Most of the complaints in this thread deal with light
blotches in dark
images. I'm seeing a dark
blotch in certain light
images on my new Sony KDL-40XBR2, made in November 2006.
There's an irregular swath, predominantly vertical, sitting slightly to the left of the center line of the screen in roughly the top two-thirds of the image. In solid light gray test patterns it's barely visible as a slightly darker gray. It doesn't have a distinct edge or border. It grades very gradually into the uniformly lighter shades of gray to either side of it and below it.
It shows up only when the image on the screen is of a certain uniform lightness, as with certain test patterns on Digital Video Essentials
. Most actual programs' images don't reveal it. Or at least, I haven't noticed it except when the screen is basically a uniform light gray.
Despite the apparent difference in symptoms, I think the underlying cause is the same: uneven backlighting.
After further experimentation with solid gray test patterns, it now appears that my Sony's problem is more one in which there are very
faint vertical stripes on the screen (not irregular blotches as I originally supposed). They run from top to bottom of the screen. They look like the LCD panel has wavelike "ripples" in it, "crests" and "troughs." The "deepest" vertical trough is slightly left of the center of the screen. It is just slightly over-dark and also has an ultra-faint pinkish color tinge to it. Outboard from it are less-pronounced ripples or troughs that are really
hard to see.
Another way to state it is that the LCD panel seems not absolutely flat along its horizontal dimension but rather "crumpled" in the same way that a rectangular scatter rug might appear crumpled if it has gotten "bunched up" in one direction.
Yet another way to describe it is as being like an "accordion" effect.
At any rate, I no longer think my problem is the same as the "cloudy backlight" problem most posters in this thread are complaining of. Judging by the pictures that have been posted, that problem produces what look like puffs of smoke in dark images. I don't see that kind of thing on my unit.
The main defect I see is apparently called a vertical-band
or v-band mura
). Here is an image from that PDF file that looks a lot like my screen displaying a gray test pattern:
Notice the faint dark vertical stripe to the right of center. It looks like the main "trough" on mine, except that mine is to the left of center.
The type of defect most people in this thread are dealing with is probably a cluster mura