The liquid crystal layer controls the absorption of the backlighting and the rays that make it through the first polarized layer are polarized in one direction (assume vertically for a minute) that vertically polarized light then passes through the liquid crystal layer and depending on it's states changes polarized orientation slightly (this of the LC layer as a wave retarder) as the phase is changed these rays must then pass through the second polarized layer before reaching the watchers eye. Overlaid on the backlight is crossed polarized filters with a liquid crystal layer between the crossed polarized layers. A backlight is going to be on while the TV is on and it effects the entire screen. That's the background, now the backlighting that was mentioned in a previous post will give you a better idea of the amount of blue light being emitted. That very same persistence of vision is why a 120hz TV is better for movies or sports that have a lot of motion since the refresh rate of the entire image on the TV screen is redrawn more times in that second, going back to our flip book example the pages are flipped faster so the animation looks smooth rather than jerky. The brain perceives a dimmer bulb by flicking the LED on and off fast enough that the bulb looks dim, which allows a digital processor to control the working of the TV. The human eye has a thing called persistence of vision, think of a flip book where the same image is presented slightly different on each page of a book by flipping through the pages of the book you can attain the effect of motion. In essence now you have created a scenario where the state can be on for 50% of a second, creating the illusion of a half dim bulb, in reality the bulb is light full on for 1/2 a second and full off for 1/2 a second. Lets say for simplicity the crystal is 2 hertz (purely theoretical for this example) then the LED being wired to this crystal will cycle twice per second, which means in a second you could turn it on for 1/2 a second and turn it off for 1/2 a second. That's where a microchip and crystal comes into play, the crystal or resonator creates a sort of on off cycle by resonating at a specific frequency measures in hertz (fractions of a time interval, seconds). Since all LED model TV's are digital devices and digital is controlled by on off states of 1's and 0's to get the intensity to 0.5 or 50% is not directly possible digitally. To control the intensity or different shades of the color purple the different diodes will be activated to different intensities so a light purple might have Red = 50% * Active, Green = Inactive, and Blue = 50% * Active which would give the same purple but dimmer. For purple Red = Active, Green = Inactive, and Blue = Active. LED TV's use tricolor LED's consisting of a red green and blue channel, the combination of these colors can be used to create other colors so a pixel or LED can have any color but the makeup will be a combination of the active states of LEDs that comprise that particular color. This means if you have a RED LED the light emitted will be in the red wavelength with very little infrared and very little orange light being emitted. What makes LEDs so efficient is they emit a very specific wavelength with a sharp rise and drop in the spectrum both before and after that specific wavelength. Of course, according to their charts there, our eyeballs should all but explode the instant we step outside.and I have only seen that happen once or twice over the years. :) But of course, who needs peer reviewed data in a round table discussion presented to push a particular new product? Blatant bad form by Essilor on this one. That obviously will change things even more. Further, there is zero mention of the final transmission plots of various light sources, as viewed by the human eye on the other side of an screen. No mention of the brand, intensity, or even the reported color temp of the various bulbs they claim to have mapped there. See the charts on page 5 in this presentation which show the spectrum emitted from common light sources: Actually incandescent and halogen lights produce proportionately less blue light compared to most other light sources.
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