KODASLIDE STEREO VIEWERS Page 22
One common problem in stereo viewers is the illumination gradient caused by the varying distances of the light bulb from the reflector (Fig. 18). The light is brighter at the center, close to the light bulb, and dimmer towards the ends, which are located further away from the light bulb. This is an inherent problem in many viewers, but the degree of the problem depends on the quality of the reflector and the geometry of the lamp interior. If the light bulb was positioned at the center of a circular reflector then this would not be a problem, but that's not usually the case. One solution to minimize this effect is to paint the lamp interior only towards the edges and not at the center.
Personally, I am an advocate of painted lamp interiors. Painting the interior of the lamp compartment white, increases secondary reflections and results in brighter and more even illumination. Fig. 19 shows a Kodaslide viewer with the lamp interior painted white (top, bottom and side surfaces). An alternative to painting is gluing reflectors in the unpainted areas.
The improvement obtained from painting the lamp interior depends on many factors like the geometry of the lamp compartment, the percentage area of the surrounding surfaces that is unpainted, the size and shape of the reflector, etc. While in certain viewers (the Realist red-button is a good example) such painting will make a big difference, in the case of the Kodaslide viewer it is not as helpful. Instead of painting the entire lamp compartment on option is to paint only the edges of the interior to minimize the illumination gradient.
Copyright ©1995 - G. A. Themelis. Reproduced with the permission of G. A. Themelis.
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