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Contrast ratio of LCD monitors
HEMI-Powered wrote:
Shon Kei Picture company added these comments in the current discussion du jour ... Victek wrote: I'm wondering about the contrast ratio spec of new LCD monitors. It varies between 1,000 and 3,000 in many cases, but with the screens all lined up and displaying images in the store I don't see much difference. Any opinions about how much difference this makes in the real world, and how you can actually assess the difference? There are only a few LCD screen manufacturers in world capable of producing a monitor with CMYK colour gamut. You can however use a cheap monitor and provided you follow a few pointers, only ever miss out of the last section of black on a contrast wedge. Although these monitors all seem to come with a 15 pin VGA plug (or adaptor) DVI (Digital Video Input) will absolutely improve the contrast range you can see on screen. I've got a 21" and a 26" Samsung monitor and also an ATI Radeon video card. I don't at all like the digital interface even if it is marginally sharper because it doesn't allow the various controls on the monitor to alter the image. Yes, this can be done with the video card but then one is altering the actual video signal at the source rather than how the monitor processes and displays it. I much prefer to run on the analog side. If you use a RADEON video card, it comes natively with built in monitor profiling adjustments. All you need to do is get the RGB examples right and you have very good colour balance without profiling the screen. This is definitely not true in my experience. I've set up both my Samsungs, one on analog and one on digital, and ran through the calibration stuff that comes with the Radeon card and with the color calibration tool Samsung provides. It is not at all a trivial task to get these things to display what I know is the correct brightness/contrast and color balance. Worse, similar settings display entirely differently on each monitor making it even more problematical to decide what "right" is. You may need a cheap program called "power strip" to move the gamma to a low contrast region suitable for photographs but once you have done these things, a $200 LG monitor will start to look like a high end Ezio. The contrast ratio described by LCD makers is all useless. I have a 2000:1 CR screen that looks no better and no worse than the $1900 Ezio I bought for editing photos - most of the time. I use the (wide screen) LG for movie editing but I'd happily use it for photo editing if I didn't have the Ezio. Samsung make a screen now they claim will match the CMYK of a web offset press. Big deal. So will my tweaked LG and it cost less than half the price of the Samsung. Use power strip. The shareware version will nag you at boot but otherwise it works a treat on Samsungs |
#12
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Contrast ratio of LCD monitors
Victek wrote:
I'm wondering about the contrast ratio spec of new LCD monitors. It varies between 1,000 and 3,000 in many cases, but with the screens all lined up and displaying images in the store I don't see much difference. Any opinions about how much difference this makes in the real world, and how you can actually assess the difference? I wonder if someone who knows about densities and prints might care to comment on this. I'm too rusty! Is a 1000:1 range the same as a density range of 3.0? What is the best that prints can achieve? I would have expected less than 3.0, and if so presumably the blacks are compressed a little to fit the available dynamic range of the print? I remember sometimes having to do dodging and burning to produce the "best" black-and-white print. I have been disappointed with the LINEAR dynamic range of typical (i.e. inexpensive) LCD monitors - there is very little display of the lower blacks so that, if you have an image of 0..255, all levels below 8 may appear as one black. To get the best visible greyscale reproduction, I have found that you typically need to decrease the contrast (gain) setting, and increased the brightness (offset) setting, so that the blacks are actually shown as dark greys. This then works well with colour images. Note that I print very little, so matching monitor to printer isn't an issue for me. Perhaps these new OLED displays are better? David |
#13
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Contrast ratio of LCD monitors
saycheez wrote:
The current issue of Maximum PC reviews this subject. There are also some comments in an interview in the current issue of CPU that give insight into why LCD television panels are not what they seem compared to Plasma, DLP and particularly the late CRT, still the standard of measure. This is particularly so with regard to what contrast ratio means: if LCD panels cannot display absolute black then what does contrast ratio really mean? It is supposed to mean the ratio of lowest to brightest light. If they could display absolute black, the ratio would be infinite. Even CRTs don't have an infinite contrast ratio, as long as they have been on recently, or been in a lighted room, because of phosphorescence. Anything over 500:1 is perfectly adequate for previewing photo material meant for halftone printing or photo printing on paper. It may no be adequate for images destined for transparencies or better electronic displays. Doug McDonald |
#14
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Contrast ratio of LCD monitors
Don Stauffer in Minnesota added these comments in the current
discussion du jour ... In the end, I think this is a highly subjective issue. I'm not talking about sharpness though, I'm talking about contrast graduations. Keep in mind the human eye can only perceive a 2% contrast ratio change. To the extent this is true, why would one pay more if they can't see the difference? Following that kind of logic would also suggest that using more mega pixels really doesn't equate to better pictures. Personally, I'm not at all interested in the theoretical only the practical, so when shopping for a monitor I look to see if they look good to me and only then ask about the specs. -- HP, aka Jerry Don't be a fop or a blooter, make only pithy comments on Usenet |
#15
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Contrast ratio of LCD monitors
Check out Sony's 1000000:1 OLED screen and you will see the difference.
