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Question about Cutting Polarized lenses

cacatman

No one knows 'cacat' like cacatman!!
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I understand that one must maintain the correct "orientation" when cutting polarized lenses to size.

Can someone (like @Chris A Hardaway, @jdd32 or @kronin323) please explain why it's a problem if the Donor lens is NOT cut at the correct "angle" as the donor lens.

If BOTH left and right lenses are cut at the exact same angle, would it not just reduce the polarisation of the finished lenses equally?

And when you do explain it, can you speak in "layman's" terms. It's been over 30 years since I last went over "waves" from physics!!!!!

P.S. Sorry about the very clumsy question. I hope you can understand what I'm trying to ask.
 
I understand that one must maintain the correct "orientation" when cutting polarized lenses to size.

Can someone (like @Chris A Hardaway, @jdd32 or @kronin323) please explain why it's a problem if the Donor lens is NOT cut at the correct "angle" as the donor lens.

If BOTH left and right lenses are cut at the exact same angle, would it not just reduce the polarisation of the finished lenses equally?

And when you do explain it, can you speak in "layman's" terms. It's been over 30 years since I last went over "waves" from physics!!!!!

P.S. Sorry about the very clumsy question. I hope you can understand what I'm trying to ask.

Polarized filters work on a very specific orientation aligned in such a way to cut out glare from reflected surfaces especially on the ground (eg wet roads, car windscreen etc). When both donor lenses are tilted off-axis by say 90 degrees, the result lens effectively results in a polarized filter that's 90 degrees off in rotation. This means when it was supposed to filter out glare from the ground would no longer be able to perform that function because the filters are in a wrong alignment. In simple terms, your polarized lenses aren't doing its job and you may as well save some cash and get non polarized lenses.

The 2nd problem with misaligned polar filter is when left and right lens are relatively misaligned and out of sync. Eg. Left donor rotate left 45 degrees, right lens rotate right 45 degrees. In this case at certain angles one lens will cut out glare whereas the other would not. The person wearing this dodgy cut set will get headaches and migraine due to 3D glasses effect as one eye is seeing a completely different picture compared to the right eye: 1 with glare and 1 without.

This is why polarized lenses must be correctly aligned before cut, as a simple misalignment of 10 degrees rotation can cause noticeable problems to the wearer.

FYI all polar lenses that I cut are laser aligned and fully tested prior shipping.
 
I understand that one must maintain the correct "orientation" when cutting polarized lenses to size.

Can someone (like @Chris A Hardaway, @jdd32 or @kronin323) please explain why it's a problem if the Donor lens is NOT cut at the correct "angle" as the donor lens.

If BOTH left and right lenses are cut at the exact same angle, would it not just reduce the polarisation of the finished lenses equally?

And when you do explain it, can you speak in "layman's" terms. It's been over 30 years since I last went over "waves" from physics!!!!!

P.S. Sorry about the very clumsy question. I hope you can understand what I'm trying to ask.
A polarized filter is almost like shutter louvers, for obvious reasons, they work bes at a certain angle.
 
@jdd32 nailed it. If the two lenses aren't aligned on the same axis the two eyes are seeing two different images. This is very confusing and uncomfortable for your brain (eyes are basically an extension of the brain).

If they were both rotated slightly the same way (both 10 degrees counter clockwise) your eyes would actually feel fine. I think this is what you asked about @cacatman ? However, if they are slightly off that same way to each eye the glare won't be properly blocked.

If they were 90° off you'd be blocking glare off walls!? Useless as the sun is in the sky, casting it's light from a "mostly" vertical direction.
 
Trust the guys using proper optics equipment and w/ proper training to cut lenses. If you're cutting lenses in your garage with a dremel you're doing it wrong =)

@scienergy @jdd32 @Chris A Hardaway are the ones I know best.
Thanks @scienergy. But I wasn't asking because I wanted to do it myself with a dremel. That would be just asking for trouble. I was asking because I know that some longer lenses can be accommodated in taller donor lenses (even if the width is less) as long as rotation is acceptable. I know this can be done for non-polarised lenses. I just wasn't sure if it could be accomplished by rotating both the L and R lenses equally on each donor lens.

@jdd32 nailed it. If the two lenses aren't aligned on the same axis the two eyes are seeing two different images. This is very confusing and uncomfortable for your brain (eyes are basically an extension of the brain).

If they were both rotated slightly the same way (both 10 degrees counter clockwise) your eyes would actually feel fine. I think this is what you asked about @cacatman ? However, if they are slightly off that same way to each eye the glare won't be properly blocked.

If they were 90° off you'd be blocking glare off walls!? Useless as the sun is in the sky, casting it's light from a "mostly" vertical direction.
Thanks @jdd32, @OakleyGuru379 and thanks @Chris A Hardaway. Yes. Your "10 degrees counter clockwise" answer exactly answered my clumsy question.
 
What about these lenses that are cut to keep etching?
Should not lenses be cut so that you use visual center as a reference point?
On donor lenses, they use the lower corners and cut away the rest.
I expect that you are out of the center axis, or I'm totally wrong?
 
What about these lenses that are cut to keep etching?
Should not lenses be cut so that you use visual center as a reference point?
On donor lenses, they use the lower corners and cut away the rest.
I expect that you are out of the center axis, or I'm totally wrong?
Oakley lenses don't have any yoked prism or vertical prism that I can measure. So moving a lens up or down won't affect the optics... If they were RX lenses with "power" that would be a major issue! That's why I won't recut Rx lenses. They do have base-in prism but without power (sphere diopters) that 0.25 base in prism measures pretty steady even side to side. This means that they do have horizontal prism. I know you didn't ask this but the Polarized filter isn't affected at all moving it, only rotation is bad. I hope that helps too.
 
If they were RX moving one up/down more than the other gives double vision. If they are both moved down in RX to save an etching say, they'll give yoked prism, which means the ground will slant! Without any power "Plano" lenses won't have these issues. @jdd32 would you agree?
 

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