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heavision

Sunglasses

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I was under canopy once recently and I glanced at my altimeter and it was dead. Battery, I guess? Wait, I know I charged that shit. I glanced again, same result; but then I lowered my chin and peeked over the top of my sunglasses: boom, clear altimeter reading. I raised my chin: disappeared. Lowered: reappears. Something to do with my sunglasses' polarization or something. It doesn't always happen, only when the sun is at a certain angle or clouds are doing something or whatever.

Question: as skydivers who have to read digital altimeters and need excellent visibility and clarity what type of sunglasses suit us best? Polarized? Nonpolarized? Other considerations?

Thoughts, suggestions?

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17 minutes ago, heavision said:

I was under canopy once recently and I glanced at my altimeter and it was dead. Battery, I guess? Wait, I know I charged that shit. I glanced again, same result; but then I lowered my chin and peeked over the top of my sunglasses: boom, clear altimeter reading. I raised my chin: disappeared. Lowered: reappears. Something to do with my sunglasses' polarization or something. It doesn't always happen, only when the sun is at a certain angle or clouds are doing something or whatever.

Question: as skydivers who have to read digital altimeters and need excellent visibility and clarity what type of sunglasses suit us best? Polarized? Nonpolarized? Other considerations?

Thoughts, suggestions?

You are correct that the polarization is interfering, and the solution is to get nonpolarized lenses.

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Anyone else have this problem? Polarized sunglasses filtering out the display on your altimeter? It seems like non-polarized ones have lots of draw backs. I guess it's just physics? Or are there different types of polarization?

Anyone have suggestions for polarized sunglasses that work well for skydiving---and don't filter out altimeter displays?

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1 minute ago, heavision said:

Anyone else have this problem? Polarized sunglasses filtering out the display on your altimeter? It seems like non-polarized ones have lots of draw backs. I guess it's just physics? Or are there different types of polarization?

Anyone have suggestions for polarized sunglasses that work well for skydiving---and don't filter out altimeter displays?

It's just physics. Polarization is nice because it can cut some glare, but apart from that I'm not sure what other drawbacks you'd be referring to of unpolarized.

Polarization has a rotational direction to it e.g. vertical vs. horizontal. Two polarizers (such as your sunglasses and altimeter screen) that are 90 degrees apart (one vertical, one horizontal) will block transmission of light. Rotate your altimeter 90 degrees and it may become visible. Get a different pair of glasses with a different angle of polarization and your alti will be visible at a different angle.

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On 9/16/2021 at 5:54 PM, nwt said:

It's just physics. Polarization is nice because it can cut some glare, but apart from that I'm not sure what other drawbacks you'd be referring to of unpolarized.

Polarization has a rotational direction to it e.g. vertical vs. horizontal. Two polarizers (such as your sunglasses and altimeter screen) that are 90 degrees apart (one vertical, one horizontal) will block transmission of light. Rotate your altimeter 90 degrees and it may become visible. Get a different pair of glasses with a different angle of polarization and your alti will be visible at a different angle.

Except polarized sunglasses are oriented to block light reflecting off of surfaces, which has a pronounced horizontal polarization. This is why they are better at preferentially cutting down on glare, compared to non-polarized sunglasses. I doubt they make polarized glasses that are oriented 90 degrees from the standard orientation. (I mean, who would want sunglasses that make glare worse?)

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On 9/18/2021 at 10:25 PM, Divalent said:

Except polarized sunglasses are oriented to block light reflecting off of surfaces, which has a pronounced horizontal polarization. This is why they are better at preferentially cutting down on glare, compared to non-polarized sunglasses. I doubt they make polarized glasses that are oriented 90 degrees from the standard orientation. (I mean, who would want sunglasses that make glare worse?)

I didn't really mean to suggest that as a solution, just to explain how polarization works. I didn't know that most reflected light is horizontally polarized though so thanks for explaining.

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