peter69
23.02.2005, 12:10
http://www.extremetech.com/article2/0,1558,1734380,00.asp
neliosainen vertailu CRT, LCD, plasma, DLP ja LCoS näytöistä. Valitut laitteet ovat hiukan keskivertokuluttajista poikkeavia, mm. NEC:in 40" LCD ja 61" plasma, mutta itse vertailu on varsin kattava ja perinpohjainen. Harmi että mukana ei ole näitä yleisimpiä malleja, esimerkiksi joku Sharpin Aquos LCD ja Pioneerin tai Panasonicin 42"-50" plasma.
Täältä löytyy myös hyvät perusteet mm. näyttöjen vanhenemisesta, taustaheijastusten ja -valon vaikutuksesta jne. Oikeastaan ainoa, jossa amerikkalainen markkina eroaa suomalaisesta on loppu-conclusion eli suomalaisessa kodissa 40" CRT tuskin on vaihtoehto ;-)
Tässä yhteenvedot LCD vs. Plasma puolesta:
LCD Notable Variations and Recent Developments: The largest LCD panel currently shipping is 46 inches with a native resolution of 1920 x 1080p (Samsung). The largest size LCD prototype that has been shown is 65 inches 1920 x 1080p (Sharp). LG.Philips will be shipping a 55 inch 1920 x 1080p LCD panel in the fourth quarter of 2004 • The highest resolution LCD panel currently available is 3840 x 2400 (a 22 inch computer display) • Rear projection LCD displays are available up through a 70 inch screen size. Note that projection LCDs use a small poly-silicon based LCD chip rather than a large amorphous silicon based panel.
LCD Special issues: For LCDs the native Transfer Characteristic (the brightness or luminance for a given signal voltage applied to the panel) has an irregular "S" shape. This means that the brightness changes slowly with intensity at the ends of the gray-scale near black or peak white but changes rapidly in the middle of the gray-scale. (The graph looks like a stylized S with long legs that turn almost horizontal near the top and bottom.) The signal processing electronics has to reconfigure this behavior into a straight logarithmic (power-law) gray-scale relationship (see Part II). To do it well takes 12 or more bits of look-up tables and digital-to-analog converters. Many displays are unable to do this and that leads to a compression of the gray-scale at the bright and dark ends and to other irregularities at the dark-end • Every pixel in an LCD has control electronics on the inside of the panel that produces dark gaps between pixels. This accentuates the appearance of individual pixels and is referred to as the Screen Door Effect because of the similarity to looking through the mesh screen on a storm door. The fill factor or aperture ratio of the light emitting portion of the pixel depends on the particular LCD technology and the pixel pitch and is generally between 50 and 70 percent.
LCD Strongest Points: Direct-view LCDs produce exceptionally sharp, high contrast images, including fine text and graphics • Brightest of all the display technologies • Highest resolution of all the flat panels (but the LCD4000 is only 1280 x 768) • LCD panel intensity is controlled by an analog signal, which allows it to produce a smooth intensity-scale that is free of dithering noise and artifacts, especially at the dark-end of the scale (but most current digital signal processing implementations don't take advantage of this due to insufficient bit-depth) • Image noise resulting from poor quality video signals was less apparent due to the slower pixel response times • Low reflection of ambient light due to the panel's polarizers and color filters • The thinnest displays available and also not very heavy • Perfectly quiet for normal viewing (but on some models fans turn on at the brightest backlight settings).
LCD Weakest Points: Relatively bright black-level • Brightness and color saturation generally decrease as the viewing angle increases. Same effect also produces hue errors that increase with viewing angle • Black-level generally increases with viewing angle • Slowest response time of all the displays leads to motion flicker, smear and artifacts • Lowest pixel fill factor or aperture ratio of the technologies, which often results in visible pixelation and the Screen Door Effect due to visible gaps between pixels. Less noticeable at higher resolutions and greater viewing distances • Possible uneven light distribution from the backlight • Fixed native resolution. Rescaling required for other resolution formats.
