Correctly Adjusting Your TheaterScope System (ALS-201)
The TheaterScope has some basic adjustment points that, when set properly, will provide optimized geometry and focus of your image on screen. This article offers a brief description as to the use of these adjustments to achieve the best result for your installations.
The image above is a side view of the adjustment points on the lens mount clamp as it sits on the transit pole of the TheaterScope. The five screws you see above function as follows:
1. Far left – The largest Allen screw is the hinge for adjusting the ‘bowtie’ effect of the ISCO III lens.
2. 2nd Screw – there are actually two of these (both marked #2 above) and they are #4 metric. These adjust the Left and Right aim of the ISCO III lens.
3. Middle Screw (#4 metric) – This screw’s purpose is to secure the entire assembly to the stabilizing pole.
4. Far right (#4 metric) – This screw allows for the actual adjustment of the ‘bowtie’ effect.
The screws labeled #2 perform the left and right image adjustment. For best results, using only the projector’s primary lens, display a crosshatch or checkerboard pattern and mark the horizontal center of the image with non-adhesive tape on the screen border or masking at the top or bottom. Then bring the TheaterScope to the show position and use these screws to line up the horizontal center of the same test pattern with the original 16:9 marking.
Please see the illustrations below for the three results when adjusting screw # 4 ( the far right Allen screw):
Figure 1.a. This is the desired end result that allows viewable content in the scale and format it was intended.
Figure 1.b. This is the effect when the adjustment is too high.
Figure 1.c. This is the effect when the adjustment is too low
Below is a photo of a properly installed ALS-201 TheaterScope ISCO III lens in front of the projector’s primary lens.
Please note: figure 1a, 1b, and 1c show extreme exaggerations of the bowtie or pincushion effect, introduced by the ISCO III lens. In reality, the distortion is slight, approximately 1.5% of total image height. This distortion is intentional, as the ISCO III lens was designed to deliver correct geometry on a screen with a shallow curve. On a flat screen, the small pincushion distortion will be visible. This is best dealt with by matching the height of the center of the image to the height of the center of the screen. This allows the slight pincushion in the corners of the image to overshoot the screen, and be hidden by the screen frame / masking.