In article <4ogvth$hme$1@mhadf.production.compuserve.com>, 73663.1572@CompuServe.COM says...

>How is a depth of field preview used? I know how to physicly use the device
>I would like to know what information I am getting and how to use it when
>taking pictures.

For me, the most important use for DOF is not the obvious (checking what is sharp or not), since that is difficult to evaluate very accurately in the
darkened finder. I use it to evaluate the "texture" of out-of-focus areas,
and select the aperture which provides the feel in the soft areas that I want. The DOF control is also useful for evaluating dark areas in the photo, and for seeing what the photo will look like with darker areas dropped to
black. It is also useful for evaluating form in the photograph, since it reduces the image to fairly broad areas of tone.
Hope This Helps