NY Tint Law / meters

[tintmeter]

I remember talking with you a while ago when you where studying this issue. I also have done these tests with different films, and they have followed the mathematical calculations, at least with the meters we manufacture. Once again, I can't comment on other companies products. There is a slight variation low if the film is not adhered to the glass, the result of reflection at the glass/air interface. 2 layers stacked without being adhered read even lower because you now have 6 air/ glass,plastic interfaces . Once the backing is removed and the film is adhered to the glass the reading goes up appropriately as there are less air interfaces. Each surface light encounters has some reflection, about 3.6 percent for glass, a little less for acrylic( 3.0). I don't know about polyester but wouldn't be surprised if it is in that range. That is why you don't get 100% when you measure clear glass. You loose 3.6% to reflection on the front surface, pass through the glass, then loose another 3.6 percent to reflection at the rear surface, giving you a transmittance of about 93%. Stack 2 sheets of glass and you have 4 air interfaces where you loose 3.6% at each surface.

Mathematically;

(100-3.6)(100-3.6)(100-3.6)(100-3.6)=

(96.4)(96.4)(96.4)(96.4)=

=86.4%

That is why when you look at a roll of clear film, like saran wrap, you can't see the cardboard tube it is rolled on. There is to much light lost to reflection.

Same thing would happen in a camera zoom lens or binoculars. That is why they put anti reflective coatings on lens. That purple reflection you see on lens' is what the coating is not passing.

[EWF]

Tintmeter,

OK - I was not sure that was you. I know who you are now.

I follow you on the reflectivity but it raises another major variable. Several of our most popular films contain vapor coated aluminum layers, which, if separated from the "stack" would have measured VLRs in the 20%-30% range. The greatest variances I observed were when these films we used in the test.

Were you aware that certain films have highly reflective layers and what impact would that have on your calculations?

-Howard

[EWF]

Yet another point - based upon the latest information you provided:

Some vehicles now have double pane glass in them for noise attenuation, adding two more interfaces as compared to regular single pane auto glass. Are you not off by 7.2% right from the start in that case?

-Howard

[tintmeter]

I have seen the sputtered films, but by definition, if the light is reflected then it is not transmitted.

Transmitted light is Incident light, minus reflection, minus absorption. Light is either reflected, absorbed or transmitted. There is no other place for it to go.

Double pain glass will have higher reflectance than a single pane unless there is an antireflective coating.

By the way, some antireflective coatings are sputtered metal as used in some tint films.

[EWF]

So then: If the meter is calibrated using a single pane calibration plate, is it still accurate when metering double pane auto glass?

[EWF]

Dear Tintmeter,

Sir.

Here is a schematic drawing of single beam spectrophotometry, the method upon which your meter is based. Note that only a single sample is present.

In order to suit your purposes, you have altered this well accepted method by simultaneously metering multiple samples of known varying refractive indices with air gaps present between them.

I am unable to find a single other example, either in commercial use, academia or within the scientific research community where anyone else has done what you are doing, while claiming that the results are accurate, let alone good enough to stand up in a court of law.

In addition, I have a tenured professor of physics at RPI (an unimpeachable source) who is adamant that your method is flawed and is an aberration of the accepted practice of spectroscopic analysis as outlined above.

Please cite a single other example whereby this accepted method (above) has been altered in the manner which you alter it and is still considered valid.

I am directly asking you by what standards of accepted practice within the electromagnetic physics community do you claim that altering the above method below will yield a valid result?

Please reference any research materials to support your alterations of the method above.

Please cite a single other example of multiple specimen specroscopic analysis with air gaps and samples of varying refractive indices.

I still maintain that while it would be cumbersome and time consuming, the only way to correctly meter the net transmission of a glass/film combination would be to measure the transmission of each component part (using the above method) and then perform the mathematical calculations. Measuring the net glass/film transmission in the manner you do it is expedient and convenient, but it comes at the expense of accuracy.

Those of us within the window film community want to be accurate. Courts of law want to be accurate.

If you believe my conclusions are wrong, please use this forum to help us understand why.

-Howard

[EWF]

Dear Tintmeter,

I have another question:

Your competitors use different LEDs, circuitry, sensors and methods in their units.

Consider this example: A conscientious film installer seeks to obey the law and uses "Meter Brand A" in is shop. His customer leaves the shop with the belief that the film they paid for is legal. They are then pulled over by a police officer using "Meter Brand B" who writes them a ticket for being too dark.

What standardization methods, practices and guidelines exist in your industry?

Where are these published?

Are meter-to-meter variances accounted for in the tolerances?

How is this fair to consumers?

How is this fair to window tinters?

How is this fair to law enforcement?

Please tell us.

-Howard

[tintmeter]

There are no standards in the industry.

Each state decides how to enforce with all the pros and cons that infers.

I wish it was standardized. The Feds years ago had a standard, FMVS 205 , which regulates auto glass at time of manufacture. It has since been updated to harmonize country to country. I don't remember off hand the number. Ask the IWFA, they would know.

I brought this standardization issue up, to use Fed specs, with executives in your industry years ago. They where quite clear in wanting to stay away from involving the Feds as they feared that along with deciding the testing method to be used nationwide, they would set the percentage too, which has always been 70%. Remember the lawsuit the feds lost, tint installers going below 70% there by illegally modifying safety equipment,"U.S. vs Blue Sky Group" if my memory is correct, it was a long time ago. They sued the Florida installers for modifying safety equipment and lost because the law specified that car dealers and repair shops can't modify safety equipment, but tint shops are neither. Once again, check with the IWFA, they must have better memory than me. This law, improper modifying of safety equipment, is still out there I believe, check with the IWFA, they'd know for sure. Makes one wonder how auto dealerships can install film legally. You would think they would have to contract it to a private installer to stay legal and avoid the 1000$ per car fine. Someone should research this further as it could be a huge help to independent installers.

[EWF]

Tintmeter:

Your memory is good: The case was actually captioned "United States of America vs. Blue Skies, et al). I know this because my friend was a direct party in the action, which took place in the Federal District Court in Orlando Florida back in the late 1980s.

It's a very complicated issue, too much for discussion here and not relevant in all respects since the court dismissed the case.

I am glad that you are an advocate, but since there are currently no standards in your industry how should the installers, the public and law enforcement deal with this? The court in "Blue Skies" decided that the states have the right to regulate this on their own and now we know that the laws are enforced using equipment which is not subject to any industry standards.

I am sure you would like to have your meters accepted as the "standard" and I wish you luck in that pursuit, but until then what do we do? Tinters who want to follow the law are having trouble thru no fault of their own.

What do you suggest?

Again, I appreciate your willingness to engage in this fair and open forum discussion, but I must point out that you have not addressed some of my technical questions. Specifically, the fact that you have altered the method depicted in my schematic above. This might be why there are no standards in your industry - the underlying method is flawed.

This is not going to go away. The window film industry has every right to demand that this be resolved.

-Howard

[SWT]

Following this thread.....as best I can, lol.