Pixel Qi netbook display replacement kit on sale

[HarryT]

Originally Posted by Shaggy

That's only with the backlight turned off though, which current LCD screens can't do. With the backlight on it's a full color display like current LCD.

Isn't it rather poor resolution, though, compared to current LCD screens? That's what I don't really "get" about it; no matter which way you look at it, it appears to be a compromise. I'm not really sure what its intended market is.

[LDBoblo]

Originally Posted by HarryT

Isn't it rather poor resolution, though, compared to current LCD screens? That's what I don't really "get" about it; no matter which way you look at it, it appears to be a compromise. I'm not really sure what its intended market is.

1024x600 is the lower of the two standard netbook resolutions, (the other being 1366x768, which until recently was only for the higher-end netbooks).

However, it is not a "poor" resolution, and its effective monochrome resolution (3072x600) is quite a bit higher than that of E-Ink.

[RoboRay]

Originally Posted by Papi

Interresting...I don't know if the "new" PixelQi is very different from the one you have, but the one thing that struck me when I saw the pic posted by olis is that the E-Ink screen looks way more white, the PixelQI being kind of green~gray, which you confirmed. That's a noticeable drawback to me, Pixel QI can make black as dark they want and have the highest contrast technically, I prefer white as background color

The Pixel Qi screens (or, at least the older one on my OLPC), while grayish in color with the backlight off do produce white with the backlight turned on.

I've noticed that I do tend to pick a somewhat larger font than my wife does on her Kindle, which may be helping me compensate for the lower contrast by using larger type.

The contrast is good enough for me, especially considering that you've got a color display with the backlight turned on. I use the device for general websurfing and reviewing photographs, too, so I'm willing to sacrifice a bit of contrast in low-power reflective mode.

As has already been noted, the Pixel Qi screen really isn't designed to be a perfect e-reader screen... It's an all-purpose screen that functions as, among other things, a good e-reader screen. Jack of all trades, master of none. If you're going to keep a laptop or tablet PC around along with your e-reader, Pixel Qi may not be the best choice for your reader. I love it because it lets me combine those two devices into one.

[LDBoblo]

Originally Posted by RoboRay

The Pixel Qi screens (or, at least the older one on my OLPC), while grayish in color with the backlight off do produce white with the backlight turned on.

I've noticed that I do tend to pick a somewhat larger font than my wife does on her Kindle, which may be helping me compensate for the lower contrast by using larger type.

The contrast is good enough for me, especially considering that you've got a color display with the backlight turned on. I use the device for general websurfing and reviewing photographs, too, so I'm willing to sacrifice a bit of contrast in low-power reflective mode.

As has already been noted, the Pixel Qi screen really isn't designed to be a perfect e-reader screen... It's an all-purpose screen that functions as, among other things, a good e-reader screen. Jack of all trades, master of none. If you're going to keep a laptop or tablet PC around along with your e-reader, Pixel Qi may not be the best choice for your reader. I love it because it lets me combine those two devices into one.

Also, the current Pixel Qi screen is quite superior to the OLPC XO screen.
http://www.olpcnews.com/hardware/scr...-15_hands.html

[RoboRay]

The new one does appear to have better contrast than the OLPC screen. I'm hoping they come out with a higher-resolution display next, though, which at least matches the DPI achievable on the old one.

[Papi]

Originally Posted by RoboRay

The Pixel Qi screens (or, at least the older one on my OLPC), while grayish in color with the backlight off do produce white with the backlight turned on.

I've noticed that I do tend to pick a somewhat larger font than my wife does on her Kindle, which may be helping me compensate for the lower contrast by using larger type.

The contrast is good enough for me, especially considering that you've got a color display with the backlight turned on. I use the device for general websurfing and reviewing photographs, too, so I'm willing to sacrifice a bit of contrast in low-power reflective mode.

As has already been noted, the Pixel Qi screen really isn't designed to be a perfect e-reader screen... It's an all-purpose screen that functions as, among other things, a good e-reader screen. Jack of all trades, master of none. If you're going to keep a laptop or tablet PC around along with your e-reader, Pixel Qi may not be the best choice for your reader. I love it because it lets me combine those two devices into one.

