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Meter Math

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So after checking multiple windows over the past few days I'm still trying to understand this thing. However I'm pretty sure I never will fully. After tinting, stripping, and retinting I've got some interesting numbers.

First I checked the meter to insure it's accuracy. It was within one percent on both sample pieces. The particular film that I am using global high performance. The vehicle is a 2013 kia soul. So here's the numbers

Window with no film 80%

45% film out of box; 48 to 49

40% film out of box; 42 to 43

Window with 45% film; 45%

Window with 40% film; 38%

Now my state law is 35% net with a 2 to 3% variance according to local inspection stations. Going by these numbers I could buy a 35% film and apply to some vehicles. I mainly would just need to meter each window to insure that it is within legal limits.

Going off of the formula it just doesn't add up. The formula is always lower than the actual meter. So can any of you guys that have metered for years chime in and tell me your experiences?

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If everything is completely accurate and you put a 35% film over 80% glass you will always get 28%. Problem is a box that says 35% might actually be 40% then throw in a possible +/- 3% to the film and the actual roll may meter 43% which would make the tint on glass meter at 34.4%. Even after all that then your meter may be off slightly as well that would give you a different number.

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Bump.

So after checking multiple windows over the past few days I'm still trying to understand this thing. However I'm pretty sure I never will fully. After tinting, stripping, and retinting I've got some interesting numbers.

First I checked the meter to insure it's accuracy. It was within one percent on both sample pieces. The particular film that I am using global high performance. The vehicle is a 2013 kia soul. So here's the numbers

Window with no film 80%

45% film out of box; 48 to 49

40% film out of box; 42 to 43

Window with 45% film; 45%

Window with 40% film; 38%

Now my state law is 35% net with a 2 to 3% variance according to local inspection stations. Going by these numbers I could buy a 35% film and apply to some vehicles. I mainly would just need to meter each window to insure that it is within legal limits.

Going off of the formula it just doesn't add up. The formula is always lower than the actual meter. So can any of you guys that have metered for years chime in and tell me your experiences?

The formula doesn't account for how a film's color (spectrum) impacts results.

 

Back when NC passed their net 35 law I was a film sales rep for the state and it was noted how Centaur (PT) auto film would squeak by light meter devices while ATR failed even if they both had the same VLT going on the same VLT glass. Centaur was a more bluish looking smoked film.

 

Dealer in Burlington metered film from the box and marked the metered VLT on it label. He would have a minimum of five separate boxes of film of the same film product all with various VLTs. He would determine which to use by metering the glass, picking a sample thought to pass and place a small sample to the glass to gain a net reading. If it was off, he would look to another roll with either higher or lower VLT needed to pass.

 

All variables are not covered though, because you don't know battery charge strength of your meter compared to the one at the inspection station. And even then it has to be the same type meter with the same calibration variance confirmed.

Edited by smartie2shoes

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The formula doesn't account for how a film's color (spectrum) impacts results.

 

Back when NC passed their net 35 law I was a film sales rep for the state and it was noted how Centaur (PT) auto film would squeak by light meter devices while ATR failed even if they both had the same VLT going on the same VLT glass. Centaur was a more bluish looking smoked film.

 

 

Important Point from Smartie. :yeah

 

In my earlier years, fat was sufficiently-confused because color has a part to play on the VLT reading on different test meters.

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