toshi@cunixf.cc.columbia.edu (Toshi Kawanishi) (03/28/91)
Does anyone know what happens to the image on the screen when the resolution of the monitor is smaller than the resolution required by the video signal? I'm planning to buy a Next Color slab and I was hoping to connect my multisync instead of dishing out over $2,100 for a 16" monitor from Next !-(that's with Educational discount!) It's a Sony, but still... I found out from Next that the slab requires a monitor with: - 68Hz refresh - 1120 x 832 resolution - 3 BNC inputs (I guess Sync is on the Green) <They claim that it should work, but weren't too enthusiastic about it.> My multisync has enough bandwidth to handle the timing, but falls short on the resolution. My sparse understanding of this subject leads me to believe that I will just lose some pixels. However, my worry is that the beam will stay at the right most pixels and the last line waiting for the sync signals during those missing pixels. If this is true, can it damage my monitor? Or do I worry too much? I could live without some pixels for a while. /toshi (toshi@cunixf.cc.columbia.edu)
naegle@icon.asd.sgi.com (David Naegle) (04/10/91)
In article <1991Mar28.072150.5375@cunixf.cc.columbia.edu>, toshi@cunixf.cc.columbia.edu (Toshi Kawanishi) writes: >Does anyone know what happens to the image on the screen when >the resolution of the monitor is smaller than the resolution >required by the video signal? >I found out from Next that the slab requires a monitor with: > - 68Hz refresh > - 1120 x 832 resolution > - 3 BNC inputs (I guess Sync is on the Green) >My multisync has enough bandwidth to handle the timing, but falls >short on the resolution. My sparse understanding of this subject >leads me to believe that I will just lose some pixels. However, my >worry is that the beam will stay at the right most pixels and the last >line waiting for the sync signals during those missing pixels. >If this is true, can it damage my monitor? Or do I worry too much? It won't damage your monitor and you won't 'lose' any pixels. The worst that will happen is that the color shadow mask will not 'sample' the pixels well enough for you to distinguish fine features in the image. Text may not look as good as you'd expect. The problem is *not* that you won't have *some* of the pixels; *all* of the pixels will either have problems, or appear to be fine. Ideally, the color shadow mask should be small enough to sample a pixel raster such that the Nyquist criterion is satisfied, i.e., at twice the pixel resolution or greater. In practice, this is almost never the case. Effects like moire patterns commonly result from the shadow mask under-sampling the raster. The actual results depend on a number of other factors as well, such as the beam size and shape, the color shadow mask pitch, hole size and hole pattern, beam focus, etc. The only way to know for sure is to try it, preferably before you buy. >/toshi (toshi@cunixf.cc.columbia.edu) -- naegle@sgi.com (David Naegle) {sun|decwrl|pyramid|ucbvax}!sgi!naegle The difference between theory and practice is always greater in practice than in theory. disclaimer: The opinions above are strictly my own.
izumi@mindseye.berkeley.edu (Izumi Ohzawa) (04/10/91)
In article <1991Apr10.022848.14504@odin.corp.sgi.com> naegle@icon.asd.sgi.com (David Naegle) writes: >In article <1991Mar28.072150.5375@cunixf.cc.columbia.edu>, >toshi@cunixf.cc.columbia.edu (Toshi Kawanishi) writes: > >>Does anyone know what happens to the image on the screen when >>the resolution of the monitor is smaller than the resolution >>required by the video signal? > >>I found out from Next that the slab requires a monitor with: >> - 68Hz refresh >> - 1120 x 832 resolution >> - 3 BNC inputs (I guess Sync is on the Green) You are missing a critical spec which is that the monitor can sync to 63-64kHz Horizontal scan rates. Although not many ads for monitors have that info, that's the most critical info needed for choosing monitors. Usually, you have to get more technical spec, or users/oweners manual to get that number. > >>My multisync has enough bandwidth to handle the timing, but falls >>short on the resolution. My sparse understanding of this subject >>leads me to believe that I will just lose some pixels. However, my I am not sure if your monitor does. Go get the manual for the monitor, and check the range for H-scan rate to which the monitor is able to lock onto. Many muti-syncs, such as NEC 3D, 4D's can't do it. Neither does Seiko's CM-1440. I.E., most monitors sold for super-VGA for PC's can't be used. (For example, CM-1440 can lock to 31-40kHz H-scan rate.) So, look for ads, call manufactures and ask if the monitor you are interested in can handle 64kHz H scan rate. Pixel resolutions such as 1024x768, 1120x832 don't mean much. Ask for someone who knows what "horizontal scan frequency" means. Phospher triad pitch, as David says, is important once you can obtain sync, but many multi-sync monitors won't just sync to the video signal. And if you don't get sync, you get no picture. >>If this is true, can it damage my monitor? Or do I worry too much? And I believe that driving monitors with wrong scan rates for an extended period of time WILL damage monitors. It can even be a fire hazard. Remember orginal IBM PC monochrome monitor which had exactly this problem. You are taking a chance if you believe that newer monitors are protected from the overload resulting from out-of-range scan rates. Izumi Ohzawa [ $@Bg_78^=;(J ] USMail: University of California, 360 Minor Hall, Berkeley, CA 94720 Telephone: (415) 642-6440 Fax: (415) 642-3323 Internet: izumi@violet.berkeley.edu NeXTmail: izumi@pinoko.berkeley.edu