keithe%tekgvs%tektronix.csnet@csnet-relay.arpa (09/12/85)
From: keithe%tekgvs%tektronix.csnet@csnet-relay.arpa Subject: Interlaced monitor Date: 10 Sep 85 17:03:33 GMT Apparently-To: info-amiga-from-usenet@RUTGERS >> I can't figure out what an interlaced monitor is. >> What will look better in the Amiga: 640x400, or >> 640x200? Does it matter? >The price one pays is flicker, since screen sweeps are only done 30 >times a second, as opposed to 60 times a second during non-interlace. >Thus a higher persistance monitor is needed to eliminate flicker. Well, not really... One of the *advantages* of interlace is that flicker is reduced. A "half" frame is generated every 1/60 of a second, but that half-frame is distributed over the entire face of the crt. Then, 1/60th of a second later, the intervening lines are drawn for the other half of the frame. (P.S., each half-frame is referred to as a "field.") So the eye thinks it's getting refreshed 60 times every second - because it can't distinguish the separate lines - instead of at a 30 per second, which would be very noticeably flickering. Keith Ericson at TekLabs (resident factious factotum) Tektronix, PO 500, MS 58-383 Beaverton OR 97077 (503)627-6042 uucp: [ucbvax|decvax|ihnp4|(and_many_others)]!tektronix!tekgvs!keithe CSnet: keithe@tek ARPAnet: keithe.tek@rand-relay
skinner@saber.UUCP (Robert Skinner) (09/13/85)
> From: keithe%tekgvs%tektronix.csnet@csnet-relay.arpa > > > >> I can't figure out what an interlaced monitor is. > >> What will look better in the Amiga: 640x400, or > >> 640x200? Does it matter? > > >The price one pays is flicker, since screen sweeps are only done 30 > >times a second, as opposed to 60 times a second during non-interlace. > >Thus a higher persistance monitor is needed to eliminate flicker. > > Well, not really... One of the *advantages* of interlace is that > flicker is reduced. A "half" frame is generated every 1/60 of a second, > but that half-frame is distributed over the entire face of the crt. > Then, 1/60th of a second later, the intervening lines are drawn for the > other half of the frame. (P.S., each half-frame is referred to as a > "field.") So the eye thinks it's getting refreshed 60 times every > second - because it can't distinguish the separate lines - instead of > at a 30 per second, which would be very noticeably flickering. > > Keith Ericson at TekLabs (resident factious factotum) > Tektronix, PO 500, MS 58-383 > Beaverton OR 97077 > (503)627-6042 > uucp: [ucbvax|decvax|ihnp4|(and_many_others)]!tektronix!tekgvs!keithe > CSnet: keithe@tek > ARPAnet: keithe.tek@rand-relay NO, NO, NO!! If you draw a lone horizontal line on the screen, it *will* flicker, because it is only refreshed 30 times a second. Even if you are thinking about large painted areas it doen't work. The two fields are (ideally) displaced by the size of a scan-line (Or you don't actually get the required resolution). This usually results in a lower overall intensity, unless you have very long persistence phosphor. But very long persistence phosphor "streaks" when you try to do dynamic frames, i.e. real-time graphics. You're not in the monitor or graphics design groups are you? Non-interlaced Forever... ------------------------------------------------------------------------------ .. man then went on to prove that black was white, and was promptly killed at the next zebra crossing. Name: Robert Skinner Snail: Saber Technology, 2381 Bering Drive, San Jose, California 95131 AT&T: (408) 945-0518, or 945-9600 (mesg. only) UUCP: ...{decvax,ucbvax}!decwrl!saber!skinner ...{amd,ihnp4,ittvax}!saber!skinner
neal@weitek.UUCP (Neal Bedard) (09/17/85)
In article <3629@topaz.RUTGERS.EDU>, keithe%tekgvs%tektronix.csnet@csnet-relay.arpa writes: > From: keithe%tekgvs%tektronix.csnet@csnet-relay.arpa > >> I can't figure out what an interlaced monitor is. > >> What will look better in the Amiga: 640x400, or > >> 640x200? Does it matter? > > >The price one pays is flicker, since screen sweeps are only done 30 > >times a second, as opposed to 60 times a second during non-interlace. > >Thus a higher persistance monitor is needed to eliminate flicker. > > Well, not really... One of the *advantages* of interlace is that > flicker is reduced. A "half" frame is generated every 1/60 of a second, > but that half-frame is distributed over the entire face of the crt. > Then, 1/60th of a second later, the intervening lines are drawn for the > other half of the frame. (P.S., each half-frame is referred to as a > "field.") Er, not exactly. The rationale for using interlace is to increase the spatial resolution of the screen *without* increasing video bandwith. Interlace would be fine, except that long-persistence monitors tend to be not as bright, and the `flicker' is *still* noticeable on long, bright horizontal lines - headache fodder for the operator. Also, lp monitors tend to leave afterimages, annoying if stuff is happening in realtime on the screen. Most medium-to-high end 1280 x 1024 terminals nowadays use 60hz non-interlaced scanning with high-bandwidth (120+ MHz) monitors - including the Tek 4115/4129 series (don't forget to ask about the F59 solids modelling option ... :-)) Some manufacturers opt for a slightly higher scan rate - 33hz int/66hz non - (33hz field-rate) to eliminate all vestiges of flicker noticeable on even the best 30/60hz terminals. You have to be really picky to tell the difference, and the difference is dependent on the viewing brightness and ambient light level. Just wanted to set the record straight, Time to go back to net.graphics :-) -Neal -- "whaddya mean there were bullet-holes in his mirror..." UUCP: {turtlevax, resonex, cae780}!weitek!neal
caf@omen.UUCP (Chuck Forsberg WA7KGX) (09/22/85)
My eyes see flicker on many CRT's when they are used in rooms illuminated by flourescents. In a room with regular light bulbs and/or ambient sunlight, a P4 phosphor is just fine at normal brightness, even with interlaced video! This combination gives *me* less flicker than some of the smeary pastey long persistience green phosphors viewed under flourescents. So, if you're bothered by CRT flicker, try turning off the flourescents. No guarantees, of course. -- Chuck Forsberg WA7KGX ...!tektronix!reed!omen!caf CIS:70715,131 Omen Technology Inc 17505-V NW Sauvie Island Road Portland OR 97231 Home of Professional-YAM, the most powerful COMM program for the IBM PC Voice: 503-621-3406 Modem: 503-621-3746 (Hit CR's for speed detect) omen Any ACU 1200 1-503-621-3746 se:--se: link ord: Giznoid in:--in: uucp