That's what I was looking for : an "all-in-one" device, if the reading part is not too bad...I mean if reading an hour or so on it doesn't hurt the eye. The best would be to be able to compare them both, I'll try that if the PixelQI screen hits the mass market. I don't know how much a standard tablet PC costs, but if it gets pretty low, I fear E-Readers will suffer from it and maybe disappear, even if they're better at what they do. Or they would have to be considerably cheaper.

One thing I didn't quite understand : when the backlight is turned off, you get automaticely in black & white / higher resolution mode ?

[RoboRay]

Originally Posted by Papi

One thing I didn't quite understand : when the backlight is turned off, you get automaticely in black & white / higher resolution mode ?

On the OLPC, the backlight can be turned on and off independently of setting the screen to the high resolution B&W "e-reader" mode. So, you really end up with four possible combinations...

Backlight ON and reader-mode OFF = full color normal-resolution display (my normal mode for anything but reading.)

Backlight ON and reader-mode ON = monochrome high-resolution display (my normal mode for reading indoors in low to moderate lighting conditions, adjusting the backlight level to the minimum I need for comfortable reading.)

Backlight OFF and reader-mode ON = monochrome high-resolution display (my normal mode for reading outdoors in sunlight or indoors under a lamp.)

Backlight OFF and reader-mode OFF = monochrome normal-resolution display (haven't found a good reason to use it this way, as you can't see colors without the backlight and you could be separating the colored pixels for the high-rez reader mode instead.)

Pixel Qi screens are similar to standard LCDs in that each pixel produces a single color (red, green or blue) which are combined three at a time to produce the desired colors at each point on the display. Pixel Qi screens are unlike standard LCDs in that the "groups" of three pixels that normally work together to produce color combinations can also work independently of each other to produce monochrome pixels at thee-times the color resolution.

Here's what the OLPC Pixel Qi screen looks like under a microscope:



Note that the screen is essentially producing colors through dithering, as each pixel is physically limited to a single color. You've got to put your eye right up next to the display to really see the dithering effect, but it's happening. This is not a perfect color LCD just like it's not a perfect e-reader display. It just happens to be the only display that does a good job at both.

I'm presuming that the new Pixel Qi screens work about the same way, but I haven't had my hands on one yet to verify it.

I have countless hours reading on my OLPC in all conditions and haven't had any headaches or eye problems yet. I spent six months reading almost exclusively on this screen while traveling, up to 8 hours or so at a stretch, and am quite happy to keep reading on Pixel Qi screens.

[LDBoblo]

Originally Posted by RoboRay

Here's what the OLPC Pixel Qi screen looks like under a microscope:

From what I've been reading, it seems that standard Pixel Qi has a more conventional RGB subpixel array based on square(ish) pixels. This allows it to take advantage of subpixel rendering to boost text resolution. In black and white mode, they boast a threefold horizontal resolution increase, which meshes with a standard horizontal RGB array.

The effective monochrome resolution of Pixel Qi in its current state is 3072x600.
The effective monochrome resolution of the OLPC XO series is 1200x900.

The effective RGB resolution of Pixel Qi (full transmissive) is 1024x600.
The effective RGB resolution of OLPC XO series is estimated at 984×738. (link)

Hope that's helpful.

[Papi]

Very interresting, thanks to both of you. Only thing that is still unclear to me is : how does a Pixel QI screen "physically" displays black & white ? because on the picture it seems each pixel is red / green / blue, I guess the "white" part of the B&W mode is just the background of the screen, but what about the "black" ? Though I don't know how they render it in regular LCD also, i guess the pixels have to "block" the backgound light.
Sorry for all the questions, i feel a bit like poluting the thread...

[LDBoblo]

Originally Posted by Papi

Very interresting, thanks to both of you. Only thing that is still unclear to me is : how does a Pixel QI screen "physically" displays black & white ? because on the picture it seems each pixel is red / green / blue, I guess the "white" part of the B&W mode is just the background of the screen, but what about the "black" ? Though I don't know how they render it in regular LCD also, i guess the pixels have to "block" the backgound light.
Sorry for all the questions, i feel a bit like poluting the thread...