Toby "Victek" wrote in message ... I'm wondering about the contrast ratio spec of new LCD monitors. It varies between 1,000 and 3,000 in many cases, but with the screens all lined up and displaying images in the store I don't see much difference. Any opinions about how much difference this makes in the real world, and how you can actually assess the difference? |
#16
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Contrast ratio of LCD monitors
I'm wondering about the contrast ratio spec of new LCD
monitors. It varies between 1,000 and 3,000 in many cases, but with the screens all lined up and displaying images in the store I don't see much difference. Any opinions about how much difference this makes in the real world, and how you can actually assess the difference? If you were looking at a low key images side by side you may notice a slight difference between a monitor with a low contrast ratio and one with a high one, but to be honest 1000:1 isn't low at all. Please see my reply to the OP first, but I would disagree that 1000:1 isn't pretty low. But, unless one is into technical lab testing to glean some scientific comparisons, it is vitally important to view real world images and not just the canned displays in the stores. In my shopping this spring I found the 1000:1 displays were the lowest end monitors with the least sharp display while the 5000:1 were barely better than the 3000:1 but usually 2X-3X the price. In the end, I think this is a highly subjective issue. It occurred to me to check out the specs of the 19" flat panel I'm currently using. It's a couple of years old - contrast ratio is 500:1 and response time is 16ms. These specs are poor by today's standards yet this monitor is perfectly adequate for me. It's a good example of how specs can suggest differences that don't matter in the real world (at least not to everyone under all circumstances). |
#17
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Contrast ratio of LCD monitors
"Victek" writes:
You anticipated and answered my next question about DVI. My video card (Nvidia 6600GT) has both VGA and DVI connectors. I'm currently using the VGA connector, but the new screen I picked up has both so I will invest in a DVI cable. I don't know if the Nvidia card has the built-in monitor profiling you mentioned (?) I've read that using DVI eliminates screen centering issues - is that true? The main point of a DVI connection is it delivers fully digital data from the graphics card directly to the controller in the monitor, eliminating several sources of noise and error. With an analog connection, the digital RGB values stored in the graphics card are converted to analog RGB values via a digital to analog converter, with one pixel following another at a rate determined by an internal oscillator in the graphics card. These signals, plus a small amount of noise and hum picked up along the way, are fed to the analog input of the monitor. This circuitry has the job of guessing what resolution the graphics card is working at by looking at the sync frequencies. Then it tries to generate a local pixel clock oscillator which is as close as possible to being in sync with the one in the graphics card. An analog to digital converter converts the voltages in the input signal back into RGB values, and those are stored in the monitor's local RAM which is used to update the individual pixels in the display panel. In a perfect world, the data in the monitor would be a perfect reconstruction of what was in the graphics card, but in the real world there are black level and gain errors, noise, and clock rate mismatches. The DVI connection avoids all the analog stages, sending clock and RGB intensity data in digital form across the cable. Dave |
#18
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Contrast ratio of LCD monitors
"David J Taylor" writes:
I wonder if someone who knows about densities and prints might care to comment on this. I'm too rusty! Is a 1000:1 range the same as a density range of 3.0? Yes, it ought to be, since density is base-10 logarithm. On the other hand, you need to check what you're comparing. Some monitors are specifying a "dynamic contrast" rating that includes dimming the backlight in dark scenes. What you want to know is the largest contrast available *within one image at the same time*. Even then, this depends on the test pattern. What is the best that prints can achieve? I would have expected less than 3.0, and if so presumably the blacks are compressed a little to fit the available dynamic range of the print? I remember sometimes having to do dodging and burning to produce the "best" black-and-white print. If I remember correctly, the density range of good B&W paper developed to have good blacks, and with a glossy surface, is