There are several reasons for the poor quality of the image:
Horizontal stripes caused by the plastic diffusing material used in place of ground glass;
Camera had difficulty focusing on the plane of the disc, focussed on the diffusing material instead;
The timing of the camera shutter caused one scan line to be blanked completely (vertical black line near left edge) - of course, where this occurred in the picture was uncontrollable and random on each shot. Using a longer shutter speed resulted in double images as the disk timing drifted between frames.
Lack of servo control meant that speed and framing was adjusted manually with the motor power supply. This is extremely touchy and will not stay in adjustment for more than a second or so. Consider that the line rate is 400 Hz, so an error of 1/4% results in the frame slipping at a rate of once per second. As a result, I had to select this picture out of 90 I took, most of which had some terrible misframing or complete loss of sync.
Despite the difficulties, the image does illustrate the quality of the disk in terms of uniform line spacing and uniform brightness of the lines.
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