NY Tint Law / meters

[EWF]

Questions for Tintmeter:

Thanks for the clarification. In regard to that 1%, is that higher or lower if the vehicle glass is thicker than the calibration plate?

Also:

The meters measure the glass, film and adhesive simultaneously. The polyester film has a different refractive index than the glass. Between the polyester and the glass is a layer of adhesive, so the glass and film are separated.

According to a renowned physics professor I consulted, under these circumstances a precise reading can not be obtained using the method employed by these meters. Note that the calibration plates are glass only - not glass/film combinations.

What is your response to this?

-Howard

[EWF]

Additional Questions For Tintmeter:

Window films can vary in thickness, visible reflectivity, color pigmentation and adhesive thickness. In fact, our company sells over 100 different constructions.

Because the meters are measuring glass + film (with a space in between) please explain how the meters adapt themselves to the wide range of possible combinations.

-Howard

[tintmeter]

I guess I didn't state it clearly, the effect of refractance is to raise the reading because it shortens the effective beam length.

The thickness is insignificant.

It is true that the meter is measuring the glass and the polyester together, both refractances are close enough to have the same effect. The adhesive layer eliminates the air gap(unless it's one of those 99$ bubble installs!! HeHe) Thus there are only 2 air interfaces, similar to lens' glued together with cement.

I suspect your physics professor may be miss-understanding what measurement process is being used, as this is identical to single beam spectrophotometer, a machine with a 100 year history. The use of a spectrophotometer, which is readily available in crime labs and universities, is what some courts have used when people contest the reading.

[EWF]

Hi Tintmeter,

As it was explained to me, the method used by the meter is adequate for measuring transmission of a single specimen or two specimens of similar refractive indexes joined without a gap. In this case, the refractive index of glass is (approx) 1.5. The refractive index of the base polyester is 1.67. Add to the list of variables the different metals which are used in our films, including (but not limited to) aluminum, silver, nichrome, copper, gold among others which are often deposited in layers. While the glass remains constant, films of varying thickness containing any combination of these metals would (I am told) have refractive indexes greater than 1.67, increasing the spread further still

Can you please explain, with specificity:

How much will the accuracy of the meter reading vary given the difference between 1.5, 1.67 and perhaps 1.85? At what point does the "spread" become significant?

In addition: I know from experience that the various layers within multi-ply solar control films are not vacuum sealed. Even the smallest air gap presents problems for this metering method as you pointed out. If the films were in fact vacuum sealed, the normal drying process (which involves the transmission of moisture vapor thru the film) would not take place and the films would never dry out.

It is my belief that while these meters are OK, they are not accurate enough to be used against defendants in a court of law.

I do have another question - which I would like you to address to the thousands of installers who read these boards:

I agree with your statement that errors due to refractivity will generally increase the reading on the meter. In that case, it is misleading installers into thinking that they are installing films which are light enough to be legal, yet in fact, are not. Many of them base their supplier decisions on "hitting the legal mark" for their state. Based on the readings of these meters, many of them have made incorrect decisions and their customers have been ticketed as a result.

Also - I ask that you address standardization within your industry. More than one company supplies these meters and all use different LEDs and circuitry. I am aware of instances where installers relied upon a meter to tint a vehicle legally (or so they believed) only to have a police officer ticket a vehicle with a different brand of meter that gave a different (illegal) reading. How do your various models and iterations differ? When you came out with a new version, did you recall all the old ones and bring them in for service?

I am sure if I asked each meter manufacturer, they would state that their meter is correct. Please address this.

-Howard

[EWF]

Tintmeter,

True or False:

Your metering method relies upon the absolute absence of air between those substrates.

-Howard

[TintDude]

I am aware of instances where installers relied upon a meter to tint a vehicle legally (or so they believed) only to have a police officer ticket a vehicle with a different brand of meter that gave a different (illegal) reading. How do your various models and iterations differ?

I was thinking the same thing H. Not only with different brands meters, I'm wondering how 10 meters of the same brand would do on the same window.

[Guest Crackz]

nice big up to howard for finding a flaw in the meter and the law

[Guest Crackz]

when howard wins this case and finds the meters faulty we all should buy a roll of film to pay for the legal fees he is paying to find the meters faulty that just my opinion

[tintmeter]

I will first preface my comments and say I can not speak for other meters, their technology or accuracy.

I only understand the meter I designed 20 years ago, of which there are over 150,000 in use worldwide.

The refractive index variations do not have a significant effect on varying the beam. It may read slightly high, but within spec. If you are trying to hold within 1%, than you will have trouble as the meters are only spec'ed to + - 2 % points, ie, the meter reads "75%" means the actual reading in a precision spectrophotometer could be 73,74, 75, 76 0r 77 percent. These meters were never designed to be used to push the limit of the law. If you want accuracy of + - 0.1 % then use a spectrophotometer at 5,000$ each, not a tint meter for 79$

[tintmeter]

A question for Howard r other interested parties. We are soon to release a new meter, possibly using a white LED rather than green. It will closely track the CIE illuminant A, which is the international standard when measuring windshields. The issue is it will read about 1% lower at 70%. It will read the same as green below 50% though. I brought this up with the powers that be many years ago, and the consensus was to stay with green to read a hair higher with clearer films, but now with increased international enforcement at 70% we are being asked to use the CIE illuminant A. For most states, there will be no difference, but for places like NY, the new meter will read about 1% less then the old meters. Any opinions?