|> > I have heard that only 1/4 of the display on the screen can be recorded into
|> > NTSC (North American) video tape. I thought it should be able to to better
|> > than this.
|> The NTSC standard is 646 x 486 resolution. To record onto video tape,
|> your Personal Iris changes it's video output from the standard 1280
|> So, you are putting the entire screen display to video tape; but the
|> resolution is lower than you are used to looking at.
|> You cannot record a resolution of 1280 x 1024 onto video tape.
|> Your only option if you want to run a program at 1280 x 1024 and
|> record it on NTSC is to run the 1280 x 1024 signal into a scan
|> convertor, which averages it down in size and outputs an NTSC signal.
|> This averaging process will, of course, cause you to lose some detail
|> in your original image.
|> These scan convertor boxes are available from SGI (the VideoCreator),
|> Folsom Research (the Otto), and several other sources.
Unfortunately, it is even far worse than this. Most common video recorders,
such as VHS and SVHS are designed to record Y,I and Q signals (or Y, Cr, and
Cb signals), which are derived from the R,G,and B signals your computer
screen uses. Because of the limited recording bandwidth of the magnetic tape,
bandwidth is allocated between the components, with Y getting about 4MHz, and
the I and Q (or Cr and Cb) getting about 500KHz each. This is a complicated topic,
but the net result is that the horizontal Luminance resolution (Y) is about 320
lines, and the Chrominance resolution (Cr, Cb) is about 40 lines!
If I had to guess at what you are seeing from the tape, it is overall low image
resolution, especially the color resolution, and color noise in the image.
What is truly amazing to me is that video movies still look O.K. with this kind
Why isn't it better than this? Because a VHS VCR needs to sell for around $150.
If you need better quality, it can be had, but you better sell your house to get it.
A D1 tape deck, which stores digital video at full resolution, costs around $100K.