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Thread: Looking for a progressive .... polar A

  1. #1
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    Looking for a progressive .... polar A

    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
    ~Follow Your Bliss~

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    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.

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    Yes, Iot design for sure

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    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    Quote Originally Posted by kaypaula View Post
    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.
    I bend light. That is what I do.

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    What's up? drk's Avatar
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    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?

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    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    Quote Originally Posted by drk View Post
    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.
    I bend light. That is what I do.

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    Quote Originally Posted by lensmanmd View Post
    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

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    Quote Originally Posted by drk View Post
    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
    Roberts Optical Ltd.
    Wauwatosa Wi.
    www.roberts-optical.com
    ~~~~~~~~~~~~~~~~~~
    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.



  9. #9
    What's up? drk's Avatar
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    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.

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    Quote Originally Posted by Robert Martellaro View Post
    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

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    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
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    Effect on the brain’s perception, or real world? That is the question.

    https://www.edmundoptics.com/knowled...-polarization/
    I bend light. That is what I do.

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    Quote Originally Posted by drk View Post

    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.

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    What's up? drk's Avatar
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    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!

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    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.

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    Quote Originally Posted by lensmanmd View Post
    Effect on the brain’s perception, or real world? That is the question.

    https://www.edmundoptics.com/knowled...-polarization/
    Great site! Would the Committee for Hall of Fame consider this site for inclusion?

    I think it's worthy for an optical nerd better at following the math than moi.

    Which is the laser again?

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    Quote Originally Posted by drk View Post
    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!

    Not really how I would word it but it sounds right. I think I would say the maximum VLT of an perfectly polarized lens(linear polarizer) is 50%. Obviously it can be tinted darker to whatever VLT less than 50% that you want.

    You can show that it is the polarization that is causing the darkening and not a tint by a simple experiment. Take 3 polarizers align one horizontally then stack one on top of it aligned vertically. Ideally this is 100% dark right? No light passes through. What happens when you add a 3rd polarizer in front of or behind the 2 crossed polarizers? Nothing. But, what happens if you slide the 3rd polarizer in between the other 2? Spooky stuff, that's what. You will get light transmission through the set of 3 polarizers(if the middle filter is not at 90 or 0 degrees). So by adding a 3rd dark lens we have gone from zero VLT to some VLT. We have made the 3 lens set up transmit more light than the 2 lens set up. Clearly the darkening effect is not from the tint of the lens. If it were, 3 lenses would always be equal or darker than 2 lenses. The 3 polarizers paradox can be explained classically and relatively easily understood by using Malus's law. This video sums it up nicely. However you can also go way down the rabbit hole into quantum physics with the 3 polarizer paradox if that's your thing.

  18. #18
    What's up? drk's Avatar
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    "VLT" = visible light transmission.

    No, I'm trying to say it in "plainspeak". I can further, more simply-yet restate it as this: "Well duh, a 100% effective polarizer ALWAYS looks only half-dark."

    So, in answer to my original question "So, what's the appeal? Who want's half-dark, half polarized lenses?" the answer is...

    "No, drk, you have that wrong. They're half-dark, f-u-l-l-y polarized lenses."

    Then I would come back and say. "Ok. Who want's half-dark, fully polarized lenses?"

    And then I'd answer that with "Good question. Night fisherman?"

    And then I'd have a laugh with myself.

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    Well duh, a 100% effective polarizer ALWAYS looks AT LEAST half-dark(when viewing unpolarized light). I couldn't help unplain-speaking it.

    Who wants grey A? I don't know. I have only ever used them to tint over them to a different color.

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    Yes, these work great if you have a patient that wants a gradient polarized lens...just use gray A and tint any color on top. Also, work well for those with cataracts who still want polarized lenses but not very dark.....

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