is it really that hard to buy that 24-bit is the current limit of the technology due to physical limitations or cost?
Not at all. In fact, my question is not challenging what the current bit depth is on LCD panels. To be clear, I realize that most LCD panels are capable of 8 bit color depth. Just to note...I was under the impression that the NEC 2180WG-LED had an LCD panel capable of 10 bit color depth, but after reading the specs again, I see that it is in fact an 8 bit panel that uses a Frame Rate Conversion technique to simulate 10 bit color, much like how 6 bit panels simulate 8 bit color. In fact, the 2180WG-LED is capable of displaying greater than 1 billion colors.
But what makes an 8 bit panel an 8 bit panel? It is the controller chip that drives the pixels. The controller is responsible for deciding what voltage gets sent to the crystals of a pixel. So my original question is still hanging out there, which was "Why would it not be possible to adjust the voltage that constitutes a fully-on (white) pixel, as well as all of the voltages between white and black?" or in other words, the contrast.
2 answers have been given so far:
1)LCDs are 8-bit/channel devices. This means that there are only 256 possible voltage levels available to each crystal. To adjust contrast you'd reduce the number of voltage levels sent to each crystal in order to maintain your custom contrast setting.
2)It's a fixed limitation of technology as it currently stands. Until they can make LCD crystals more sensitive to varying voltage, 8-bit is the limit.
If crystal sensitivity was indeed the issue, then everything would make sense. However I don't believe that to be true. Imagine if you could put your finger on a liquid crystal and twist it around. It would twist in a fluid motion, it wouldn't click into place every X degrees like a ratchet. As for number 1, I already explained above why the voltage output range of the controller could still be varied even though the controller only has 256 output levels.
I'm not trying to be difficult here, I'm just looking for a technical explanation that is logical. Remember, the whole point of my question has to do with contrast adjustment. It was stated on here, and I've seen the same thing posted elsewhere, that contrast can not be adjusted on LCDs. However, I've also read the exact opposite on several occasions. In addition several LCDs have contrast controls. Since each manufacturer is free to implement the controls however they want, I realize that some have chosen to simply alter the video signal coming from the computer in order to affect contrast, which is not a good thing. Varing the voltages driving the liquid crystals seems, to me, to be an alternative way of affecting contrast. Since I'm speculating, I'm looking for an answer from someone that knows for sure, without speculation, that that indeed is, or is not, a method that can be used.