NY Tint Law / meters

[TintDude]

So one of your meters could read 73 and the other could read 77 and the law enforcement officer doesn't know which end of the spectrum his meter is reading and must assume an addition variance of his meter to another +/- 2. So that makes the equation 71 to 79. Lets start with a more realistic reading since no cop is going to be measuring a window around 70% (completely un-tinted), lets go for 20%. Your meters could read anywhere between 18% and 22%. The cop measures a 20% window, reads 18% assumes his meter has a 2% variance and thinks it's reading high and the thinks window is probably 16% when it's really 20 to 22%.

As a percentage of VLT, that is a 35% error margin.

[tintmeter]

Sorry TD, I'm a bit lost on your interpretation. of the spec.

Given that the window, measured on a precision spectrophotometer, is 20.0%;

The tint meter reads 18%, within the specified +- 2% point spec.

or the tint meter reads 22%, still within the +- 2% point spec.

I don't see the issue. This has been the way windows have been measured for the last 20 years.

This is precisely why I say don't try to cut it to close, meters do vary.

Add to that spot to spot variation in the glass itself. As the human eye can just discern 3% variation when it is an abrupt change, glass manufacturers try to hold within that tolerance or better but necessarily tighter. To make thinks more interesting, tint film made by some manufacturers vary by as much as 5% spot to spot, and then there is the adhesive which can vary in thickness after installation. As an add-on after market product, law enforcement doesn't seem to be interested in the manufacturing and installation difficulties.

[TintDude]

You miss the point...

The tint meter reads 18%, within the specified +- 2% point spec.

or the tint meter reads 22%, still within the +- 2% point spec.

The cop must assume his meter is 2% off, his meter reads 18% he must assume another 2% on top of that because he doesn't know if his meter is reading on the high side or the low side. He reads 18 and assumes it may be 2% lower and that it's 16% when it's really 20%

the difference between 16% and 20% VLT is only an accuracy of 80% My math was a little off from 35% seems its 20% so +/- 10%. I guess it depends what you mean by +/- 2% ...2% of what?

[tintmeter]

I think I get were you are going.

The law is 20%, no variations allowed.

The window is technically 20.0% via precision measurement in a laboratory

The cops meter reads 18%, lowest possible by spec

The cops opinion, from his perspective, is it's between 16% and 20%

he can't write a ticket because it could be 20%, which would be legal

[TintDude]

So you are with me, glad I wasn't going down the wrong path So the real world accuracy really is +/- 10% on a supposed 20% VLT net film/glass.

Still curious what the 2% is. Is that 2% VLT or 2% of the measurement (a much smaller number)?

[Tint Wife]

TD you should rename this thread, I almost didn't look at it. I'm glad that I did lots of good info on meters here

[TintDude]

TD you should rename this thread, I almost didn't look at it. I'm glad that I did lots of good info on meters here

Done

[EWF]

Hi Tintmeter,

Whether the readings are done with one of your hand held units, or in the laboratory with a $5,000 spectrophotometer, the process of simultaneously measuring multiple substrates of varying refractive indexes is entirely dependent on the absence of even the slightest trace of air between them.

In the case of glass/film applications - there is always a small volume of air present. Hence, the problem is not with your units or their more expensive counterparts but with your method.

You have sold a very large number of them - good for you. The time has now come for the "light to be shined" on this issue. "Net Metering" is at an inaccurate science. By contrast, states which have film laws (laws that regulate the applied film as opposed to the glass/film combination) are scientifically sound.

This forum is a fair and open exchange. If you believe you are correct - address the following scientific argument with specificity:

Your method relies entirely upon the absolute absence of any air gap whatsoever.

This condition is never met when it comes to glass/film combinations

The polyester, glass, metals and other components have varying refractive indexes with small air gaps

Again, it matters not what equipment is used. Simultaneous "Net Metering" is only accurate in the absence of any air gaps.

-Howard

[tintmeter]

TD, it is plus or minus 2 percentage points of the reading, not 2% of the total reading. Think of reading a thermometer, same idea

Howard, I can not speak to the different manufacturing processes involved in aftermarket film and the effects that process may have on net metering.

I would love some verifiable scientific data about how much these factors might change the reading, either up or down. Is it a huge variation or minimal? The issue you might face in court with this line of thought is that this is "After market" film. No one was forced to install the film. This goes to a manufacturing issue of the "after market" film, similar to the MFGers that can't hold spot to spot tolerances in dyeing( Ive seen +-5% point variation on some films). If you think net metering of the film and glass together is unfair, I suggest getting the IWFA to lobby to change the laws. If in your opinion you can't measure the film glass combo together after installation, how do you propose enforcing the law? Don't think custy's are going to appreciate the cop peeling the film to test it by itself.

[EWF]

Hi Tintmeter,

First, I wish to sincerely thank you for your willingness to discuss this in an open forum such as this.

I suppose I should tell you what led me along this path in the first place:

We receive a steady stream of calls from installing dealers and retail customers about variances in meter readings and tickets that are written for film which is just over the legal limit. In the course of doing business, we dispense advice in this field. As such, I want to be sure that we are always providing accurate guidance.

I spent time with the various meters we have in our warehouses. During the course of my investigation, I found that if I inserted 50% film into a film-only meter, it correctly read 50%. If I then doubled up the film, I would get a reading of 50% of 50% (or 25%) which made perfect sense.

I then used several meters to measure glass alone. The meters were in general agreement and the results seemed fine.

Then, I started to measure glass/film combinations and the mathmatics no longer worked. If (for example) I put 42% film on 70% glass, I expected a reading of 42% of 70% ( 29.4 % thereabout). I did not. In fact, various glass/film combinations were producing mathematical results of +/- 11%.

I could not understand this result.

In my quest to figure this out, I consulted with a professor of physics at RPI. He determined that my methodology was flawed because metering these substrates simultaneously required that there be no air gap whatsoever between them. I explained about the adhesive and that whatever air gap was present, had to be minimal. His response was quite interesting. As an example, he cited sunscreen lotions which are applied to the skin leave extremely thin coatings yet can block a significant amount of UV light. Using this example, he wanted me to understand that any air gap (no matter how thin) rendered the method invalid. Only in such cases where the absolute absence of an air gap was assured could the meter reading be relied upon.

My next question was then; If the reading is incorrect - by how much? He response was that there was no way to tell. From a purely scientific perspective, he claims that the reading is incorrect and that too many variables are in play to answer my question.

This is my position:

Since you market these meters and they are used as a primary reference both by installers and in courts of law, I think it is incumbent upon you to investigate and be forthcoming in regard to the limitations and vulnerabilities inherent in your metering methodology. Neither I or the IWFA has the resources to change the law.

You make a valid point about the alternative method of metering the film only as this is a "destructive test". Still, if people are going to be subject to law enforcement action, be adjudicated by trial and suffer the penalties, they have every right to demand that all information about the evidence against them be clarified.

In response to the question you ask "is it huge or is it minimal?" I do not know, but I am calling upon you to investigate this and publish your findings. I understand that this question may not have been raised in the past, but now that it has - in the interest of fairness and justice, I believe you owe us an answer.

-Howard