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Author Topic: LCD Monitor Recommendations  (Read 441032 times)
MarkGoddard
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« Reply #40 on: February 02, 2006, 04:56:59 PM »
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Does anyone know if the Dell 2001FP suffers from the same brightness issues as the other DELLs.  I have this monitor at work (Software Development) and have been thinking of getting one for home for use with Photoshop CS2 (calibrated with the Spyder2).
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plattners@gacnw.com
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« Reply #41 on: February 08, 2006, 11:19:49 PM »
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I am fairly challenged when it comes to calibration issues, but I do have an issue that seems to relate to this thread. I have an HP2335 lcd monitor. My problem is, after calibrating it carefully 2x, I can't begin to replicate the bright, brilliant color I see on the screen when I print on my Epson 2200. What would be the best way to correct the situation? I have experimented with the monitor, turning down the brightness by about 50% and reducing the contrast somewhat as well. Should I put my HP monitor on Ebay and hook my old and excellent CRT--Mitsubishi 2060u--back up?
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cmcfarling
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« Reply #42 on: February 13, 2006, 10:24:26 AM »
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As mentioned in the quote from Karl Lang, any such adjustments are a bad idea. The color characteristics of LCD displays are set at the factory. There is no changing them. Period. The only analog adjustment and thusly, the only thing you can be calibrated (profiling is a separate process) is the brightness of the backlight.

Any LCD with adjustment controls that go beyond just brightness are going to adjust the LUTs and thusly degrade the display's ability to render all of the colors it is capable of displaying thus making accurate color adjustments and proofing more difficult.

If I had to guess as to why companies include all those contrast and color adjustment controls it would be to make the displays more familiar to users used to older CRT technology. Not to mention, it gives the marketing department something to add to the features list ("Color controls for accurate color!!").

I have read similar statements from others in "color circles" while researching LCDs. I must say that I'm not convinced that is the case (and of course may be wrong). Why would it not be possible to adjust contrast on an LCD? After all, just like a CRT, voltage is what determines the luminance of a pixel. In a CRT, increasing the voltage causes the phosphor to glow brighter. In an LCD, increasing the voltage (assuming that the native state of the pixel is OFF) causes the liquid crystals to twist therefore allowing more light to shine through. 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?

After all, the phone sitting on my desk has an LCD display and no backlight. I can adjust the contrast of the display to make the numbers lighter or darker. Of course there is a huge difference between a 20" color LCD and a two line LCD on a phone, but the machanics behind the two are the same-voltage affecting the twisting motion of liquid crystals.

Chris McFarling
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61Dynamic
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« Reply #43 on: February 13, 2006, 11:00:54 AM »
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I have read similar statements from others in "color circles" while researching LCDs. I must say that I'm not convinced that is the case (and of course may be wrong). Why would it not be possible to adjust contrast on an LCD? After all, just like a CRT, voltage is what determines the luminance of a pixel. In a CRT, increasing the voltage causes the phosphor to glow brighter. In an LCD, increasing the voltage (assuming that the native state of the pixel is OFF) causes the liquid crystals to twist therefore allowing more light to shine through. 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?

After all, the phone sitting on my desk has an LCD display and no backlight. I can adjust the contrast of the display to make the numbers lighter or darker. Of course there is a huge difference between a 20" color LCD and a two line LCD on a phone, but the machanics behind the two are the same-voltage affecting the twisting motion of liquid crystals.

Chris McFarling
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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. A LCD monitor needs every bit available to it in order to render an image accurately. There is no room to throw information away.

Your phone is different. Since it has no backlight it must be monochrome which means it does not have to be able to render millions of different color values. It is simply black and "white" possibly with a shade or two in between. If you can adjust contrast, I'd guess it is a 4-bit display offering 16 different levels for the crystals to twist.
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cmcfarling
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« Reply #44 on: February 13, 2006, 12:29:32 PM »
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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.

But are those 256 levels fixed? Not being familiar with the intricicies on LCD microelectronics, I'll just use arbitrary voltage numbers to illustrate my point.

The signal sent to the display allows for 256 possible values for each pixel, in the case of an 8 bit data path. The LCD contoller chip, in turn, can output 256 separate voltages. Let's say a level 0 signal equals 0mV of realized voltage to the crystals of a pixel while level 255 equals 100mV. What's to keep the electronics from deciding that signal level 255 equals 90mV instead? The display is still allowed to produce 256 distinct output voltages, they'd just be compressed into a smaller range.
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61Dynamic
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« Reply #45 on: February 13, 2006, 02:05:09 PM »
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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.
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cmcfarling
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« Reply #46 on: February 13, 2006, 02:26:07 PM »
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I'm not sure I buy that. From what you're saying, the limitation is in the liquid crystals themselves, that they can't be coaxed into twisting into increments other than those in a fixed 256 step range.

