greg@utcsri.UUCP (Gregory Smith) (02/19/86)
[Yes Virginia, there is a line-eater.] In article <1003@cadovax.UUCP> keithd@cadovax.UUCP (Keith Doyle) writes: >In article <898@h-sc1.UUCP> breuel@h-sc1.UUCP (thomas breuel) writes: >>The way to get good high-resolution displays is not to use high-persistence >>monitors, it is to use higher frequency displays. >Funny, I've gotten used to the advantages of NTSC compatibility and multiple >colors at 640x400x4 [ on Amiga ].... Isn't it the case that 640 dots/line and NTSC compatibilibity represent a contradiction in terms? Consider that 640 pixels/line means about 14M pixels/sec, and that colour is encoded into NTSC at about 3.5MHz, meaning that each cycle of the subcarrier spans 4 pixels, thus it is effectively impossible to set any individual pixel to any colour you want and have it show up that way. ( Take a good look at the workings of an Apple ][ display for further insight into this. It is really just a B&W graphics display with a chroma burst so your TV thinks it's colour. Ingenious for its time, but colour combinations are limited). Note to people turning on their flame-throwers: Yes, the above problem does not apply when an RGB monitor is used, only when the signal is somehow encoded into NTSC before being displayed. However, NTSC compatibility means that one is limited to 15.75Khz horizontal frequency, about 450 lines max, and 30Hz frame refresh. Increasing vertical resolution is thus impossible, and significant increases (1000 pixels ) in horiz. res. require very fast logic and lots of time is wasted in blanking. Except where colour is *really* needed, I would much rather have a good sharp B&W display than a mediocre colour one. My Epson QX-10 has a 640x400 non-interlaced Black&Green display with 45Hz[really] refresh, and individual pixels in a line can be seen ( only if you want to and look closely). The above quoted article also talked about phosphor persistance. The Epson has a medium-persistance phosphor, which can be annoying at times, but not as annoying as flicker. Incidentally, I have heard tell of a coming Colour TV standard with about 1000 lines and a higher subcarrier frequency, which will help eliminate the problems mentioned. Until then, broadcast video standards are for watching broadcast video! bring on RGB. :-) :-) Greg Smith U of Toronto