Frame/Backlight dimming on Sony R550A series-normal behavior or not? - AVS Forum
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Old 10-12-2013, 10:58 AM - Thread Starter
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I don't know if I should post this here or just jump into the official R550A thread, but this seems safer for now...

A few days ago I bought a KDL-70R550A from Costco and I need some help understanding exactly how the frame dimming feature works (or whatever it's called officially by Sony). Backlight dimming is important to me, and when shopping around I wouldn't even consider any LCD set that didn't have some form of dimming. But now I'm wondering now if I am misunderstanding what it does on this model. Sony certainly doesn't provide much information on it. I have been on the phone with Sony for over 3 hours thus far looking for a definitive answer on how the backlight dimming is supposed to work on this model, and am now waiting for a reply from engineering. After detailed explanations and some of the requisite troubleshooting steps, at least one tech support person agreed that the set was not behaving correctly and that it was defective.

So I bought a second one as a replacement, which of course is doing exactly the same thing.

Here's the behavior/problem:

I was expecting that "frame dimming" would, among other things, at least completely shut off the all of the edge LEDs when the scene was intended to be fully black. This assumption is based on the behavior of my older Sony HX800 set which behaves like this between scenes - the LCD panel goes as dark as best it can, and almost simultaneously the edge LEDs all go dark. It is a very effective feature, and very important to me as a means of hiding clouding.

I know that the 550A does not do regional dimming like the HX800 does, but I don't see why the full screen dimming behavior is implemented so differently. Between scenes on the R550A where the screen should go fully black, only the LCD panel goes dark, and I get to stare at clouding until the scene comes back up. If, and only if, the dark scene is long enough (rare), the LEDs will go out after about 6 seconds. This is way too long of a time delay for the LED backlight dimming to be effective as a means of helping to hide the distraction of clouding.

This behavior has been confirmed with other video sources (a different bluray player and my HTPC) using the AVS-HD field patterns. With a 0% field the LEDs go off after 6 seconds, and as soon as I step to 1% field (or anything appears on the screen at all, like the mouse cursor on the HTPC) the LEDs pop back on almost instantly. It's that damn 6 second delay going dark that is confounding me.

I have tried most setting combinations/permutations that I can think of. In particular, the Advanced Contrast Enhancer in the advanced picture settings must be set to something other than OFF for the LEDs to shut off at all, even after six seconds. They stay on forever with a black screen if the setting is OFF. I was surprised to see that the recommended settings by various users show Advanced Contrast Enhancer set to OFF, so I am wondering how people are seeing the benefits of dimming, if at all.

Can anyone offer any advice on this feature of the R550? If it can't shut all the backlight LEDs off during normally short black scene transitions as my HX800 does (but without the 800's zoning, of course), I can't see any possible use for it. I doesn't help at all that the clouding on the replacement set is as bad as I have ever seen.

Thanks in advance.

RogerH
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Sony Kdl 70r550a 70 Inch Led Hdtv , Sony Bravia 40 Inch Kdl40hx800 3d Ready Led Hdtv
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