From what I understand, the twisting motion (of the crystals themselves)  is an analog function meaning that there is really an infinite amount of steps between on & off. The limitation then comes from the digital chip in the display that is designed to only send 256 distinct voltages.

I would think that an analogy could be drawn to a CRT electron beam. The bean itself, being analog, has an infinite range of intensity (between off and full power). The computer chips upstream are what limit it to a definite range of 256 values.

In addition, NEC & Eizo already have displays that are capable of 10 bits/pixel. The key there is a different controller chip, I don't believe they're using liquid crystals that are any different than previous technology.
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61Dynamic
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« Reply #47 on: February 13, 2006, 03:02:58 PM »
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I'm not sure I buy that. From what you're saying, the limitation is in the liquid crystals themselves, that they can't be coaxed into twisting into increments other than those in a fixed 256 step range.
[{POST_SNAPBACK}][/a]

You gotta stop comparing LCDs to CRTs. They accomplish the same goal but are extremely different technologies.

Considering how recently 24-bit displays have become common in the mass market vs the previous 18-bit displays is it really that hard to buy that 24-bit is the current limit of the technology due to physical limitations or cost?

If it was possible to go beyond 24-bit wouldn't we see some displays of that nature, even if only in the high-end of the market? The fact is there are no displays that exceed 24-bits.

On that note:
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In addition, NEC & Eizo already have displays that are capable of 10 bits/pixel. The key there is a different controller chip, I don't believe they're using liquid crystals that are any different than previous technology.
Exactly. The LCD technology is no different in terms of bit-depth. If you look at the specs for those displays they list their color depth for the LCD at 16.7million, which is 24-bit.

The 14-bit/channel (current models) part comes from an [a href=\"http://www.eizo.com/products/graphics/cg210/features.asp#14bit]image processor[/url] that intercepts the signal from the computer, allows you to make adjustments on the display and then takes that data and scales it down to a 24-bit output.
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cmcfarling
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« Reply #48 on: February 13, 2006, 04:25:29 PM »
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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.
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TimothFarrar
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« Reply #49 on: February 13, 2006, 07:07:13 PM »
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cmcfarling, I think you are definatly on to something here. There would be an easy way to test your theory. Create an image the size of the screen that is a 8x8 grid of flat colors (say green shades 0 to 63 in sequence). If the display is capable of displaying all the shades, with large enough blocks of color your eye will see the difference between adjacent shades. Now if by adjusting the brightness and contrast on the display, the difference between the shades completely disappears, then the display is running out of unique displayable shades. Of course you will want to do this outside photoshop, so as there is a non-color managed output.

I just did a similar test in Image Ready (which does not have a color managed output) on a 17" G4 powerbook which also has a Samsung 910T (a 8bit, not dithered 6bit display) attached to it. Both displays are calibrated to a 5000K white point.

Even without adjusting the brightness and contrast from their current calibrated settings, I cannot see the difference between all the first 0-31 shades (even in the brighter shades). Also moving the window between the two monitors adjusts which color shades blend into the same output shade. So on the first display 17 and 18 are the same output shade on the monitor, then on the other monitor you can tell the difference between those shades.

Both of the displays are unable to show all 32 individual shades. Based on this test, my guess is that 61Dynamic is right for the 2 displays I did the test on. BTW, I am using a VGA input to my second display.

I would also guess that the difference between the a high end LCD with a 10 or 14bit LUT that uses the same 8bit LCD panel as a inexpensive LCD that doesn't have a LUT, is that the high end LCD uses some time based dithering to simulate the 1024 or 4096 shades possible via the LUT.
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jani
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« Reply #50 on: February 14, 2006, 07:51:14 AM »
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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.
You're missing the really obvious bit:

Precision.

While it may be possible for the crystals to twist in more than 256 different angles, it's important that it's the same angles every time for every crystal.

Apparently, the display manufacturers still think this is so difficult that they're instead opting for the solution of providing per-pixel 256-level backlighting instead.
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Jan
cmcfarling
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« Reply #51 on: February 14, 2006, 11:00:57 AM »
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cmcfarling, I think you are definatly on to something here. There would be an easy way to test your theory. Create an image the size of the screen that is a 8x8 grid of flat colors (say green shades 0 to 63 in sequence).


Good idea. I went ahead and did that. An 8 x 8 grid with patches in incements of 4 levels (0,4,8,12......) Since I'm not near any good displays at the moment, I'm using an iBook 14" and a 2 year old Hyundai 17" LCD. The iBook doesn't have a contrast setting so I can't really do much there. I will note that I can distinguish between levels 0 and 4 though. 255 and 252 are indistiguishable while there is a difference between 252 and 248. So overall the iBook LCD is not clipping too many levels.

