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Medical Forum / General / Vision / February 2005Tinted glasses?
Is it possible to buy normal glasses which are tinted on the outside but provide a clear image for the wearer? what are these types of glasses called? cheers > Is it possible to buy normal glasses which are tinted on the outside but > provide a clear image for the wearer? > > what are these types of glasses called? > > cheers You can buy Transitions lenses (in various materials and indexes) that get darker when outside in bright sunlight, but they are never perfectly clear indoors (you will loose about 10% transmittance indoors).Whether they are "clear enough" for you depends on your tolerance. The amount of darkening also depends on the temperature and the color (grey, brown, etc). Obviously, these lenses can also be affected somewhat by indoor lighting. Transitions is a brand name technology that has licensed to many lens manufactures. Another brand name is called PhotoGray for glass lenses. Here are some representative numbers on Luminous Transmittance of Photochromic Products from Sola. The first percentage is Unactivated Transmittance (indoors), and second number is Activated Transmittance (outdoors): Hard Resin (1.50 index) Transitions Gray 89% 15% 73 Degrees F Hard Resin (1.50 index) Transitions Brown 89% 17% 73 Degrees F Polycarbonate Transitions Gray 87% 22% 73 Degrees F Spectralite Velocity Transitions 87% 17% 75 Degrees F PhotoGray Extra 85% 22% 77 Degrees F 2.0mm thick Chem tempered >>Is it possible to buy normal glasses which are tinted on the outside but >>provide a clear image for the wearer? [quoted text clipped - 4 lines] > > You can buy Transitions lenses <snip> I thought the OP was asking about something different, i.e. a lens that looks untinted looking out from the wearer's POV, but looks tinted to others looking at the wearer. The short answer is no you can't, but the closest you would get would be a mirror coating. Dom > I thought the OP was asking about something different, i.e. a lens that > looks untinted looking out from the wearer's POV, but looks tinted to > others looking at the wearer. The short answer is no you can't, but the > closest you would get would be a mirror coating. > > Dom I will have to admit that I didn't know for sure what the OP was talking about. The terms were not exactly precise. >> Is it possible to buy normal glasses which are tinted on the outside but >> provide a clear image for the wearer? [quoted text clipped - 10 lines] > Obviously, > these lenses can also be affected somewhat by indoor lighting. Losing around 10% transmittance is normal for perfectly clear regular CR-39 lenses!!! AR coatings drop that to the 2-3% range. Carl > Transitions is a brand name technology that has licensed to many lens > manufactures. Another brand name is called PhotoGray for glass lenses. [quoted text clipped - 10 lines] > Spectralite Velocity Transitions 87% 17% 75 Degrees F > PhotoGray Extra 85% 22% 77 Degrees F 2.0mm thick Chem tempered "Sibirer" <seezoiter(phonetically)@mtaonline.net> wrote in message > Losing around 10% transmittance is normal for perfectly clear regular CR-39 > lenses!!! AR coatings drop that to the 2-3% range. > > Carl I presume that the numbers published by Sola on transmittance that I quoted (for regular lenses or Transition lenses) do not include loss from reflections that can be reduced by AR coating. I don't believe that the transmittance loss of non-AR coated lens is static. It depends quite a lot on the nature of the ambient light. |
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