3M
Multimedia Projector MP8620
Theory and Diagrams
3M 1999
4-6
4-6.
Keystone Correction
A correct projection image on the MP8620 should be
square and in focus. A projection image that is wider at
the top and has a softened focus has keystoning.
Keystoning is visible on the MP8620 when the
projection to screen angle is greater than sixteen
degrees. As the front of the projector is raised the
projection angle increases. At sixteen degrees the
projection image is still square and in focus, at nineteen
degrees keystoning can be seen.
The MP8620 is keystone corrected at a ratio of 3.9 to 1
to provide a square focused image as shown. Restated,
for every 3.9 feet of projection distance the image is
raised 1 foot. This feature allows for 80% of the
projection image to appear above the lens center with
only 20% appearing below.
