6-bit vs. 8-bit LCDs

I was early in the testing phase of three new 22-inch LCDs when our podcast moderator Jeremy Williams commented that Dell’s E228WFP is a 6-bit color panel, as opposed to 8-bit. This took me by surprise as I’ve become so accustomed to seeing the 8-bit/ 16.7-million color spec associated with Dell’s monitors that I now take it for granted. FYI, 6-bit yields a total of 262,144 colors—clearly a noteworthy difference from 16.7 million colors. And yet I hadn’t noticed anything dramatically inferior about the E228WFP’s color reproduction.

But after digging into the published specs of all three 22-inch screens (the other two being HP’s w2207 and ViewSonic’s VG2230wm), I noticed that the color spec was suspiciously absent. I sent a query to all three vendors and then proceeded with my own research. Here’s what I discovered.

All desktop LCDs employ thin-film transistor (TFT) technology, but there are many variants of TFT. Of these variants, twisted nematic (TN) is the cheapest to produce. Also TN screens tend to have faster response times. Thus, many vendors use this technology for their mass-market displays. Mind you, this is distinct from their professional lines --- the displays we typically review and recommend. As I understand it, TN LCDs are for the most part incapable of 8-bit color. To bridge that huge gap between 8-bit's 16.7 million colors and the 262,144 colors 6-bit is capable of, vendors use compensation techniques: either dithering, which combines adjacent pixels to simulate a desired shade, or more commonly, “frame rate control” (FRC), which rapidly cycles the 6-bit pixels to simulate the shades you’d get natively from an 8-bit panel.

Eventually, I got confirmation from all three vendors that the 22-inch displays indeed feature 6-bit/FRC technology. And my opinion from this limited sampling is that 6-bit color creates a noticeably less impressive picture than 8-bit color, but doesn't result in any image artifacts. It's worth considering if you want more screen for your scratch.

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lcd, monitor, display, flat panel

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