Dick Roadnight , Jul 27, 2003; 06:46 p.m.
Are there any any loose elements in the lens?
Does the distortion move round if you rotate the lens?
Is the test slide absolutely flat?
Does the problem move round the screen if you re-orientate the silde?
Can you get the image in focus by moving the screen?
Do you need a lens carrier with that lens?
can you move the lens, and does it affect he image?
So... it could be:
the adjustment of the bulb position.
The positioning of the slide
The condensors - do you need special condensors for that lens?
The arrangement of the condensors
The positioning of the lens
The perpendiculararity of the screen