Understanding Depth of Field

With automatic focus options on most cameras, you may not notice a change in focal range for your lens. However, you may have seen pictures where the target is in sharp focus, while the background is blurred. This is done by manipulating the depth of field of your lens, and it can be very useful for all photographers, whether professional or otherwise.

Camera lenses only have one narrow plane that is completely in focus. However, because the loss of focus is relatively gradual, you may not notice the places where the image starts to blur. Because we perceive a band of clarity, this range is called the depth of field.

The depth of field is somewhat determined by the Circle of Confusion. First, photos are created when a beam of light passes through the lens and hits film or another photosensitive substance at the back of a camera. The smaller the circle of the light beam is, the more focused the image is. This circle of light is called the Circle of Confusion, and like the depth of field, it has an acceptable range of focal ability.

The size of your desired Circle of Confusion depends mainly on the quality of image that you are wanting. If you do not plan on blowing your images up over 8″ by 10,” a circle diameter of .03 millimeters is considered sufficient. However, if you are looking for greater detail or want to print the photo even larger, you may want a smaller diameter of the circle.

There are three things that affect the depth of field, which you can manipulate to make it greater or lesser. First, the subject distance away from the camera can change your perceived depth of field. The closer a target is to a camera, the smaller the depth of field will be. This shallow focal range can help you capture smaller details.

Next, the lens focal length plays a part as well. Interestingly, a lens with a shorter focal length has a greater depth of field than one with a longer length. Thus, you have a shallower depth of field when you take a picture with a lens with a long focal length from the same location as a lens with a shorter length.

Lastly, changes in aperture can change the Circle of Confusion as well. This is because the aperture is the hole in the lens that allows in light. Thus, when you have a larger opening (or smaller f-stop), you are letting in more light, which translates to a larger circle diameter. This means that you will have a greater depth of field with a smaller f-stop. On the other hand, a larger f-stop will allow you to sharpen your focal area.

Once you perfect your ability to manipulate your camera, you can take a picture that you will want to display for all to see. One great creative way to show off your photo is to have it changed into a canvas image. For more information on this process, check out YourCanvasPhotos today.

Joseph Devine