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| An expensive TV is a poor investment, and people spend FAR too much on them |
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| Zero999:
--- Quote from: tooki on February 08, 2022, 04:58:37 pm --- --- Quote from: Zero999 on February 08, 2022, 01:52:47 pm ---I don't see how adding an extra colour such as yellow, or white, especially the latter, can be a good thing for colour definition. It will increase intensity, but at the loss of colour definition, at higher intensities. --- End quote --- It’s the exact opposite: while human vision peaks at certain wavelengths, our color receptors actually have very shallow curves, meaning we are still quite sensitive to other wavelengths besides the peaks. This, together with the reflectivity characteristics of objects, is why so many physical objects look awful under RGB “white”. And while we can simulate many colors on displays with well-chosen RGB wavelengths, it’s not 100%, and yellow is one area where we are really sensitive to it being “off” because skin tones are yellows to reds. Hence Sharp’s attempt to improve color rendition with a yellow subpixel. It certainly wasn’t for brightness, since if anything, the added pixel structure reduces overall brightness. --- End quote --- The light from the TV is not used to illuminate objects. The aim is to reproduce as larger range of colours as possible, so it's more desirable to have sharp peaks from the red, green and blue emitters, to ensure they only excite the intended cones.The eye can't distinguish between spectral yellow and a mixture of red and green light, so there is no point in having a yellow emitters on the screen. |
| bw2341:
--- Quote from: tooki on February 08, 2022, 04:52:39 pm --- --- Quote from: magic on February 08, 2022, 08:59:18 am --- --- Quote from: tooki on February 08, 2022, 07:40:56 am ---It sounds to me like he thinks they’re just adding white to all the colors indiscriminately, washing it out, or that it’ll somehow reduce the available color space? --- End quote --- He says that this is what they do to exceed the brightness available from RGB pixels alone when such brightness is called for. Which doesn't sound completely implausible. Consumer technology is crappy like that and it doesn't get more consumer than TV :P --- End quote --- But that’s not what the white is for per se. It’s to offload the white component of the RGB value to a white subpixel to reduce wear on the blue subpixel. It’s not that the RGB subpixels can’t achieve the desired brightness, it’s that doing so wears out the blue subpixel faster. --- End quote --- LG's white OLED TV displays are effectively a uniform array of white OLED subpixels. A blue emissive layer is combined with an orange emissive layer to make white. Red, green and blue filter stripes are use to make the RGB subpixels, just like in an LCD TV. For the white stripes, the subpixels are simply left unfiltered. So in an overly simplistic analysis, the white subpixels are three times brighter than the red, green and blue subpixels at the same power level. My criticism of LG's design shouldn't be considered an attack. The competition between LG's OLEDs and Samsung's LCDs is excellent for consumers as they've raised picture quality and lowered prices at the same time. Still, we have to acknowledge both the advantages and disadvantages of any new technology. |
| tom66:
--- Quote from: bw2341 on February 08, 2022, 03:38:32 am ---From what I've read, LG WOLED TVs have significant image processing behind the scenes. There is a very aggressive automatic brightness limiter because of a strict power budget for the whole panel. This means that a full screen of pure white is very dim compared to pure white box in the middle of normal image. --- End quote --- This is pretty common on emissive displays. Most plasma display panels exhibited the same effect where the maximum number of sustain fields was limited by the number of set pixels. For the Pioneer Kuro, for instance, the typical ABL was about 60%, so once more than 60% of the panel was full white (or some greater proportion was grey) the panel would dim. The dimming is progressive to keep the overall power limit at a peak. You could override this in the service menu, turning the ABL threshold up to about 80%, which increased the brightness. The consequence was the set would pull about 800W on full white, and the PFC section on the PSU would occasionally chirp (possibly going into current-limit hiccup) - though with no noticeable effect on the picture as there was enough bus capacitance to hold the whole set up for way too long. I didn't run my panel long in this configuration, I was sure something would break! But, it was damn bright on full white. I'm not sure what the ABL is on a WOLED, but the effect on a plasma display was only really visible under certain situations; the film THX1138 comes to mind. And, your eyes tended to adjust reasonably quickly, so it never bothered me. |
| tooki:
--- Quote from: Zero999 on February 08, 2022, 06:31:33 pm --- --- Quote from: tooki on February 08, 2022, 04:58:37 pm --- --- Quote from: Zero999 on February 08, 2022, 01:52:47 pm ---I don't see how adding an extra colour such as yellow, or white, especially the latter, can be a good thing for colour definition. It will increase intensity, but at the loss of colour definition, at higher intensities. --- End quote --- It’s the exact opposite: while human vision peaks at certain wavelengths, our color receptors actually have very shallow curves, meaning we are still quite sensitive to other wavelengths besides the peaks. This, together with the reflectivity characteristics of objects, is why so many physical objects look awful under RGB “white”. And while we can simulate many colors on displays with well-chosen RGB wavelengths, it’s not 100%, and yellow is one area where we are really sensitive to it being “off” because skin tones are yellows to reds. Hence Sharp’s attempt to improve color rendition with a yellow subpixel. It certainly wasn’t for brightness, since if anything, the added pixel structure reduces overall brightness. --- End quote --- The light from the TV is not used to illuminate objects. The aim is to reproduce as larger range of colours as possible, so it's more desirable to have sharp peaks from the red, green and blue emitters, to ensure they only excite the intended cones.The eye can't distinguish between spectral yellow and a mixture of red and green light, so there is no point in having a yellow emitters on the screen. --- End quote --- I didn’t say TVs are used to illuminate objects. If we had absolutely perfect RGB emitters, the above theory would hold. But a) we don’t (the peaks may not be where they need to be, and in filtered subpixels, they are often impure and allow some white to “leak”), and b) yellow subpixels allowed some of the spectral yellow light from the white light sources used to be utilized to improve color rendition. I’d be curious to know why RGB LED backlighting hasn’t become widespread in LCDs, instead we create broad-spectrum white light and filter it. Sony does it in some models (“Triluminos”), but I’m not aware of others. |
| bw2341:
--- Quote from: tooki on February 08, 2022, 06:51:10 pm ---I’d be curious to know why RGB LED backlighting hasn’t become widespread in LCDs, instead we create broad-spectrum white light and filter it. Sony does it in some models (“Triluminos”), but I’m not aware of others. --- End quote --- It is very common, but not with RGB LEDs. Quantum dot enhancement film is used in front of a pure blue LED backlight. The film has a mix of red and green quantum dots that efficiently convert the blue light to narrowband red and green light. |
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