uneven polarized sunglasses

Hi folks,

I recently purchased a new pair of perscription sunglasses with
polarized lenses. (They weren't cheap ones, ether...) The
polarization on the lenses seem very uneven to me. If I look at a
clear blue sky, I can see that the lenses looks splotchy, as if the
direction of the polarization was not uniform throughout them. I see
this as well if I examine them with a polarized camera filter.

I've had polarized glasses before, and I've not noticed this, although
it's not something I explicitly looked for. This pair seems
particularly distracting - I've actually had these redone by the lab,
with similar results both times.

Before I take these back again, I'd like to know if I'm expecting too
much. More specifically:
- In general, how even should the polarization on perscription
sunglasses be?
- How much should a strongish perscription (~-5) affect the evenness of
the polarization?
- Would the fact that these are high IOR lenses affect how even a
result I can expect?

Thanks for any insight,
-p

Thanks for the response - it's very helpful. I'm aware of the effects
you mention (stress patterns on glass, etc.) and this is entirely
different. I guess they're going back again. Bleh.

Thanks again.

-p


Robert Martellaro wrote:
> On 1 Aug 2006 21:39:43 -0700, "porf67" <(E-Mail Removed)> wrote:
>
> >Hi folks,
> >
> >I recently purchased a new pair of perscription sunglasses with
> >polarized lenses. (They weren't cheap ones, ether...) The
> >polarization on the lenses seem very uneven to me. If I look at a
> >clear blue sky, I can see that the lenses looks splotchy, as if the
> >direction of the polarization was not uniform throughout them. I see
> >this as well if I examine them with a polarized camera filter.
> >
> >I've had polarized glasses before, and I've not noticed this, although
> >it's not something I explicitly looked for. This pair seems
> >particularly distracting - I've actually had these redone by the lab,
> >with similar results both times.
> >
> >Before I take these back again, I'd like to know if I'm expecting too
> >much. More specifically:
> >- In general, how even should the polarization on perscription
> >sunglasses be?
>
> You should have no awareness of the polarization except for reduced glare and
> increased contrast, with stress patterns and a puffy cloud appearance on
> tempered glass and the inability to clearly see LCD screens all being normal.
>
> >- How much should a strongish perscription (~-5) affect the evenness of
> >the polarization?
>
> None.
>
> >- Would the fact that these are high IOR lenses affect how even a
> >result I can expect?
>
> Nope.
>
> This problem is probably due to fabrication errors that are warping the lens,
> and/or a cheap/damaged full metal frame that is putting uneven stress on the
> lenses.
>
> >
> >Thanks for any insight,
> >-p
>
> Hope this helps,
>
> Robert Martellaro
> ~~~~~~~~~~~~~~~~~~
> Optician/Owner
> Roberts Optical
> ~~~~~~~~~~~~~~~~~~
> "If a million people believe a foolish thing, it is still a foolish thing."
> - Anatole France

In article <(E-Mail Removed)>,
Robert Martellaro <(E-Mail Removed)> wrote:
....
>
>>- How much should a strongish perscription (~-5) affect the evenness of
>>the polarization?
>
>None.

Not none with me!

Looking at any kind of glare via reflection shows it --
especially via tilting the head back and forth (left-right) --
HUGE and OBVIOUS difference.

Something in physics about non-porarized light, when
reflected, or maybe glancing reflection, gets polarized
at right angles to the plane of something -- was LONG ago,
that course.

And that effect is the *reason* for buying polarized
glasses, for reduced glare reflected from highway when
driving eg into setting sun.

Ditto for piercing sky-reflection when looking at angle
into eg a fishing-stream -- can see fish, bottom, etc
much clearer.

At least that's my experience -- although maybe not everyone's.

Cheers!

David