Re: Lenses
Altman updated the glass in their lenses at some (or several) points down the
line. Original
360Q's used "coke
bottle green" lenses, while later models use white
crown glass (I think that's what they
call it). Gmff, you may have had a mixed batch, and you might too, kef. Remove the lenses from a "bright"
ellipsoidal, and a "dim"
ellipsoidal and view them from the side. Do any of the lenses look green or blue? If so, that's your problem. The older lenses experienced lower light transmission. Do this if the problem stays with the
unit rather than 'moving' with the
lamp cap.
Les is onto something here, as indeed earlier versions of the
360Q used a soda lime glass (thus the greenish tint when viewing the
lens) while the later version employed the use of a clearer
crown glass. The
thickness of this
lens type will certainly affect the output of the
fixture, and the amount of dirt, dust, grime,
etc will exacerbate the problem. (Can I say that on this forum? Exacerbate just doesn't seem, well... proper.)
Wikipedia states in part:
http://en.wikipedia.org/wiki/Crown_glass_(optics)
Crown glass (optics) is produced from alkali-lime (RCH) silicates containing approximately 10% potassium oxide. It has low
refractive index (≈1.52) and low dispersion (with Abbe numbers around 60);
crown glass is one of the earliest low dispersion glasses...
Soda-lime glass - Wikipedia, the free encyclopedia
Soda-lime glass is prepared by melting the raw materials, such as sodium carbonate (soda), lime, dolomite, silicon dioxide (silica), aluminium oxide (alumina), and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675 °C...
Soda-lime glass is divided technically into glass used for windows, called float glass or
flat glass, and glass for containers, called container glass. Both types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition. Float glass has a higher magnesium oxide and sodium oxide content as compared to container glass, and a lower silica, calcium oxide, and aluminium oxide content.