In the case of OLPC at least (I can't remember if current Pixel Qi is the same), the reflective layer is between the LCD and the color filters. The color filters are between the reflective layer and the backlight.

So basically, the backlight goes through the color filters, through the semi-permeable reflective layer, through the LCD (which is monochrome of course). Outside light bounces off the reflective layer and never reaches the color filters. Color filters reduce light transmission significantly, so it makes sense to put the reflective surface in front of them.

There are lots of other things going on in a display, and lots of other layers, but hopefully that helps address your question of monochrome versus color. To restate, the reflected light doesn't reach the color filters, which are behind the reflective layer.

It's late though, and if I'm mistaken, someone please correct me.

[RoboRay]

Originally Posted by Papi

Very interresting, thanks to both of you. Only thing that is still unclear to me is : how does a Pixel QI screen "physically" displays black & white ? because on the picture it seems each pixel is red / green / blue

The image I posted is the OLPC display showing a "white" background. In normal viewing (not blown up under the microscope) your eye interprets the closely spaced red, green and blue pixels to be a white field. If you put your eye right up next to the display you can begin to see the different colors of the individual pixels, but at normal handheld or desktop viewing distance it appears to be a solid white field.

[RoboRay]

Originally Posted by LDBoblo

In the case of OLPC at least (I can't remember if current Pixel Qi is the same), the reflective layer is between the LCD and the color filters. The color filters are between the reflective layer and the backlight.

So basically, the backlight goes through the color filters, through the semi-permeable reflective layer, through the LCD (which is monochrome of course). Outside light bounces off the reflective layer and never reaches the color filters. Color filters reduce light transmission significantly, so it makes sense to put the reflective surface in front of them.

There are lots of other things going on in a display, and lots of other layers, but hopefully that helps address your question of monochrome versus color. To restate, the reflected light doesn't reach the color filters, which are behind the reflective layer.

It's late though, and if I'm mistaken, someone please correct me.

I believe that's an accurate description of how the original OLPC Pixel Qi panels work. I don't know how or if the new models are different.

More information on the OLPC display here: http://wiki.laptop.org/go/Display#Un...display_system

[MikeFromHC]

Originally Posted by LDBoblo

In the case of OLPC at least (I can't remember if current Pixel Qi is the same), the reflective layer is between the LCD and the color filters. The color filters are between the reflective layer and the backlight.

So basically, the backlight goes through the color filters, through the semi-permeable reflective layer, through the LCD (which is monochrome of course). Outside light bounces off the reflective layer and never reaches the color filters. Color filters reduce light transmission significantly, so it makes sense to put the reflective surface in front of them.

There are lots of other things going on in a display, and lots of other layers, but hopefully that helps address your question of monochrome versus color. To restate, the reflected light doesn't reach the color filters, which are behind the reflective layer.

It's late though, and if I'm mistaken, someone please correct me.

That's pretty much the way that Mary Lou Jepson explained it - and she invented it.

She was a bit more simplistic and said they put a mirror behind the LCD, then put little holes in the mirror so the back-light could shine through.

[gastan]

Originally Posted by Shaggy

I have no idea what the contrast levels really are, but I do know that Pixel Qi have said themselves that it's lower than eInk.

I don't know where you read that but it is either flat out wrong or hopelessly outdated. Pixel Qi states that their screens have, "...better contrast ratio and equivalent reflectance typical of the best electrophoretic displays." (emphasis added) (source: http://www.pixelqi.com/)

[LDBoblo]

Originally Posted by gastan

I don't know where you read that but it is either flat out wrong or hopelessly outdated. Pixel Qi states that their screens have, "...better contrast ratio and equivalent reflectance typical of the best electrophoretic displays." (emphasis added) (source: http://www.pixelqi.com/)

People seem to be confusing white reflectance with contrast. Pixel Qi does not quite achieve the same white state an electrophoretic display can (despite the marketing on their front page), but the black of a reflective LCD can be quite a bit superior to the black of an EPD. Thus in some of the pictures, the background may not appear as "white" (light gray) as an EPD, but the text should be equally or more readable.

Seems the newest E-Ink might catch up a bit in terms of contrast, but still lacks speed and the backlit color option.