Video Asylum

Posted by Larry I (A) on March 11, 2010 at 17:04:25

In Reply to: RE: Weren't CRTs subject to geometry problems? posted by Russell on March 11, 2010 at 13:53:28

A lot of the problems with curves and lack of focus at the edges of the screen had to do with the public's desire for a flat screen and shallow depth to the set. Ideally, the electron gun at the back of the CRT should be sweeping out a perfectly consistent arc from edge to edge. Flatten out the screen and it is clear that at the center of the screen the electron beam is at 90 degrees to the screen and is illuminating a perfectly round and small spot. At the edge, however it is now hitting at an oblique angle so the spot is no longer round and small (detail is lost). This problem is MUCH worse if the screen is not only flattened out, but the gun has to sit closer to the screen (to keep the depth of the CRT shallow).

A friend had a 36" XBR that looked really good. One would think that as time went on, technology would improve the picture, but, models made a few years later actually looked substantially worse because of the drive to make flatter and shallower sets. Also, to make them look brighter, the power of the electron guns were increased. Not only did this mean that the phosphors would burn out quicker, the preforated metal screen that sits just in front of the screen (shadow mask) to focus the beam on individual phosphor spots had to be altered to take on the higher power. These screens became more prone to warping from the additional heat (the colors would look like they were bleeding out over a wide area instead of being sharply defined).

I too think that the Pioneer Kuro plasmas deliver a terrific picture. As long as one does not require the tremendous brightness of an LCD set (who really does?), good plasmas have less motion artifacts, much more realistic and subtle color, and good black levels. At least Panasonic looks to be carrying on and improving the breed; their newly improved panels look very good).