Backlighting and Dimming Discussion Thread - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 2 Old 05-07-2013, 09:00 PM - Thread Starter
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Instead of having this debate scattered about in threads for different makes and models of HDTVs, I thought it would be a good idea to keep this in one place. I would like to start this thread with an issue which has been hindering my decision-making over the past week or two--the known types of LED backlighting and dimming.

Direct LED backlighting uses LEDs throughout the panel. Edge LED backlighting uses LEDs along the sides or top and bottom of the panel. With edge LED backlighting, a diffuser is used to reflect the light where there are no LEDs.

Frame dimming analyzes the general picture and adjusts the backlight level in large, general areas of the panel. Local dimming analyzes different areas of the picture and adjusts specific areas of the backlight level accordingly.

Just so you know, I got my info from Consumer Reports and Tech Radar. This is how I understand it.

Regarding backlighting, which can be viewed from more angles--edge LED with the defuser, or direct LED?

Regarding dimming, I can't understand why you'd have local dimming with edge LED backlighting, or frame dimming with direct LED backlighting. To me, that sounds like an upsidedown approach.
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post #2 of 2 Old 05-08-2013, 03:10 AM
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I can only speak for my own experience with a Sharp Quattron 3D 70" set, which is edge-lit.
The backlight shuts down when there is no signal and this feature cannot be turned off.
It is great when going between screens, but is a bit of a bother when credits are rolling and there
are blank spaces between sections -- the backlighting is more apparent when it isn't continuous in this case.
Some of the bigger Sharps use direct backlight -- maybe all the 80" and 90", but none have local dimming.
Users of other brands, with zoned backlighting, report problems of halos and bloom around bright objects
on a dark background. This will be inherent in the design until backlights are the same pixel size as the screen.
All LCD TVs use diffusers to transmit the light to the front of the screen and all LCDs have light leakage.
Different brands make different compromises of brightness, color gamut, and range of viewing angles.
I like my 70" edge-lit set except for the aforementioned backlight switching during credits. I have not had the
problems inherent in this technology; namely, flashlighting and clouding. The little I have seen is preferable to
the halo and blooming effect of zone dimming, at least for my tastes...
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