Other LCD Artifacts: S shaped Transfer Characteristic often leads to gray-scale compression and saturation near peak white and a poor quality gray-scale near black (but not seen in the NEC LCD4000) • Variations in screen brightness and color uniformity and a slightly mottled background • Variations in the panel's analog signal response can lead to color tracking errors • Irregularities at the dark-end of the gray-scale due to insufficient signal processing bit-depth.
LCD Computer Application Viewing tests: Image and picture quality was absolutely stunning for computer applications. Images were very sharp and had the highest contrast for fine text and graphics. InfoComm ShootOut photographic images were rendered accurately when viewed face on. As the viewing angle increases brightness and color saturation decrease noticeably. This effect is much less noticeable with business graphics and text.
LCD Video Application Viewing Tests: The LCD4000 did a relatively poor job of displaying video, in part because important user and calibration controls were missing from this particular commercial model. The image had a strong blue caste with component video, but in S-Video we were able to squeeze out a tolerably good image. An external video processor would have produced excellent video image quality, inline with the computer application results discussed above.
LCD Future Trends and Commentary: LCDs are the dominant flat panel technology for computer applications. There is now a major push to try to accomplish the same thing with video. The critical factors being screen size versus cost. While LCDs are still considerably smaller and more expensive than plasma displays that gap is closing, with many analysts predicting that both will eventually turn in the LCD's favor. This is due in large part to the much larger economies of scale for LCD manufacturing, research and development. In order to capture the high-end of the video market LCDs will need to continue improving their black-levels and response times and reducing their viewing angle artifacts, which become more obvious with the spread out audiences that watch the larger screens.
Plasma Notable Variations: A number of manufacturers (Fujitsu-Hitachi, Panasonic, Samsung) have panels with significantly darker black-levels than the NEC panel, resulting in a Dynamic Range (full field Contrast) manufacturer's spec of 3000:1 or more, but that applies only to the highest peak intensity at a very low 1 percent APL value. Although black-level is very important the NEC 61XM2 has fewer overall artifacts than other panels, which is why we chose it as the reference plasma display • Pioneer has a panel that runs at 72 Hz and provides 3:3 Pulldown, which eliminates the judder found in 3:2 Pulldown displays (see Motion Artifacts in Part III).
Plasma Recent Developments: The largest shipping plasma panel is 71 inches by LG with a resolution of 1920 x 1080p. The largest prototype is 80 inches by Samsung (also with 1920 x 1080p) • Many panels are now advertising a 60,000 hour phosphor lifetime (see Display Aging).
Plasma Special issues: The Brightness spec listed for many plasma displays is the peak brightness of the bare panel without the contrast enhancing light absorbing layer, which typically reduces the brightness by about 50 percent. It's also measured for an Average Picture Level APL of only 1 percent, so the actual viewable peak brightness for typical video with 15 to 25 percent APL may be considerably less. Note that the values listed above under Primary Specs are the ones we measured for the display • The peak brightness listed for many plasma displays (500 to 1000 cd/m2) is excessively bright for most subdued ambient light viewing conditions. If you turn down the peak brightness by a factor of 2 or 3 then the Dynamic Range (full field contrast) will be reduced by the same factor.
Finding a display with a lower peak brightness should then deliver better performance (less is more). One way to accomplish this would be with a darker absorbing layer. That would maintain the specified Dynamic Range and deliver a better black-level at the same time • The power consumption of a plasma display depends on the Average Picture Level APL of the image because the average current drawn by a pixel depends on its brightness. For low APL the power consumption of a plasma display can fall by more than 50 percent from its peak value at high APL, and may be less than a comparable size LCD panel (because its power consumption doesn't vary with APL).
Plasma Strongest Points: Direct-view plasma displays produce exceptionally sharp, high contrast images, including fine text and graphics • Excellent color saturation • Widest viewing angle of all the flat panels • Some models have a very dark black-level • Very fast pixel response time • Largest direct-view display technology available • The thinnest displays available.
