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.


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.

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.

Yeah, off its basically 0 - hits 1 periodically.

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_7-6400401-3.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.

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.