Can anyone tell me what lenses block up too 400nm?:hammer:
400nm
Can anyone tell me what lenses block up too 400nm?:hammer:
I have a book (somewhere) that shows the light transmission at various frequencies with different lens materials and tints. 100% blockage at 400nm will most likely require a tinted lens in conjunction with uv filter.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Many lenses "block up to 400nm. What percentage of blockage do you want at 400nm?
well polycarb transmits past 380nm allowing anything past 380nm to pass through. I am looking for a lens that only transmits wavelengths past 400nm giving a true 100% UV protection (not jus the standard 380nm that ANSI standards allow) I was just wondering if there are any lenses out there that meet these standards. Thanx!! :cheers: :hammer:
I believe the EU spec for sunlenses is 400nm, you may want to ask one of the Brits on the board for a manufacturer. Alternativly talk to the rep for any multinational lens manufacturer, they may be able to special order a UV400 pair for you. Be aware that you may not be able to get clear lenses, only tinted.
Once Chris Reyser finds this thread I'm sure he'll point you to his web site where he has UV400 tint available. I haven't used it so this isn't an endorsement only an observation.
Last edited by coda; 03-10-2005 at 06:52 PM.
I did find it coda, and here is an answer.Originally Posted by coda
Every lens today, since about 1980 contains UV inhibors which were added to the monomers because plastic lenses used to yellow badly within 2 years at that time. The protection usually goes from 270nm to 360nm. That much for UV B.
UV A of which the range is from 360 to 400nm can be covered by treating any lens that is treatable or tintable either bit own surface or a tintable coating.
Any UV treatment that has a clear apperance is not fully protective to 400nm it will need the yellowish tinge.
The only ready available lenses that go very close to 400nm are polycarbonates .
As coda said you can look at my website which contains a load of information about UV treatments. You can find it at http://optochemicals.com
Best regards,
OPTIDONN,
I found it.
From "Spectral Transmittance of Lens Materials" by Daniel Torgersen March 1998.
Lenses that have zero transmittance at 400nm.
CR39 PLS530
CR39 PLS540
POLYCARBONATE AEGIS GOLD, PEWTER, AND SAPPHIRE
LENSES WITH LESS THAN 5% TRANSMISSION AT 400NM
YELLOW GLASS (ABOUT 1%)
1.60 GLASS UVSG (ABOUT 1%)
CR39 YELLOW (ABOUT 3%)
CR39 BROWN (ABOUT 2%)
CR39 POLARIZED GRAY C (ABOUT4%)
CR39 POLARIZED MELANIN (ABOUT 2%)
SPECTRALITE TRANSITIONS III FADED OR DARKENED (ABOUT 3%)
POLYCARBONATE BLUEBLOCKER (LESS THAN 1%)
This is as of 1998.
Hope this helps
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
thanks Robert I think that will help quite a bit! Where did you get that book?
Optidonn,
Your welcome. It was a hand me down from a friend in the lab biz. You can get it from the OLA, the acronym Optical Laboratories Association. I suspect that there are newer editions available.
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
Question:
Does it say ZERO transmission at 400nm or does it say full absorbtion from 270nm or 360nm ..........to 400nm
If it states at 400nm only it has been measured at 400nm only which indicates only that particular wave length and not the absorbtion between 360nm and 400nm which is the most inportant matter.
You do need full UV coverage from 270nm ......................to 400nm at every wave length in between. A UV meter in a store will NOT provide you that answer.
Do you honestly believe that anyone would claim UV400 on a lens that doesn't block shorter wavelengths as well? Come on, you know they'd be setting themselves up for the optical industry lawsuit of the century.
I know Dan Torgersen and anyone else who does certainly wouldn't be impugninghis work.
Chris,
The measurements were at five nanometers increments in the uv and visible range and fifty nanometers in the infrared. The clearer lenses have a sharp cut-off and the deeper tints are more of a gradual roll-off. For example the graph for cr39 polarized gray c shows transmission starting at 390nm rising to 4% at 400nm, 18% at 420nm and stays relatively flat through 660 nm with a gentile rise to 40% at 780nm.
Respectively
Science is a way of trying not to fool yourself. - Richard P. Feynman
Experience is the hardest teacher. She gives the test before the lesson.
I would not know about claims of UV on the lens, but I do know some products on the market that claim protection at 400nm and they dont.
Whats the big fuss ........... all I asked a question which is a valid question. You got the book. so look it up.
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