1080p vs. 1080i on Plasma/LCD?
jwbeck17 -- Sat, 07/22/2006 - 08:50
I'm interested in getting your feedback on this. I can understand the visual difference of 1080p versus 1080i on a CRT or DLP screen, however is there a difference between i and p on a plasma or LCD screen? Don't both plasma and LCD automatically provide progressive images due to their technology?
Actually, DLP is in the same category as plasma and LCD in this regard (and LCoS, too, for that matter): All pixel-based displays ultimately require a progressive signal to display the image. Only CRTs can display in interlaced image without converting it to progressive first. And you are correct that displaying an interlaced image on a CRT is generally not as good as displaying a progressive image.
The difference in quality you might see comparing one pixel-based display or technology to another depends to some extent on how well the deinterlacing process is performed; this is the job of the display's video processor, and some do it much better than others. Alternatively, the source device or an outboard video processor can do the job; the trick is to determine which one does it best.
Another common misconception about pixel-based displays is that they are inherently progressive. It's true that they require a progressive signal, but they do not display the image in a progressive or interlaced manner--that is, they do not draw horizontal picture lines one at a time like a CRT. Instead, they flash each entire frame all at once. The only exception I can think of is the Hitachi plasma panels that use a technology called ALiS (Alternate Lighting of Surfaces), in which vertically adjacent rows of pixels share the same electrode, which drives them alternately, somewhat like interlacing.
Scott Wilkinson
Video Editor
The Perfect Vision
Post new comment