• Physical size of the transparent image on the slide
• Focal length of the lens tube used with the TIPA
• Distance from the lighting fixture to the projection surface
In most situations, using a larger source image and narrower angle lens achieves the best results.
To properly size your slide image, you can project a black 1/8" grid using the TIPA. This will show you how large the original image will need to be in order to fill the projection surface. If you see 16 squares across and 12 squares down, your image should be 2" by 1 1/2" to fill the surface.
You can also use the grid to correct distortion that may result when projecting at angles other than 90° to the projection surface.
To give you an idea of how a transparency sizing is affected by the beam spread of the lens, a 2" x 2" slide projected onto a surface 20 feet away produces the following results:
• 36° lens = 7' 6" image
• 26° lens = 5' 6" image
• 19° lens = 3' 10" image
• 10° lens = 2' image
• 5° lens = 1' 4" image