How Digital Photography Works

(^50) PART 2 HOW DIGITAL CAMERAS CAPTURE IMAGES
How Viewfinders Frame
Your Pictures
Using the viewfinder on a camera is so instinctive that we hardly give it a thought. It’s liter-
ally point and shoot. Earlier photographers didn’t have such an easy time of it. To see
what their cameras saw, the photographers had to drape heavy black cloths over their
cameras and their own heads. This was to shut out surrounding light so they could see
the dim image the lens projected on a sheet of ground glass at the back of the
bulky camera. The glass is etched so the light doesn’t just pass through invisibly. The
roughness makes the light’s image visible the way dirty film on a windshield picks up the
light from oncoming headlights. Ground glass is still used in cameras today, but you can
leave the black cloth at home.
In less expensive cameras,
the viewfinder is a simple
hole through the cam-
era’s case with a plastic
lens to make the scene
framed in the camera approximate
what the photograph will contain.
Because the viewfinder is not in a direct line with
the camera’s lens, the viewfinder actually frames
a scene a bit to the left and above the photo-
graph frame. The error is calledparallax. The
effect is more noticeable the closer the subject is
to the camera.
2
The viewfinder compensates for par-
allax error by including lines along
the upper and left sides of the frame
to give the photographer a general
idea of what parallax crops out of
the picture.
3
1