what are monochrome 4K-LCDs used for? - Page 1
Forum section: electronics / general

author: 0db
author_rank: Frequent Contributor
timestamp: March 20, 2020, 09:37:52 am
content: I can understand color and retina 4K LCDs, but what about monochrome 4K-LCDs?I see a lot of these LCDs for sale, but I fail to understand the purpose ...

author: AndyC_772
author_rank: Super Contributor
timestamp: March 20, 2020, 09:48:46 am
content: MSLA printers?https://www.fepshop.com/shop/3d-printers/phrozen/phrozen-sonic/

author: Deni
author_rank: Regular Contributor
timestamp: March 20, 2020, 09:51:16 am
content: Quote from: 0db on March 20, 2020, 09:37:52 amPerhaps in medical imaging (X-rays). Subtle shades in this kind of imaging are hard to reproduce with RGB-types.

author: 0db
author_rank: Frequent Contributor
timestamp: March 20, 2020, 09:54:57 am
content: Quote from: AndyC_772 on March 20, 2020, 09:48:46 amQuote from: Deni on March 20, 2020, 09:51:16 amVery interesting! Never heard before, thank you guys!

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: March 20, 2020, 10:01:08 am
content: Also any application where high contrast and/or good power efficiency is more important than colour - colour LCDs lose about 2/3rds of the backlight power in the RGB filters.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 20, 2020, 12:53:26 pm
content: If the response time is fast enough, they can display colors with a RGB backlight pulsing individual colors just like a DLP projector. In practice, it's difficult to make LCDs fast enough for that to work well, but 8 years or so ago, there was a tablet that used that technology to make a dual mode display capable of operating as a color display with about half the power usage of conventional LCD (since the fast refreshing uses a little more power) or as a monochrome eink like display with the backlight turned off.

author: tooki
author_rank: Super Contributor
timestamp: March 20, 2020, 01:26:41 pm
content: Quote from: NiHaoMike on March 20, 2020, 12:53:26 pmUgh, I hope this doesn’t become popular until the technology allows for extremely fast rates like 1000Hz. I am sensitive to flicker, and I can spot a DLP projector from a mile away when it’s a mostly dark background with a few bright objects, as the famous rainbow effect.I know this technique is already used in small LED-lit LCD projectors.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 20, 2020, 04:04:04 pm
content: By monochrome, do you mean grayscale (and if so, how many bits per pixel?) or just 1 bit per pixel?

author: mzzj
author_rank: Super Contributor
timestamp: March 20, 2020, 06:45:30 pm
content: Quote from: NiHaoMike on March 20, 2020, 12:53:26 pm3LCD is common way to do projectorshttps://electronics.howstuffworks.com/lcd-projectors1.htm

author: tooki
author_rank: Super Contributor
timestamp: March 20, 2020, 11:42:12 pm
content: Quote from: mzzj on March 20, 2020, 06:45:30 pmWell yeah, we all knew that. But the discussion is about using one LCD with an alternating-color light source.

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 21, 2020, 12:31:55 am
content: Quote from: tooki on March 20, 2020, 01:26:41 pmThat's exactly why it has not caught on. I'm not sure why so far, nobody has tried that in a device that's primarily monochrome with colors mostly just for minor things like accents, for example, an ebook reader. (The tablet tried to be a normal tablet with "eink mode".)

author: james_s
author_rank: Super Contributor
timestamp: March 21, 2020, 12:42:13 am
content: I haven't looked at the state of the art, but B&W CRTs were very common for medical imaging like ultrasound, they provide a sharper more detailed display than color CRTs and the same is likely true for LCDs. Back in the day at least TV studios also used B&W monitors alongside color because they tend to show more detail and make some types of flaws in the image more visible.

author: amyk
author_rank: Super Contributor
timestamp: March 21, 2020, 01:39:28 am
content: Eizo makes a bunch of them for medical applications. Prices are in the 4-5 figure range.

author: Circlotron
author_rank: Super Contributor
timestamp: March 21, 2020, 02:17:53 am
content: You could say a 4K lcd actually has 12K horizontal pixels whereas a monochrome one would only have 4K. Wouldn’t the colour one give better resolution if it used sub pixel rendering?

author: james_s
author_rank: Super Contributor
timestamp: March 21, 2020, 04:57:47 am
content: Perhaps? But maybe the color filters would result in a less clear image? There must be a reason these things exist.

author: helius
author_rank: Super Contributor
timestamp: March 21, 2020, 05:35:56 am
content: Subpixel rendering is only useful for bitonal objects like fonts (and most implementations only support fonts).

author: tooki
author_rank: Super Contributor
timestamp: March 21, 2020, 01:21:06 pm
content: Quote from: NiHaoMike on March 21, 2020, 12:31:55 amHow would that make any difference? It's not motionin the imagethat causes the rainbow effect, it's eye movements of the viewer.I mean, you could use very fast backlight pulsing to change the backlight color of an e-reader, but what use is that, or rather, what about that wouldn't be achievable with regular LED backlighting, just with RGB LEDs or various shades of white, if it's just adjusting the color temperature.Quote from: Circlotron on March 21, 2020, 02:17:53 amIn theory, yes. But it comes with its own tradeoffs, like the fact that white areas have three times as many gaps in them as a monochrome LCD would.Quote from: helius on March 21, 2020, 05:35:56 amThere's no reason for it to apply only to bitonal things — if anything, it only really works well for things that have variations in brightness, which is why we invariably apply subpixel rendering to antialiased font rendering, not bitonal rendering. Without the antialiasing, the color fringing is too distracting.Most implementations of subpixel rendering are very limited in where they can apply, insofar as I don't know of any that are applied to anything but text, and many of those only apply it to text on white or black backgrounds. But it works beautifully on color backgrounds, too, and there's no reason it couldn't be applied to complex backgrounds*. I suspect that if high-resolution (as in, pixel density) displays hadn't become available, we might have invested the effort to make our graphics drawing engines perform subpixel rendering on everything. But with the high-res displays with pixels so small as to be invisible becoming commonplace (and many of them using complex nonuniform subpixel arrangements), it became easier to simply brute force it in hardware.*and this can be tested by taking subpixel-rendered text on a white background, and then photoshopping that onto an arbitrary background image. The result is actually flawless. (At least, in my experiments of essentially using it as subpixel "ink" onto a light background. I haven't tried anything where the text is lighter than the background.)

author: jogri
author_rank: Frequent Contributor
timestamp: March 21, 2020, 01:42:39 pm
content: Quote from: amyk on March 21, 2020, 01:39:28 amThose are used for viewing X-ray images, they even need to be calibrated every so often to make sure the colour tones are exactly right as the difference between healthy tissue and a tumor can be hard to see (remember, we are talking about differences in density), especially with small tumors.If you see them on sale on ebay etc they probably failed the test/calibration.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 21, 2020, 03:11:03 pm
content: Quote from: Circlotron on March 21, 2020, 02:17:53 amNah. The spatially distributed RGB dots will always make the image look a little fuzzier. If you want to look at grayscale images only, you can't beat a purely grayscale panel IMO.Besides, given they are simpler to design, they may also have better luminance resolution (that's why I was asking for bit depth). A typical RGB panel has 6 to 8 bits per individual dot, the grayscale panels may have more (although I'd like to see specs!)

author: Miyuki
author_rank: Frequent Contributor
timestamp: March 21, 2020, 04:12:18 pm
content: EIZO medical monochrome panels have up to 14-bit tones it is way more than conventional ones