Depth of Field preview button …

Ever wondered what that button is around the lens mount of your dSLR?

It’s not the button you press to take the lens off the camera. On most modern dSLR’s there is another button that is usually dedicated to - depth-of-field preview.

Depth of field, or DOF, is the range between areas in an image that look sharp. It’s easiest to think of it in terms of photos you are already familiar with. Landscape photos that have most of the image sharp and in focus have deep depth of field. Portraits with the subject in focus but a background blur have shallow depth of field.

The DOF preview button helps you determine what photos will look like before the image has been taken. When the button is pressed, the lens will stop down to the aperture that you have set. Then, you will be able to see a preview of what the final image will look like through the viewfinder.

Depending on your camera, the button is usually situated near the lens, where your thumb or forefinger can press it without too much effort.