From: iisakkil@lesti.hut.fi (Mika Iisakkila) Subject: Re: Mis-convergence vs mis-registration (Was:What the 17" monitor reviews) Date: 2 Aug 1992 15:22:37
wlsmith@valve.heart.rri.uwo.ca (Wayne Smith) writes:
>I think he means mis-registration.
They are essentially the same thing. Both terms come from the video
world, and refer to the same problem: how to get the images produced
by the red, green and blue electron guns to overlap properly.
"Convergence" is used when discussing colour monitors and
"registration" with three-tube colour cameras.
>Pure colors look fine, but some dithered colors show a kind of herring bone
>effect.
This is another problem, called "Moire patterns". In TV jargon, they
refer to coloured patterns produced by electrical interference or the
striped shirt of your favourite news anchor.
Computer screens typically have much higher resolution, and offer
another source for Moire interference patterns. If the pixel size of
the graphics mode you're using is close to the dot size of your
monitor, you may see interference in dithered colours. Take for
example dithered 50% gray (every other pixel white, every other
black). In some area, it may happen that all the white pixels land
only on the red phosphor dots in your monitor, and you see only red!
Of course, you'd have to be extremely "lucky" to have this happening
on any large area, so you're more likely to see the "rainbow" effect.
This is not a specific problem with big monitors, you can find
offending pixel/dot resolution combinations in all monitors. I've seen
this on my 14" screen.