When setting up a shot, the director of photography may ask the someone to check the shot. This is most likely when the diopter will need to be adjusted. Diopters are simple meniscus lenses which are placed in front of the camera lens and reduce the minimum focusing distance of the lens.
Instructions
Systems with ground-glass, partial ground-glass or fiber-optics screens (most 16 mm or 35 mm cameras)
1. Remove the lens or open the iris diaphragm on the lens.
2. Point the camera at a bright area, like the sky or a bright wall. If viewing through a lens, throw the image out of focus as much as possible.
3. Rotate the eyepiece diopter adjustment ring (on some finders it is a push-pull) until the grains of the ground-glass are as sharp as possible.
4. Lock the setting in place if there is a device with which to do this. The diopter eyepiece is now adjusted.
Systems that have an aerial image in place of a ground-glass (many Super 8 cameras)
5. Zoom the lens out to the longest focal length.
6. Open the lens aperture wide and focus the lens at infinity.
7. Find a distant object that you can focus on and focus the eyepiece until the object is as sharp as possible.
8. Lock the adjustment and the eyepiece is adjusted.
Tags: eyepiece adjusted, possible Lock, sharp possible, sharp possible Lock