Plasma Weakest Points: Peak brightness and Dynamic Range (full field contrast) decreases substantially with the Average Picture Level (Part I). Generally not an issue for video that has low APLs of 15 to 25 percent • Spatial and temporal dithering produce noise and false contouring in dark images. These artifacts were more noticeable on plasma displays than on DLP displays • Pixelated image with Screen Door Effect due to noticeable gaps between pixels. Less noticeable at higher resolutions and greater viewing distances • Fixed native resolution. Rescaling required for other resolution formats • Fan Noise • Very heavy.
Other Plasma Artifacts: Possibility of long-term uneven phosphor aging • Reflects more ambient light than other technologies • When viewed from an angle, internal reflections within the panel can produce noticeable ghost images when there is a dark background • Temporary latent images may appear on some units due to charge build up, but disappear after a short time • Irregularities at the dark-end of the gray-scale due to insufficient bit-depth in signal processing.
Plasma Computer Application Viewing tests: Image and picture quality was excellent for computer applications. The variation of brightness with Average picture Level APL sometimes reduced brightness to well below that of the CRT (see Part I). When there is a switch between images it can take a noticeable fraction of a second for the display to adjust itself to the new APL. The InfoComm ShootOut photographic images were rendered accurately.
Plasma Video Application Viewing Tests: For video the picture quality was excellent. The colors were vibrant and saturated and were a good, but not a perfect match to the CRT reference, in part because Gamma and the green primary were quite different from the standard (see Part II). The black-level was occasionally quite noticeable on the NEC panel. Very bright scenes were rendered beautifully, but in dark scenes noise and contouring were quite noticeable (due in part to the low value of Gamma for the display). Performance with poor quality and noisy content was not as good as with the other display technologies.
Plasma Future Trends and Commentary: With screen sizes up to 80 inches and aggressive pricing plasmas have captured a significant share of the non-CRT video market. Resolutions were until recently mostly below High Definition, but there are now many panels in the 1365 x 768 through 1920 x 1080 range. Plasmas are a type of digital CRT so it's not surprising that they have the look and feel of a CRT. Performance has been steadily improving with size and brightness going up and black-levels and artifacts going down. The most important image quality issue is reducing image noise through improved spatial and temporal dithering algorithms and signal processing. The real question is how plasma displays will hold up to the challenge from direct-view LCD panels.
neliosainen vertailu CRT, LCD, plasma, DLP ja LCoS näytöistä. Valitut laitteet ovat hiukan keskivertokuluttajista poikkeavia, mm. NEC:in 40" LCD ja 61" plasma, mutta itse vertailu on varsin kattava ja perinpohjainen. Harmi että mukana ei ole näitä yleisimpiä malleja, esimerkiksi joku Sharpin Aquos LCD ja Pioneerin tai Panasonicin 42"-50" plasma.
Täältä löytyy myös hyvät perusteet mm. näyttöjen vanhenemisesta, taustaheijastusten ja -valon vaikutuksesta jne. Oikeastaan ainoa, jossa amerikkalainen markkina eroaa suomalaisesta on loppu-conclusion eli suomalaisessa kodissa 40" CRT tuskin on vaihtoehto ;-)
Tässä yhteenvedot LCD vs. Plasma puolesta:
LCD Notable Variations and Recent Developments: The largest LCD panel currently shipping is 46 inches with a native resolution of 1920 x 1080p (Samsung). The largest size LCD prototype that has been shown is 65 inches 1920 x 1080p (Sharp). LG.Philips will be shipping a 55 inch 1920 x 1080p LCD panel in the fourth quarter of 2004 • The highest resolution LCD panel currently available is 3840 x 2400 (a 22 inch computer display) • Rear projection LCD displays are available up through a 70 inch screen size. Note that projection LCDs use a small poly-silicon based LCD chip rather than a large amorphous silicon based panel.
