.
2) Put your camera in Aperture Priority mode, open up your aperture as wide as possible (ideally f/2.8 or wider), and focus on the object.
3) Take a picture, then close your aperture down a bit more (say, f5.6) and shoot another photo. Lastly, close your aperture down even further (say, f16) and take one more photo.
4) Now look at all three photos and you’ll see how with a smaller aperture (higher number f-stop) you get more of the photo in focus.
Starting with iPhone 7 Plus and iOS 10.1, any iPhone with a dual camera can take photos with depth of field similar to a DSLR.
1) Open your Camera app.
2) Swipe to “Portrait Mode.”
3) Lock in your subject.
4) Follow any directions on the screen.
5) Once the “depth effect” sign appears, lock in your focus on your subject again. Adjust the brightness to your desired effect, then hit the shutter.
6) Be sure to keep your iPhone steady when using this mode (or consider using a tripod), as the process takes a little longer than a regular photo. If you phone moves, the resulting image may be blurry.
Understanding the Circle of Confusion
The circle of confusion is an important element when you’re determining depth of field. In photography, the circle of confusion refers to the aperture values in which your lens is able to focus. The circle of confusion is also the degree of tolerance that the human eye has before it distinguishes between an out of focus object and an in focus object. In other words, while an image may not actually be perfectly in focus, it appears in focus because the human eye can’t actually distinguish between something that is slightly out of focus and something that is perfectly in focus.
Bokeh photography demonstrates the most obvious example of the circle of confusion in action (see below for an example of a bokeh photo).
Macro photography is when you take photos of very small things in a larger-than-life size. So, for example, a large photo of an insect. In macro photography, you’re going to use a very shallow depth of field. Try an aperture of f/2.8, f/4 or f/5.6. You’ll also want to your camera-subject distance to be very small. You’ll also want a longer focal length and for your focus point to be very close to your camera.
A large or deep depth of field will put a longer distance into focus. Landscape photography is a good example of large or deep depth of field. In order to achieve a large or deep depth of field, you want a smaller aperture, which means the larger F-stops, i.e. a maximum aperture of f/22. Additionally, you’ll need a shorter focal length and to be further away from your subject.
A shallow depth of field is good for focusing on an option that closer to your camera. For example, a close up of bee hovering over a flower would require a shallow depth of field. In order to achieve a shallow depth of field, you want a large aperture, which means the smaller F-stops, i.e. f/2.8. Go with a longer focal length and stand relatively close to your subject.
Because landscapes have a very large depth of field — you want basically everything to be in focus — you want a smaller aperture. As you know, that means larger F-stops. Try f/22 and adjust from there. You’ll need a shorter focal length and to be far away from your subject.
Bokeh is one popular photography method that utilizes depth of field. When shooting bokeh, set your lens to the lowest aperture.