Film-Tech Forum ARCHIVE: Light path alignment question.

This is topic Light path alignment question. in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=008268

Posted by Alan Gouger (Member # 543) on 09-22-2006, 11:24 AM:

Running a film on my Devry last night I noticed the light from the image coming through the gate was hitting the lens on the extreme bottom right corner yet everything looks fine on the screen.
Im guessing this to be due to the alignment of my light source but should the image be centered on the lens for optimal focus or is a little off center expected and not worth the effort to center it in hopes to gain yet a sharper image. In my case it is really to the edge of the lens. Im surprised its exiting the other end with no cut off.

Thanks.

Posted by Adam Martin (Member # 641) on 09-23-2006, 04:21 PM:

Lenses can be moved around in front of the beam of light to correct off-center projection (the projector is not centered to the screen). This is called lens shift and is usually a left/right adjustment to reduce keystoning.

Some lens collars and turrets have mechanical lens shift adjustments; otherwise you have to use a shim.

In your case, if you were to re-center the lens to the light beam, you would find that you would have to move and/or re-aim the projector to hit the screen properly.