Understanding Window Tint Visible Light Transmission

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Understanding Window Tint Visible Light
Transmission
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Whether for a vehicle, home or commercial
application when referring to window tint film,
one of the most important characteristics is how
much light the tint allows to pass through. In
most applications, this is important when
attempting to gauge how much security, privacy
and protection from heat and harmful UV rays a
tint offers. In automotive applications, however
it is especially critical as a number of states
have laws limiting how dark the tint can be on a
vehicles windows. As a result, window tinting
manufacturers have created a method for
calculating how much light a window tint allows
to pass through it. However, there are a few
things to consider when discussing the darkness
of a window tint.
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• Regardless of the application, all window tint
  film is measured by the materials visible light
  transmission levels (VLT).
• The VLT value is the percentage of visible
  light the tint allows through from the exterior
  of a vehicle, building or home to the interior.
  The lower the VLT percentage, the darker the tint
  is and the more outside light it blocks.
• A window tint that has a VLT value of 5
  indicates that the window film only permits 5 of
  the exterior light to pass through it, while a
  film with a 50 VLT value allows 50 of the light
  from outside to pass through.
• In addition, because window tints are also
  offered in a variety of colors when professionals
  are referring to a tint they typically identify
  it by the tints color and VLT value. For
  example, a charcoal colored tint with a VLT of 5
  is known as charcoal 5. Likewise, a green
  colored tint film with a VLT of 50 is called
  green 50.

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• While many might assume that the VLT of a
  window tint is the only factor to consider when
  calculating the final VLT of installed window
  tint, there is one additional aspect that must be
  considered.
• Every piece of glass, regardless of the
  application, blocks a certain amount of light. As
  a result, glass also has its own VLT value, which
  must be accounted for in order to determine the
  installed window tints final VLT value. For
  example, if a state law indicated that the lowest
  legal VLT value for a tinted car window was 30
  and an individual were to install a window tint
  with a 30 VLT rating, the windows final VLT
  rating would actually fall below the legal limit
  because of the windows natural VLT value.
• Because of this, window tinting professionals
  use a simple formula to calculate the installed
  window tints final VLT value
• V1 (VLT value of glass) x V2 (VLT value of tint)
  V3 (final VLT value)

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• Lets assume, for example, the legal limit for
  the window tint of a vehicle is 30 and the
  vehicles glass has a VLT value of 75. In this
  case, since we already know the VLT value of the
  window and the final VLT value we want to achieve
  we simply need to rearrange the formula to
  calculate the proper tint to install as follows
• V3 (final VLT value) V1 (VLT of glass) V2(VLT
  value of tint) 
• 0.30 (30) 0.75 (75) .40 (40)
• According to this formula, installing a window
  tint with a VLT value of 40 will result in a
  final VLT value of 30 as desired. Professional
  installers using this formula save their
  customers a significant amount of money not only
  in traffic tickets for illegally tinted windows,
  but also in the reinstallation of window tint
  which most traffic courts require when a driver
  receives a ticket for illegally tinted windows.

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