On the Hyundai (contrast set to 100), the first 3 pathes, levels 0-12 all appear the same. I can distinquish between 12 and 16 though. The other end is just tlike the iBook, 255 and 252 are indistiguishable while there is a difference between 252 and 248. When I lower the contrast to 0, levels 0-16 now blend together. The highlight end of the scale doesn't change much.

So, just as expected, adjusting the contrast does decrease the the number of usable levels being sent to the display. I'm not disputing that at all. In this case I'm using a fairly low end display so I would not expect any special color controls. But does it *have* to be that way? I don't see why a better display couldn't employ some more sophisticated electronics that allow for better contrast adjustment, and I wonder if any such dislays exist already.

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While it may be possible for the crystals to twist in more than 256 different angles, it's important that it's the same angles every time for every crystal.

Can you explain why you think that to be true?
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jani
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« Reply #52 on: February 14, 2006, 03:50:49 PM »
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While it may be possible for the crystals to twist in more than 256 different angles, it's important that it's the same angles every time for every crystal.
Can you explain why you think that to be true?
Isn't that self-evident?

Okay, let's try a thought experiment.

Assume that we have two displays, equally precise. One can be adjusted to 256 different intensities/angles, another supports 1024.

Let's assume that the error in angles is 1/512.

For the display supporting 256 different intensities, that error is insignificant. A value of e.g. 200 will always be represented as reasonably close to 200.

For the display supporting 1024 different intensities, it means that you cannot be certain whether an input value of e.g. 900 will turn out as 898, 899, 900, 901 or 902.

Now you can apply similar margins of error to other adjustments regarding the levels of individual crystals, and see that if you want the higher precision in levels, you also need the higher precision for the individual crystals.
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Jan
cmcfarling
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« Reply #53 on: February 14, 2006, 04:49:39 PM »
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Isn't that self-evident?

I would say that it is definitely not self evident. I think you're saying that it's the liquid crystals themselves that are the limiting factor. Are you speculating on that or do you have any hard evidence that backs that up?
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jani
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« Reply #54 on: February 14, 2006, 05:25:07 PM »
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I would say that it is definitely not self evident. I think you're saying that it's the liquid crystals themselves that are the limiting factor. Are you speculating on that or do you have any hard evidence that backs that up?
Please re-read my original response.

I think the problem lies in controlling the crystals with the desired amount of precision.

The "hard evidence" lies in the fact that nobody appears to have made displays with better precision, and are instead concentrating on improving the backlighting.
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61Dynamic
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« Reply #55 on: February 14, 2006, 06:50:50 PM »
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The "hard evidence" lies in the fact that nobody appears to have made displays with better precision, and are instead concentrating on improving the backlighting.
[a href=\"index.php?act=findpost&pid=58170\"][{POST_SNAPBACK}][/a]

Bingo.

Since no company sells a LCD above 24-bits, there is no push for it in R&D, all new tech is in improving what we currently have and no future technologies-LCD or otherwise-are above 24-bit deductive logic applied to that hard evidence for the conclusion that 24+ bit displays are not possible. Maybe in 5 years time we'll see a push for it but not today.

(this all overlooks the simple fact that the signal going to the LCD is only 8-bit/channel and a display that can render more than that would be pointless.)

It's elementary my dear Watson.
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Delerue
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« Reply #56 on: February 15, 2006, 12:51:15 PM »
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(...)Maybe in 5 years time we'll see a push for it but not today.

Yeah. I agree with you. The same way LCD monitors today has a 24 bits, and yesterday tecnology was 18 bits.

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this all overlooks the simple fact that the signal going to the LCD is only 8-bit/channel and a display that can render more than that would be pointless.

I understand. I want know where and why exactly are the bottleneck. DVI connector? Video card output?

Thanks!
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jani
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« Reply #57 on: February 15, 2006, 01:41:20 PM »
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Yeah. I agree with you. The same way LCD monitors today has a 24 bits, and yesterday tecnology was 18 bits.
I understand. I want know where and why exactly are the bottleneck. DVI connector? Video card output?
Yes and yes; the two are of course related.

The video card must follow the DVI spec when sending signals via DVI.

I suppose it's technically possible to abuse the DVI spec's dual link option for sending more than 8 bpc.
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61Dynamic
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« Reply #58 on: February 15, 2006, 01:42:27 PM »
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I understand. I want know where and why exactly are the bottleneck. DVI connector? Video card output?

Thanks!
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It's the video card itself. Even if a card was built that was high-bit, PS would have to support it as well.
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Delerue
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« Reply #59 on: February 15, 2006, 02:37:41 PM »
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Yes and yes; the two are of course related.

The video card must follow the DVI spec when sending signals via DVI.

I suppose it's technically possible to abuse the DVI spec's dual link option for sending more than 8 bpc.
[a href=\"index.php?act=findpost&pid=58222\"][{POST_SNAPBACK}][/a]

Hmmm... So you think that the future has something to do with dual link? Or you think that they'll find another way to improve the color palette?
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