Does your "standard" gray C polar transmit about 20%?
Isn't that about the same as your "standard" CR39 "gray 3"?
Reason I'm asking is because some danged whinerdoesn't think her "glasses are dark enough".
Does your "standard" gray C polar transmit about 20%?
Isn't that about the same as your "standard" CR39 "gray 3"?
Reason I'm asking is because some danged whiner
Depending on the lens material, polarized lenses can be tinted darker. I've done it for myself and other patients. If you have any concerns contact your lab.
There is of course, the fact that a good polar filter removes more glare without the need to just be "darker" - which is actually very bad in a sun lens. There's a whole lot more going on that simple attenuation. Perfect opportunity to properly educate this patient.
Wellll....
going back to the glass days, the standard was that Grey A was 40%, Grey B was 30%, and Grey C was 20%, when surfaced to 2.2 mm thick.
Since the introduction of plastics and dying processes and the occasional idiot that thinks he knows what he's doing, I don't think there is much of a "standard", although there are certainly plenty of shade references available. In order to get a "true" transmission, you need a spectrophotometer capable of reading from 400 to 700 nm, and then finding peak transmission and average transmission.
I've found even in the glass polarized that the polarizing laminate has subtle shade differences from batch to batch, and for awhile, we were replacing lenses in pairs so that they would always match. I can see this happening in plastics if there isn't a process to catch off-shade filters.
And like huskypaul says, drop it in the grey tank for a minute or so, and see what the patient says. Maybe her previous pair was a C+ to D- in shade numbers.
What does flash mirror add? 5%? Full mirror 10%?
P.S. Thanks to the great replies so far.
Absolutely!!Originally Posted by Uilleann
Too dark and the pupil is wide open, allowing anything that isn't filtered by the lens to sneak its way into the eye.
Depends on the coating lab. I've seen anywhere from 5 to 15%.
Depends on the mirror type and density, as well as the reflex color. It can vary widely as you've rightly guessed. Bear in mind as well that certain color casts, and even the difference between a very slightly 'warm' and a very slightly 'cool' grey lens can feel rather different to the same patient in terms of their perception of light intensity. There is a large amount of personal subjectivity when dealing with the perception of a given tint...just to add to the fun of patients like this.
Grrr. It's not like she's a downhill skier or cruises the intercoastal. Just a picky type.
It's a poly polar PAL in a 55 eye fashion zyl frame (unfortunately not big, nor wrappy).
She's going to look like she joined Eric Estrada on C.H.I.P.s when I get done with her.
He's so sexy. She'll be thrilled! Will she get a custom Kawasaki bike with her purchase?
Wasn't B+L's G-15 so named because of 85% blocking with 15% transmittance?
Hey Doc! How did you get those pictures of me!!!
What a nice scientific discussion,............. when photofilter manufacturers talk about tinting, they want to know the exact nanometer they would like to reach and how to do it.
Last edited by Chris Ryser; 09-09-2013 at 06:14 PM.
Highly doubtful this pt knows or cares about nanometers - specific or otherwise. At any rate, "darker" doesn't have anything to do with this or that wavelength per se.
Iagree with you..........................however it is sad, that optical specialists never went further than that.
Rule out pathology and medications. Check for light leaking in from around the top of the frame, especially if she spends a lot of time outside in the direct sun, a walker for instance. Work the panto and wrap tilt to displace annoying reflections and to increase the light seal. Coat the lenses to reduce reflections to a very low level. This may seem counterintuitive, but demo a brown polarized lens- especially if she's older with some hazing of the lens. In these cases, it's not the quantity, but the perceived quality of light. Good luck.
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.
Gracias, Robert.
Your welcome. I'm seeing a lot of sensitivity from my clients since the last full moon. The heat isn't helping also.
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.
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