Beecher's Handouts /

Depth-of-Field / 16.6 - A Reason for Poor Backgrounds

One reason for poor backgrounds, is the fact that when you're looking through your camera, the background is apt to be out-of-focus.

So, you don't pay much attention to the background.

Why is the background out-of-focus?

When you're looking through your viewfinder, the lens opening is wide open.

The lens opening stays wide open, until you press the shutter release, so you can see what you're photographing easily.

The aperture may be at f/4.5, for example.

Yet, when you press the shutter release, the lens opening may be different.

If it's a sunny day, the photograph may be taken at f/22.

So?

Because you're looking through your viewfinder with the lens wide open all of the time, you're judging the composition with the least depth-of-field.

Depending on the f/stop that's selected when the shutter release is pressed, more could be in focus in your photograph than what you saw in the viewfinder.

For example, when I was looking through my viewfinder, the photograph to the left is what I saw.

The right-hand photograph is what I got as a photograph.

Because it was a sunny day, the camera chose f/22 for the lens opening.

Therefore, far more was in focus than what I saw through the viewfinder (which is always wide open).


f/4.5	f/22
What I Saw in the Viewfinder	The Actual Photograph

Note how the background is sharper in the second photograph.

There's more depth-of-field than what I saw through he viewfinder.

That's because the camera selected f/22.

The farm and lines on the highway are much sharper due to the greater depth-of-field at f/22.

And, they're more distracting.

Solution

Many cameras have a depth-of-field preview button.

When you press the button, the lens opening moves from wide-open, say f/4.5, to where it will be when the shutter is released.

This feature is handy for judging depth-of-field.

When you press the button, the viewfinder may become quite dark.

You may not be able to see your subject clearly, but you can see the outline of the subject.

Press the button and release it, back and forth, to compare the depth-of-field.

DEP on Canon Cameras

Canon cameras have a feature called DEP which allows you to more easily adjust the aperture for more depth-of-field.

For less, use the aperture-priority exposure mode.