Project 52: Depth of Field

I‘ve written about depth of field before, but it’s this weeks theme, so I guess it’s time for a refresher!

What is depth of field?

As you may remember, depth of field refers to the area in focus in a photograph. Using a shallow depth of field is one way you can draw attention to your photo’s subject. You can draw attention to the subject of the photo by having it be in focus while the rest of the photo is out of focus.

Factors that Affect Depth of Field

While there are other factors that affect the depth of field, the three main factors are:

1. The focal length of the lens;
2. The distance from the camera to the subject; and
3. The aperture used by the lens.

In the spirit of complete transparency, I just ran out of time this week, so I am going to refer you back to my earlier post on depth of field for a discussion on the effect of focal length and distance between camera and subject. I’ll concentrate on aperture in this post.

Aperture

If you ask an experienced photographer how to change the depth of field, and chances are he or she will tell you to change the aperture of the lens. That’s because, of all the factors, aperture is the easiest to control.

Well, I’m not sure it’s actually the easiest to control, but photographers, being human, are lazy. If you change the focal length or the distance from the camera to the subject, you’ll have to recompose your photo. You’ll probably have to move, and who wants to do that?

No, if you change your aperture, you’re changing the exposure of the image, but you can control that on your camera. No walking involved!

You may remember that the larger the aperture (which is the smaller f-stop number) the more shallow the depth of field.

Here are two photos of Charlie. The left is taken at f/5/6 and the one on the right taken at f/16. You would expect the depth of field to be more shallow in the photo taken at f/5.6. . . .

And that is exactly what happened! (I’m acting like I can break the laws of physics and it would have turned out differently!) If you examine the f/16 photo, you’ll see more detail in the blanket and the paneling behind Charlie than in the photo taken at f/5.6. That’s because the larger depth of field allows a larger area to be in focus.

Freelensing

You want a super shallow depth of field? Try freelensing. Basically, it’s using a removable lens camera, such as a DSLR, with the lens not attached to the camera body.

Note: If you do this, you expose your camera sensor to a lot more dust and dirt than with the lens attached. Freelensing, also called lens whacking, won’t hurt your camera, but it could result in you needing to clean your camera’s sensor more often.

Kim’s up next

Next in the blog circle, we have Kim Hollis with BARKography based in Charlotte, NC. I can’t wait to see her take on the topic!