© 2010 George Lovelace

THe Depth-of-Field Button

This tip addresses the Depth-of-Field (DOF) Preview Button I must admit that this feature of my DSLR has not gotten the attention it deserves.

Since I have increasingly included the DOF in my workflow, my results have gotten better.

It essentially takes the guesswork out of my aperture selection as long as I know the result I want. Well how does it work?

One of the best explanations that I have read was written by Bryan Peterson, in his book, “Understanding Close-Up Photography”.

He explains why the viewfinder becomes dark (depending on the aperture, like f/16) when you press the DOF button. That is to say, a DSLR, no matter which aperture you select, you will always view things as if your lens were at a wide-open aperture. The key point is that even if you select an aperture, the camera will not stop down to that selected aperture until you press the shutter to make the exposure. This is due to the operation of the mirror, which causes a tempary “blackout” in the viewfinder as it steps down to the aperture that was set. Then as light passes through the stopped-down aperture, sharpness is increased, (based on the aperture). Therefore, the reason the viewfinder gets dark when you press the DOF button is that you have engaged the same lever that stops down the lens when the actual image is being made.

Understanding this concept of diminished light when the DOF button is pressed and how the camera works to assist you in selecting the best aperture to get the sharpness or lack of sharpness desired increased my confidence, that better results could be attained.

I hope increased use of DOF is in your future.