LCD Special issues: For LCDs the native Transfer Characteristic (the brightness or luminance for a given signal voltage applied to the panel) has an irregular "S" shape. This means that the brightness changes slowly with intensity at the ends of the gray-scale near black or peak white but changes rapidly in the middle of the gray-scale. (The graph looks like a stylized S with long legs that turn almost horizontal near the top and bottom.) The signal processing electronics has to reconfigure this behavior into a straight logarithmic (power-law) gray-scale relationship (see Part II). To do it well takes 12 or more bits of look-up tables and digital-to-analog converters. Many displays are unable to do this and that leads to a compression of the gray-scale at the bright and dark ends and to other irregularities at the dark-end • Every pixel in an LCD has control electronics on the inside of the panel that produces dark gaps between pixels. This accentuates the appearance of individual pixels and is referred to as the Screen Door Effect because of the similarity to looking through the mesh screen on a storm door. The fill factor or aperture ratio of the light emitting portion of the pixel depends on the particular LCD technology and the pixel pitch and is generally between 50 and 70 percent.
LCD Strongest Points: Direct-view LCDs produce exceptionally sharp, high contrast images, including fine text and graphics • Brightest of all the display technologies • Highest resolution of all the flat panels (but the LCD4000 is only 1280 x 768) • LCD panel intensity is controlled by an analog signal, which allows it to produce a smooth intensity-scale that is free of dithering noise and artifacts, especially at the dark-end of the scale (but most current digital signal processing implementations don't take advantage of this due to insufficient bit-depth) • Image noise resulting from poor quality video signals was less apparent due to the slower pixel response times • Low reflection of ambient light due to the panel's polarizers and color filters • The thinnest displays available and also not very heavy • Perfectly quiet for normal viewing (but on some models fans turn on at the brightest backlight settings).
LCD Weakest Points: Relatively bright black-level • Brightness and color saturation generally decrease as the viewing angle increases. Same effect also produces hue errors that increase with viewing angle • Black-level generally increases with viewing angle • Slowest response time of all the displays leads to motion flicker, smear and artifacts • Lowest pixel fill factor or aperture ratio of the technologies, which often results in visible pixelation and the Screen Door Effect due to visible gaps between pixels. Less noticeable at higher resolutions and greater viewing distances • Possible uneven light distribution from the backlight • Fixed native resolution. Rescaling required for other resolution formats.
Other LCD Artifacts: S shaped Transfer Characteristic often leads to gray-scale compression and saturation near peak white and a poor quality gray-scale near black (but not seen in the NEC LCD4000) • Variations in screen brightness and color uniformity and a slightly mottled background • Variations in the panel's analog signal response can lead to color tracking errors • Irregularities at the dark-end of the gray-scale due to insufficient signal processing bit-depth.
LCD Computer Application Viewing tests: Image and picture quality was absolutely stunning for computer applications. Images were very sharp and had the highest contrast for fine text and graphics. InfoComm ShootOut photographic images were rendered accurately when viewed face on. As the viewing angle increases brightness and color saturation decrease noticeably. This effect is much less noticeable with business graphics and text.
LCD Video Application Viewing Tests: The LCD4000 did a relatively poor job of displaying video, in part because important user and calibration controls were missing from this particular commercial model. The image had a strong blue caste with component video, but in S-Video we were able to squeeze out a tolerably good image. An external video processor would have produced excellent video image quality, inline with the computer application results discussed above.
LCD Future Trends and Commentary: LCDs are the dominant flat panel technology for computer applications. There is now a major push to try to accomplish the same thing with video. The critical factors being screen size versus cost. While LCDs are still considerably smaller and more expensive than plasma displays that gap is closing, with many analysts predicting that both will eventually turn in the LCD's favor. This is due in large part to the much larger economies of scale for LCD manufacturing, research and development. In order to capture the high-end of the video market LCDs will need to continue improving their black-levels and response times and reducing their viewing angle artifacts, which become more obvious with the spread out audiences that watch the larger screens.
Plasma Notable Variations: A number of manufacturers (Fujitsu-Hitachi, Panasonic, Samsung) have panels with significantly darker black-levels than the NEC panel, resulting in a Dynamic Range (full field Contrast) manufacturer's spec of 3000:1 or more, but that applies only to the highest peak intensity at a very low 1 percent APL value. Although black-level is very important the NEC 61XM2 has fewer overall artifacts than other panels, which is why we chose it as the reference plasma display • Pioneer has a panel that runs at 72 Hz and provides 3:3 Pulldown, which eliminates the judder found in 3:2 Pulldown displays (see Motion Artifacts in Part III).
