Pyrex vs Lexan: Myth vs Reality?

[brightnorm]

I read somewhere in CPF that pyrex allows the transmission of 10% more light than Lexan. I've searched and can't find any clear information. Is this really accurate, and what percent of that 10% is in the visible light spectrum? Have any controlled tests been performed to judge people's subjective impressions of the difference? I know that technical specs don't always directly correlate with human perception, and assuming it really is a visible 10%, is that significant?

Brightnorm

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[K-T]

When I was searching for someone who could make some AR-coated pyrex lenses on his spec-sheets it said that 98% of the light would go thought and would not be reflected.
I don't know how that number is with lexan lenses.
Can anybody confirm something like that?
Klaus.

 

[lightlover]

According to PK, the transmissivity levels are:

Lexan = 88%
Pyrex = 95% (with the A-R coating)

I believe that the practical limit for "glass" is about 97%.

Ref: http://www.pk-engineering.com/spec.html

lightlover

 

[hairydogs]

how much in the visible spectrum?

 

[lightlover]

Ummm, well.
There's more detail at the link itself, with wavelength curves.

I've taken those readings as an indication of the visible difference.

Incidentally, the percentage difference between 88 and 95 is about +8%.

lightlover

 

[lightlover]

Brightnorm,

I was wrong about there being a curve for the Lexan.

lightlover

 

[brightnorm]

I'm sure somebody out there knows the answer; I hope they're reading this, because it could influence the purchasing decisions of some (many?) of us.

Also, we like to know stuff!

Brightnorm

 

[rigormootis]

I chose pyrex over lexan for 3 reasons...

1) better heat resistance
2) more waterproof (not the material itself, but the way it is installed vs. lexan lenses in SF lights)
3) scratch resistance.

I guess more light is good too...

 

[Dennis]

Not exactly on topic, but...

I actually prefer Lexan for duty/work lights, especially large lensed ones like the M6. Reason being that Lexan will not break when dropped. We buy the M2/M4/M6 for the shock resistant bezel, but if the glass breaks then what's the point? I have dropped my Lexan M6 from 6' onto concrete slab with no issues, it landed on one of the edges of the bezel. It has also rolled and skipped around on asphault and other surfaces with no problems. Yes, I know the Pyrex is pretty tough, but not as tough as Lexan. As far as heat resistance, the M2/M4/M6 is not meant to be on for long periods. And I think that anything that can fry a Lexan Lens, will fry your Lamp and Reflector as well.

Of course, I have had no issues with my Pyrex M2 or C2 so maybe I'm just being picky. However, having guaranteed light is more important to me than 7% extra light transmission or supposed heat resistance.

Question: All my weaponlights have Lexan. Do any of the newest ones come with Pyrex?

 

[brightnorm]

I just checked the PK's site. All it says re Lexan is 88% light transmission without stating what % of that is in the visible spectrum. I don't have the expertise to interpret the wavelength chart for coated Pyrex. At any rate there is no camparative wavelength chart between Pyrex and Lexan.

Brightnorm