Dark room luminance target for flat-panel LED-LCDs: Should it ever be less than 30-40 fL? - AVS Forum
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post #1 of 7 Old 09-23-2012, 03:11 PM - Thread Starter
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Like the title suggests, is it ever a good idea to set luminance (via backlight) lower than 30-40 fL for a dark room on a flat-panel LED-LCD? Such as when not using a bias light and having no ambient light? Or when sitting close to a large screen? If so, what values should be targeted?
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post #2 of 7 Old 09-23-2012, 04:09 PM
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My projector outputs is about 25fl with the HP screen and I need bias lighting to prevent my eyes from hurting. My screen size is only 65" diag so it might as well be a flat panel. User you own comfort as a guide, but probably the 14fl that is rule of thumb for projection would be a starting point to shoot for.
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post #3 of 7 Old 09-24-2012, 01:33 PM
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All you are trying to do with peak white level is to avoid clipping whenever possible and to avoid eyestrain. If you know when your display clips white (some never clip white at ANY Contrast setting) your only concern is eyestrain. Eyestrain comes from viewing the bright screen against a black background. If you sit so close to the screen you can't see any black around it, you can make the screen as bright as you like without ever having eyestrain issues. The more black there is around the screen within your field of view, the more likely you will be to have eyestrain issues and the dimmer you'll want to set the TV. Sit closer so there's less black area around the TV and you'll decrease the possibility of eyestrain.

Setting the Backlight is actually more important for BLACK LEVEL than it is for 100% white.. maybe. LCD displays aren't particularly impressive in regards to blak level. To get the best black level, you want to find the lowest possible backlight setting where the backlight doesn't mis-behave (gives poor color or odd motion effects). When you find the dimmest setting for Backlight where the display produces good/accurate images, set the Contrast control to achieve the peak white level you need. This method helps you achieve the lowest possible black level. If the TV won't get bright enough with the Contrast control (or if clipping of one or all 3 colors) sets-in when you try to use Contrast to set peak white, your only choice will be to raise the backlight setting, but you still want to try to keep it as low as you can to achieve the peak white level you need.

There is no 1 right number for peak white... "it depends" is the only right answer. The farther you sit from the TV, the more likely you'll need a lower setting (30 fL or less). The closer you sit, the less critical the peak white level becomes. Wen you sit too far away, you can't see all the detail in 1080 images also... and WAY too many people sit WAY too far from their 1080 displays to be able to see all the detail in images. six feet for a 50" panel is just about the sweet-spot, but I'd guess the average distance people sit from 50" panels is closer to 9 feet so they aren't seeing all the detail the picture has to offer.

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post #4 of 7 Old 09-24-2012, 11:18 PM
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Quote:
Originally Posted by Doug Blackburn View Post

and WAY too many people sit WAY too far from their 1080 displays to be able to see all the detail in images. six feet for a 50" panel is just about the sweet-spot, but I'd guess the average distance people sit from 50" panels is closer to 9 feet so they aren't seeing all the detail the picture has to offer.

... intentionally so, in my case. smile.gif ~9ft from a 42" display ... all the better to hide all the artyfacts in my so-called 1080i/p "HD"TV source materials. Let's not delude ourselves into thinking that anything other than an extremely well mastered BD has anything close to "all the detail the picture has to offer." For most of the (TV) viewing public, HDTV is just an empty promise that will never be fulfilled. There's no point in torturing ourselves. smile.gif
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post #5 of 7 Old 10-09-2012, 10:59 AM
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I have a related question: when calibrating LCD/LED displays should I use the field test patterns rather than the windows for setting peak luminance and for calibrating grayscale? I tried to calibrate a 55" Samsung ES6800 LED yesterday and couldn't get peak luminance higher than 22 ftL in Movie mode with the backlight and contrast cranked up all the way. It was only in Standard mode that I was able to hit 30 ftL. Unfortunately, I didn't go back and check if white clipping was happening and I also didn't check the backlight setting's effect on black level. Gonna have to go back re-calibrate the set....
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post #6 of 7 Old 10-09-2012, 11:08 AM - Thread Starter
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Originally Posted by daMaster View Post

I have a related question: when calibrating LCD/LED displays should I use the field test patterns rather than the windows for setting peak luminance and for calibrating grayscale? I tried to calibrate a 55" Samsung ES6800 LED yesterday and couldn't get peak luminance higher than 22 ftL in Movie mode with the backlight and contrast cranked up all the way. It was only in Standard mode that I was able to hit 30 ftL. Unfortunately, I didn't go back and check if white clipping was happening and I also didn't check the backlight setting's effect on black level. Gonna have to go back re-calibrate the set....

sounds like auto-dimming or some energy saving/eco sensor feature is on... there's no way that set can only put out 22 fL in Movie mode (assuming LED motion plus is off and so are any picture enhancements and 'eco solution' features)
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post #7 of 7 Old 10-09-2012, 01:56 PM
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I use fields on LED/LCD. Using windows on an LCD could have the opposite effect of plasmas where the auto-dimming or local dimming could reduce the brightness of white. With the backlight and contrast at 100, you should be over 60fL.
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