Plasma Recent Developments: The largest shipping plasma panel is 71 inches by LG with a resolution of 1920 x 1080p. The largest prototype is 80 inches by Samsung (also with 1920 x 1080p) • Many panels are now advertising a 60,000 hour phosphor lifetime (see Display Aging).
Plasma Special issues: The Brightness spec listed for many plasma displays is the peak brightness of the bare panel without the contrast enhancing light absorbing layer, which typically reduces the brightness by about 50 percent. It's also measured for an Average Picture Level APL of only 1 percent, so the actual viewable peak brightness for typical video with 15 to 25 percent APL may be considerably less. Note that the values listed above under Primary Specs are the ones we measured for the display • The peak brightness listed for many plasma displays (500 to 1000 cd/m2) is excessively bright for most subdued ambient light viewing conditions. If you turn down the peak brightness by a factor of 2 or 3 then the Dynamic Range (full field contrast) will be reduced by the same factor.
Finding a display with a lower peak brightness should then deliver better performance (less is more). One way to accomplish this would be with a darker absorbing layer. That would maintain the specified Dynamic Range and deliver a better black-level at the same time • The power consumption of a plasma display depends on the Average Picture Level APL of the image because the average current drawn by a pixel depends on its brightness. For low APL the power consumption of a plasma display can fall by more than 50 percent from its peak value at high APL, and may be less than a comparable size LCD panel (because its power consumption doesn't vary with APL).
Plasma Strongest Points: Direct-view plasma displays produce exceptionally sharp, high contrast images, including fine text and graphics • Excellent color saturation • Widest viewing angle of all the flat panels • Some models have a very dark black-level • Very fast pixel response time • Largest direct-view display technology available • The thinnest displays available.
Plasma Weakest Points: Peak brightness and Dynamic Range (full field contrast) decreases substantially with the Average Picture Level (Part I). Generally not an issue for video that has low APLs of 15 to 25 percent • Spatial and temporal dithering produce noise and false contouring in dark images. These artifacts were more noticeable on plasma displays than on DLP displays • Pixelated image with Screen Door Effect due to noticeable gaps between pixels. Less noticeable at higher resolutions and greater viewing distances • Fixed native resolution. Rescaling required for other resolution formats • Fan Noise • Very heavy.
Other Plasma Artifacts: Possibility of long-term uneven phosphor aging • Reflects more ambient light than other technologies • When viewed from an angle, internal reflections within the panel can produce noticeable ghost images when there is a dark background • Temporary latent images may appear on some units due to charge build up, but disappear after a short time • Irregularities at the dark-end of the gray-scale due to insufficient bit-depth in signal processing.
Plasma Computer Application Viewing tests: Image and picture quality was excellent for computer applications. The variation of brightness with Average picture Level APL sometimes reduced brightness to well below that of the CRT (see Part I). When there is a switch between images it can take a noticeable fraction of a second for the display to adjust itself to the new APL. The InfoComm ShootOut photographic images were rendered accurately.
Plasma Video Application Viewing Tests: For video the picture quality was excellent. The colors were vibrant and saturated and were a good, but not a perfect match to the CRT reference, in part because Gamma and the green primary were quite different from the standard (see Part II). The black-level was occasionally quite noticeable on the NEC panel. Very bright scenes were rendered beautifully, but in dark scenes noise and contouring were quite noticeable (due in part to the low value of Gamma for the display). Performance with poor quality and noisy content was not as good as with the other display technologies.
Plasma Future Trends and Commentary: With screen sizes up to 80 inches and aggressive pricing plasmas have captured a significant share of the non-CRT video market. Resolutions were until recently mostly below High Definition, but there are now many panels in the 1365 x 768 through 1920 x 1080 range. Plasmas are a type of digital CRT so it's not surprising that they have the look and feel of a CRT. Performance has been steadily improving with size and brightness going up and black-levels and artifacts going down. The most important image quality issue is reducing image noise through improved spatial and temporal dithering algorithms and signal processing. The real question is how plasma displays will hold up to the challenge from direct-view LCD panels.