Chief Blur Buster wrote:The theory of contrast ratio amplification by two layers of LCD is mathematically sound. (1/1000th of 1/1000th) versus (1000/1000th of 1000/1000th) is a 1000000:1 ratio.
for each wavelength of light, yes, but the perceived brightness depends on a weighted spectrum
suppose layer 1, turned all the way to "black", transmits blue light 100% and red/green 0%.
suppose layer 2 does exactly the same thing. then stacking the two doesn't make "black" any darker.
or suppose layer 2, turned all the way to "black", transmits red light 100% and blue/green 0%. then stacking the two gives a completely dark black.
of course this isn't talking very precisely since light doesn't just divide into red/green/blue. similarly, there's the issue of polarization.
in equations, ignoring polarization:
if the backlight has the spectrum B(x)
layer 1 has the transmittance function T1(x)
layer 2 has the transmittance function T2(x)
and the luminosity function (https://en.wikipedia.org/wiki/Luminosity_function
) is V(x)
the luminosity using only layer 1 is
integral dx V(x) T1(x) B(x)
the luminosity using both layers is
integral dx V(x) T1(x) T2(x) B(x)