D-Link DCS-7510 User Manual page 12

Section 1 - Product Overview
Focus and Zoom Adjustment
The focus and zoom controls are located on the outside of
the camera case for easy adjustments. Use the screwdriver
provided to adjust the focus and zoom of your camera.
Note: With a shorter focal length you will get a wider field
of view, whereas a longer focal length narrows the field of
view and allows you to zoom in more on an area.
D-Link DCS-7510 User Manual 12