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Two LCDs, front to back, provide much better contrast by blocking more of the light in the liquid crystal layers. The rear one is greyscale. https://www.reddi

• rbanffy 2y ago
  OTOH, an LCD, at best, let's 50% of the light pass through it, so, for two stacked LCD panels, you'll need a much brighter backlight.
  • toast0 2y ago
    LCDs work on polarization... you typically have an unpolarized source, run it through a polarized filter which is where your 50% loss comes from, then the LCD changes or doesn't the polarization, and you run it through a filter again. If you stacked a second LCD, you shouldn't see a second 50% loss, the light is already polarized by the first LCD.
    • rbanffy 2y ago
      You are right - the 50% loss comes from the filters, but I forgot to count the loss from the filters. You could add a second monochrome LCD on top of the first one for the same result. I must be wrong, because this sounds very trivial.
• fngjdflmdflg 2y ago
  >The rear one is grayscale. If I understand correctly, you're saying that there is a rear LCD that only either lets light in or blocks it without caring about the color? That's interesting. As for why they aren't investing in this then, it's might be at least in part due to the power usage which would make it unsuitable for battery powered devices such as the iPad mentioned in the article.