What is the extra cost of RGB backlights?

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Nightbird

[H]ard|Gawd
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LED backlighting in color screens comes in two flavors: white LED backlights and RGB LED backlights[1]. White LEDs are used most often in notebooks and desktop screens, and in virtually all mobile LCD screens. A white LED is actually a blue LED with yellow phosphor to give the impression of white light. The spectral curve has big gaps in the green and red parts. RGB LEDs consist of a red, a blue, and a green LED and can be controlled to produce different temperatures of white. RGB LEDs for backlighting are found in high end color proofing displays such as HP DreamColor LP2480zx monitor or selected HP 8730w notebooks, as well as newer consumer grade displays such as Dell's Studio series laptops which have an optional RGB LED display.

RGB LEDs can deliver an enormous color gamut to screens. When using three separate LEDs (additive color) the backlight can produce a color spectrum that closely matches the color filters in the LCD pixels themselves. In this way, the filter passband can be narrowed so that each color component lets only a very narrow band of spectrum through the LCD. This improves the efficiency of the display since little light is blocked when white is displayed. Also, the actual red, green, and blue points can be moved farther out so that the display is capable of reproducing more vivid colors. CCFL backlighting has also improved in this respect. Many current LCD models, from cheap TN-displays to color proofing S-IPS or S-PVA panels, have wide gamut CCFLs representing more than 95% of the NTSC color specification.
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After reading reviews covering low color gamut in new TN panels, I was torn about how you had to choose between accurate color representation or fast response rate and 120hz. Then I stumbled onto this little blurb on Wikipedia about RGB LEDs. A quick search revealed on LaCie LCDs ranging from 1400$ for a 20' to 3200$ for a 30" (S-PVA 125% NTSC gamut).

My simple questions are:
1. Can this backlight be used to improve gamut for 24" 120hz TNs?
2. Can it be done for less than 1000$ for a 24"?
3. Will anyone (Asus, LG, etc) bother making it?

http://h20331.www2.hp.com/hpsub/cache/596803-0-0-225-121.html
LG 24" IPS RGB LED backlight professional 1800$
 
You can get a used LP2480ZX on ebay for like ~$1000. I saw one yesterday sold for upward of $900.
 
anodize said:
You can get a used LP2480ZX on ebay for like ~$1000. I saw one yesterday sold for upward of $900.
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That's an IPS professional display for graphics artists, I'm wondering more if the technology is suitable for TN monitors at all. We won't get as good a gamut as IPS of course, but if it can be used it would be a very nice 120hz TN monitor.
 
Nightbird said:
After reading reviews covering low color gamut in new TN panels, I was torn about how you had to choose between accurate color representation or fast response rate and 120hz.
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The gamut has nothing with to do with color accuracy and since you most likely will be viewing sRGB content the accuracy in practice will be much worse on a wide gamut monitor.

That TN panels have low color gamut is the best feature they have going for them.

The backlight is a huge part of the cost of a monitor. I really doubt RGB LEDs will ever come to TN displays.
 
The problem is there just isn't a lot of point right now. It costs more and doesn't gain you anything except a little wider gamut. That's why everything is white LED and CCFL.

White LED is useful because it uses less power and you can make a thinner display. So for laptops, it is great. You see it in other displays as well, but it isn't as important in desktop displays since power consumption isn't such a big deal. It is also used in big screen TVs mostly because it keeps the thickness down, but less power is also nice since they use more overall.

CCFLs are still the way to go for everything else. You can make the rather wide gamut if you like, and they are really cheap to do. They tend to be pretty even in terms of backlighting when done right as well. So for most desktop displays, they are the choice. For cheaper displays they keep the cost down as much as possible and for more expensive ones they allow for good backlighting with a wide gamut if desired.

RGB LEDs just cost too much, and use too much power. They use more power than CCFLs (at least they did last I checked) and are the most expensive solution. For all that they offer very little, just a slightly wider gamut than CCFLs (not much wider mind you) and quicker warmup time.

I don't expect you'll see many displays with it unless they figure out how to bring costs down, or it starts offering an image quality better than CCFLs by a good margin.
 
Nightbird said:
That's an IPS professional display for graphics artists, I'm wondering more if the technology is suitable for TN monitors at all. We won't get as good a gamut as IPS of course, but if it can be used it would be a very nice 120hz TN monitor.
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It is suitable for TN. My 17'' laptop screen is RGB backlit TN panel. It looks pretty good.
 
anodize said:
It is suitable for TN. My 17'' laptop screen is RGB backlit TN panel. It looks pretty good.
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Agreed. I have a M17xR2 with the RGBLED screen and it is a huge improvement, especially when compared to most existing laptop screens. Unfortunately it still has the typical poor TN contrast and weird shifting effects when you change viewing angles.

It will be a while before we see mainstream RGBLED backlit monitors for desktop PCs, if ever. It really looks like OLED is the future for desktop monitors.
 
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