Looking for a progressive .... polar A

[kaypaula]

Hi all,
For myself, not a patient, I was wanting to try and Brown A polarized lens. I wear Hoya IDLS3 but I think I'm going to have to go to a different manufacturer for this lens. Anyone know of a decent prog I can get the lightest brown polar?

thanks
Paula

[Kwill212]

You should be able to get just about any spheric front freeform PAL in polar brown or grey, call your lab and see what they have.

[dima]

Yes, Iot design for sure

[lensmanmd]

Hi all,
For myself, not a patient, I was wanting to try and Brown A polarized lens. I wear Hoya IDLS3 but I think I'm going to have to go to a different manufacturer for this lens. Anyone know of a decent prog I can get the lightest brown polar?

thanks
Paula

Grey A is readily available, Brown A is a bit tougher, but KBCo may have a Brown A available. That said, FF would be limited to OEM or Essilor designs. I second IOT. Alpha45 Ultimate would be my go-to for this.

[drk]

I'm kinda dumb.

I had a bunch of really great KBCo polar samples...every color and density under the sun.

But I have a roadblock on understanding the usefulness of Polar A vs. Polar C.

Clearly, the polar C is great for sunglasses.

Polar A is ~ 50% transmission +/-. Meaning the polarization will be about 50% effective, too.

So, what's the appeal? Who want's half-dark, half polarized lenses?

Amirite or amirong?

[lensmanmd]

I'm kinda dumb.

I had a bunch of really great KBCo polar samples...every color and density under the sun.

But I have a roadblock on understanding the usefulness of Polar A vs. Polar C.

Clearly, the polar C is great for sunglasses.

Polar A is ~ 50% transmission +/-. Meaning the polarization will be about 50% effective, too.

So, what's the appeal? Who want's half-dark, half polarized lenses?

Amirite or amirong?

Hey Doc, polarization will still be 100% effective, and, yes, it will be less than half dark. There are those that want a light polarized lens, for there own reasons, just like there are those that like clear lenses with mirrors.
Personally, i can't see the reasoning, but there are personal reasons regardless. This is why Drivewear exists.

[dima]

Hey Doc, polarization will still be 100% effective, and, yes, it will be less than half dark. There are those that want a light polarized lens, for there own reasons, just like there are those that like clear lenses with mirrors.
Personally, i can't see the reasoning, but there are personal reasons regardless. This is why Drivewear exists.

+1 for Lensmanmd

if the polarized filter inside is good high efficency the polar effect will be 99% in the same polar A, B or C

[Robert Martellaro]

So, what's the appeal? Who want's half-dark, half polarized lenses?

I use the Gray A's for golfers and folks who find Gray C too dark and strongly prefer gray over brown.

A fully polarized lens can not have more than 50% transmittance. Looking at Spectral Transmission of Lens Materials (Torgersen 1998), a glass Gray 1 has ~45% transmittance. It's the yellow, blue and red polar lenses that have very low efficiencies due to their high transmittance.

Best regards,

Robert Martellaro

[drk]

OK, let's have an argument.

I thought we established that polarized filters are only as effective as they are dark. You can't absorb light without a pigment. You can't have a clear-ish polarizing filter that is "fully effective".

I thought we discussed this with the Transitions Vantage stuff.

[drk]

AHA! https://www.optiboard.com/forums/sho...itions+vantage

AHA AHA! https://www.optiboard.com/forums/sho...itions+vantage

[dima]

I use the Gray A's for golfers and folks who find Gray C too dark and strongly prefer gray over brown.

A fully polarized lens can not have more than 50% transmittance. Looking at Spectral Transmission of Lens Materials (Torgersen 1998), a glass Gray 1 has ~45% transmittance. It's the yellow, blue and red polar lenses that have very low efficiencies due to their high transmittance.

Best regards,

Robert Martellaro

True, I saw cat 2 polar glass (with trasmittance lower than 45%) have 96% of polar efficiency

[lensmanmd]

Effect on the brain’s perception, or real world? That is the question.

https://www.edmundoptics.com/knowledge-center/application-notes/optics/introduction-to-polarization/

[Kwill212]

OK, let's have an argument.

I thought we established that polarized filters are only as effective as they are dark. You can't absorb light without a pigment. You can't have a clear-ish polarizing filter that is "fully effective".

I thought we discussed this with the Transitions Vantage stuff.


AHA! https://www.optiboard.com/forums/sho...itions+vantage

AHA AHA! https://www.optiboard.com/forums/sho...itions+vantage

This is true for VANTAGE lenses. They are only as effective as they are dark. Something about the tinting process aligning the polarization media/crystals/magic particles in the lens.

An ideal fixed Polaroid filter, as would be used in sunglasses, would block at least 50% of light at 100% polarization regardless of tint. It's Malus's Law. 50% of the light would be absorbed by the filter. That's why it can't be lighter than 50%. In the real world with entropy and inefficiencies, the real world measurement would be slightly less than 50% light transmission. According to wikipedia 38%.

A Polaroid filter blocks ALL horizontal light, not just horizontally polarized reflected light. Unpolarized light is omnidirectional. Light striking a filter can be broken down into a horizontal and vertical component. Mathematically this will resolve to 50% of the incident light being absorbed by the filter. At 30 degrees 25% of the light will be absorbed, at 45 degrees 50% will be absorbed, at 60 degrees 75% will be absorbed, etc.

[drk]

Ok, this is sinking in a little, I think.

See if this is true: "For a polarized filter to be 100% effective, it only has to be about what appears to be 50% "dark" to the observer. Because it is only blocking one direction of light, not all. If you want 100% dark, you need two of them crossed 90 degrees."

I think I've got it! Thank you!

[Lensman11]

A little history for those who are interested. The Polarizing filter was invented by Dr. Edwin Land of Polaroid camera fame. That is why Polaroid is in the name of the company that made the camera. His idea was to put a polarizing filters places at 45 over the headlights on cars. The driver would wear similar filters at 45. The on coming car would have the opposing angle on the filter in glasses so it would block the headlight brightness but have no effect on the light from his car as the positioning was the same as his glasses. The glasses could not be dark as driving at night with dark glasses would not work to well. The idea was rejected by the auto industry mostly because if they didn’t develop something they weren’t interested. The filters did play a big part in WW 2 as an aid to help pilots spot submarines below the surface. Dr Land went on to develop instant photography and held hundreds of patents in optics. The filters were adopted by American Optical to make the first polarizing sunglasses.