about 100:1, maybe 200:1 in the very best cases. Colour prints are more like 30:1. You can choose paper contrast during printing to make tradeoffs between reproducing a relatively small scene brightness range (5-6 stops) with normal contrast, or a wider scene range with lower than normal contrast. Dodging and burning in provide local exposure changes to "push" highlights and shadows towards midtone. You can even use multiple exposures on vari-contrast paper in combination with masking/dodging/burning to print different areas with different contrast. I have been disappointed with the LINEAR dynamic range of typical (i.e. inexpensive) LCD monitors - there is very little display of the lower blacks so that, if you have an image of 0..255, all levels below 8 may appear as one black. To get the best visible greyscale reproduction, I have found that you typically need to decrease the contrast (gain) setting, and increased the brightness (offset) setting, so that the blacks are actually shown as dark greys. This then works well with colour images. Note that I print very little, so matching monitor to printer isn't an issue for me. That might be deliberate on the part of the LCD makers. Pulling the darkest tones to blacks causes the rest of the tonal scale to have higher contrast and more saturated colours. Less accurate, but a lot of people like the effect. Dave |
#19
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Contrast ratio of LCD monitors
Dave Martindale wrote:
"David J Taylor" writes: I wonder if someone who knows about densities and prints might care to comment on this. I'm too rusty! Is a 1000:1 range the same as a density range of 3.0? Yes, it ought to be, since density is base-10 logarithm. On the other hand, you need to check what you're comparing. Some monitors are specifying a "dynamic contrast" rating that includes dimming the backlight in dark scenes. What you want to know is the largest contrast available *within one image at the same time*. Even then, this depends on the test pattern. Agreed. If I remember correctly, the density range of good B&W paper developed to have good blacks, and with a glossy surface, is about 100:1, maybe 200:1 in the very best cases. Colour prints are more like 30:1. You can choose paper contrast during printing to make tradeoffs between reproducing a relatively small scene brightness range (5-6 stops) with normal contrast, or a wider scene range with lower than normal contrast. Dodging and burning in provide local exposure changes to "push" highlights and shadows towards midtone. You can even use multiple exposures on vari-contrast paper in combination with masking/dodging/burning to print different areas with different contrast. Thanks for the reminder! I have been disappointed with the LINEAR dynamic range of typical (i.e. inexpensive) LCD monitors - there is very little display of the lower blacks so that, if you have an image of 0..255, all levels below 8 may appear as one black. To get the best visible greyscale reproduction, I have found that you typically need to decrease the contrast (gain) setting, and increased the brightness (offset) setting, so that the blacks are actually shown as dark greys. This then works well with colour images. Note that I print very little, so matching monitor to printer isn't an issue for me. That might be deliberate on the part of the LCD makers. Pulling the darkest tones to blacks causes the rest of the tonal scale to have higher contrast and more saturated colours. Less accurate, but a lot of people like the effect. Dave Thanks for your reply, Dave. Perhaps there is also some problem about reproducing dark very greys accurately, so the monitors are designed not to reproduce them at all? I would much prefer accuracy to the garish results sometimes seen. From what I hear, I may be in the market for the OLED displays.... Cheers, David |
#20
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Contrast ratio of LCD monitors
Don Stauffer in Minnesota wrote:
[] The figures I had seen said 2% for the blackest black on fully exposed printing paper. This corresponds well to about the same value for 3M Black Velvet paint. I believe inks from printing press are a bit more reflective. I worked on a project developing blacks for sunshades on satellite optical instruments. It was hard to find ANYTHING blacker than 1%. The best blacks we had were between 1 and 2%. Thanks, Don. I recall that for TV test targets they once used recessed boxes (sort of a light sink) lined with black baize to try and get a very low reflectivity value. However, all this doesn't explain why LCD monitors, with claimed contrast ratios well in excess of 100:1, can produce such lousy dark greyscales! Cheers, David |
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