Intro to Depth of Field

by: Autumn Lockwood

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Date: Thu, 22 Jul 2010 Time: 6:24 AM - 0 comments

If you want to really learn photography then you need to learn about depth of field. This concept is critical to helping you improve the quality of your images. Here is an overview of depth of field so you'll be sure to master this concept in no time.

Depth of Field Defined

In a photograph, depth of field can be thought of as how "deep" the focus of an image goes. In more simple terms, the depth of field refers to the difference between the items in the background losing clarity compared to the subject in focus. Think of depth of field as the relationship between the focused and blurry elements of your photograph.

As an example, a flower with a blurry background and a sharply focused flower have a low depth of field while a landscape picture with everything in focus has a high depth of field. In both of these examples, simply changing the depth of field will have a major impact to what the viewer sees in your photograph.

What Influences Depth of Field?

The primary influence on the depth of field of any particular image is the length of its exposure. The longer your camera's digital sensor or film has to absorb the image you're shooting, the more detail your camera will produce. Longer exposures will always result in greater depth of field, even if at unperceivable levels.

When it comes to changing depth of field, you can control it by increasing or decreasing the exposure time. You can do this by changing the shutter speed of your camera; slow speeds (60 and lower) will cause longer exposures and greater depth, while fast speeds (125 and higher) will decrease exposure times and cause the opposite.

How to Control Depth of Field

You can purposefully force greater depth of field into an image, however this will require manually adjusting the aperture settings of your camera. Because a longer shutter speed is required to add depth of field, less light must be allowed to enter through the lens. If you increase your exposure but forget to close down your camera aperture, you'll end up with images that are over exposed.

Changing the aperture involves moving the f-stop (often the ring around the lens behind the focus ring) to whatever number lets in the best amount of light. Any new camera will let you pick a shutter speed and then will automatically adjust the f stop, but with older cameras, you'll have to play around with the light meter until the shutter speed syncs with the right aperture setting.

Helpful Tip: If you're working with high depth of field images it's likely that you'll be working with very long exposure times (depending upon the quality of your light). Shots of this nature will almost always require a tripod to prevent blurring from camera-shake.

In every picture you take, you should consider using depth of field as it's a powerful tool in your photographer's toolbox. Objects in a photograph all lend themselves to the story that image is trying to tell - what is and isn't in focus can mean quite a lot to the relationships between those objects. Consider how you could use depth of field to impact what you can say about your subjects as this will help make your images more powerful and interesting.