The brown paint SCREAMS Altman to me.
I think we have a winner, see 3300.pdf. Odd that none of these are in the Photometrics Handbook. The ones of these I've used in the past had a course texture black paint however.
Indeed they both made a similar fixture; again, see the thread: Allright old timers.... Much of Altman's early fixtures were copies of Century's (or copies of fixtures of Capitol Stage Lighting, which is where Charles Altman worked before founding Altman).
I believe that is actually an Altman 3300, with Colortran's name on it....Also a quick look through my photometrics book, I found a Colortran 9 degree model which looks exactly the same as the mystery light (2nd edition page 315). The only difference I see from the picture are the holes on the back of the instrument just behind the yoke.
Good explanation, JChenault. Minor correction: both Fresnel and Step lenses are pressed glass, rather than ground. Plano convex and bi-convex lenses are made of ground glass. Only the outer surfaces refract light, so theoretically removing the material in between makes no difference. The problem comes when light hits the "steps" that are perpendicular to the flat surface. On a step lens, these risers are painted black, wich leads to concentric rings visible in the beam. On a Fresnel, the flat surface is textured or stippled, to slightly diffuse the light. On the ETC SourceFour 5° and 10° ERSs, a "micro-groove plastic fresnel lens" is used as glass would be too heavy. This lens is similar to that used on the bed of an overhead projector.
Right, while many lenses are cast these days, the uber-sensitive, high accuracy lenses such as in telescopes and other super sensitive equipment might still be ground.
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