LED Backlighting, Local Dimming and Power Consumption...

Idjiit · 09-27-07, 05:43 PM

In theory, one of the great advantages with locally dimmed backlighting is that it can be very power efficient since it is only expending light energy for areas that need it most. I decided to put that theory to test with my Samsung LN-T4081f - here's the rather unscientific results. I'll try to do more lengthy testing over the next week or so.

To test, I had my TV setup with my usual viewing settings for cable TV (4:3, SD, non-digital) and for use with my Apple TV, which I use throughout the day as a music player while I'm working. The figures here are just in watts - what the TV is drawing in power.

Code:

Power Saving/LED Scan        		| OFF | low | med |  hi | aut | LED Scanning    
_________________________________________________________________
SDTV - Backlight 4, LD ON		| 112 |  97 |  90 |  85 | 112 | 112
SDTV - Backlight 4, LD OFF		| 148 | 130 | 114 | 105 | 146 | 146
"Searching for Signal" BL 3 		|  64 |  63 |  57 |  55 |  62 |  64
Apple TV, Album View, BL3 LD ON		|  88 |  84 |  79 |  75 |  91 |  93
Apple TV, Album View, BL3 LD OFF	| 134 | 121 | 109 | 102 | 133 | 145
Apple TV, Album View, BL10 LD ON	| 135 | 113 |  89 |  81 | 135 | 98
Apple TV, Album View, BL10 LD OFF	| 222 | 176 | 138 | 113 | 222 | 144

Needless to say, the consumption savings with local dimming are pretty obvious.

Gotta run... will try to fill in details later.

GrantR · 09-27-07, 06:05 PM

Nice power savings with LD on

Another important test to do: what's the power consumption when the TV is off/standby? It should be under 1W if they're doing it properly.

Idjiit · 09-27-07, 06:34 PM

Yeah, off its basically 0 - hits 1 periodically.

GrantR · 09-28-07, 10:14 AM

It's interesting to compare that info to a Cnet page they recently posted comparing 54 hdtvs for power usage.

http://reviews.cnet.com/4520-6475_7-...3.html?tag=arw

It turns out most LCDs use around 0.30 watts per square inch, once they're calibrated to a reasonable brightness. When you have your 81 tuned to a backlight of 10 with LD off, it's producing 0.32 W/in^2, so that's pretty normal. With lesser backlights and still LD off, it's down to 0.20 W/in^2. But with LD on it's down to 0.16 W/in^2. that's about half the power use of a regular non LD LCD!

RPTVs use about 0.15 W/in^2 too, so this technology is just as efficient, now. Plasmas and CRTs seem to be a hint over 0.30 W/in^2 also.

Idjiit · 10-01-07, 10:13 AM

Yeah, I'd seen that page - thanks for running the numbers, it's a very interesting comparison. For what it's worth, the setting I've settled on for now with the Apple TV is Backlight at 5, Power Saving at Low, LD on.

09-27-07, 05:43 PM	#1 \| Link	<a href='http://rev.avsforum.com/phpAdsNew/adclick.php?n=a4ac4393' target='_blank'><img src='http://rev.avsforum.com/phpAdsNew/adview.php?what=zone:30&n=a4ac4393' border='0' alt=''></a>
Idjiit Member Join Date: Oct 2006 Posts: 189	LED Backlighting, Local Dimming and Power Consumption... In theory, one of the great advantages with locally dimmed backlighting is that it can be very power efficient since it is only expending light energy for areas that need it most. I decided to put that theory to test with my Samsung LN-T4081f - here's the rather unscientific results. I'll try to do more lengthy testing over the next week or so. To test, I had my TV setup with my usual viewing settings for cable TV (4:3, SD, non-digital) and for use with my Apple TV, which I use throughout the day as a music player while I'm working. The figures here are just in watts - what the TV is drawing in power. Code: Power Saving/LED Scan \| OFF \| low \| med \| hi \| aut \| LED Scanning _________________________________________________________________ SDTV - Backlight 4, LD ON \| 112 \| 97 \| 90 \| 85 \| 112 \| 112 SDTV - Backlight 4, LD OFF \| 148 \| 130 \| 114 \| 105 \| 146 \| 146 "Searching for Signal" BL 3 \| 64 \| 63 \| 57 \| 55 \| 62 \| 64 Apple TV, Album View, BL3 LD ON \| 88 \| 84 \| 79 \| 75 \| 91 \| 93 Apple TV, Album View, BL3 LD OFF \| 134 \| 121 \| 109 \| 102 \| 133 \| 145 Apple TV, Album View, BL10 LD ON \| 135 \| 113 \| 89 \| 81 \| 135 \| 98 Apple TV, Album View, BL10 LD OFF \| 222 \| 176 \| 138 \| 113 \| 222 \| 144 Needless to say, the consumption savings with local dimming are pretty obvious. Gotta run... will try to fill in details later.

10-01-07, 10:13 AM	#5 \| Link	<a href='http://rev.avsforum.com/phpAdsNew/adclick.php?n=a591f81a' target='_blank'><img src='http://rev.avsforum.com/phpAdsNew/adview.php?what=zone:36&n=a591f81a' border='0' alt=''></a>
Idjiit Member Join Date: Oct 2006 Posts: 189	Yeah, I'd seen that page - thanks for running the numbers, it's a very interesting comparison. For what it's worth, the setting I've settled on for now with the Apple TV is Backlight at 5, Power Saving at Low, LD on.

09-27-07, 06:05 PM	#2 \| Link
GrantR Member Join Date: Jan 2002 Location: Wellesley, MA Posts: 187	Nice power savings with LD on Another important test to do: what's the power consumption when the TV is off/standby? It should be under 1W if they're doing it properly.

09-27-07, 06:34 PM	#3 \| Link
Idjiit Member Join Date: Oct 2006 Posts: 189	Yeah, off its basically 0 - hits 1 periodically.

09-28-07, 10:14 AM	#4 \| Link
GrantR Member Join Date: Jan 2002 Location: Wellesley, MA Posts: 187	It's interesting to compare that info to a Cnet page they recently posted comparing 54 hdtvs for power usage. http://reviews.cnet.com/4520-6475_7-...3.html?tag=arw It turns out most LCDs use around 0.30 watts per square inch, once they're calibrated to a reasonable brightness. When you have your 81 tuned to a backlight of 10 with LD off, it's producing 0.32 W/in^2, so that's pretty normal. With lesser backlights and still LD off, it's down to 0.20 W/in^2. But with LD on it's down to 0.16 W/in^2. that's about half the power use of a regular non LD LCD! RPTVs use about 0.15 W/in^2 too, so this technology is just as efficient, now. Plasmas and CRTs seem to be a hint over 0.30 W/in^2 also.