[DEmberton]

Quick question:

My UK spec Sony 24" WS TV supports NTSC, which I often use and works fine. Does this mean that when I'm watching NTSC the TV is cleverly upsampling the picture to 576 lines on the fly, or does it change the operation of the gun to only do 480 lines on the screen? What I'm getting at is, if watching in NTSC will it look exactly the same as a US NTSC only TV would?

Dave

[David Robinson]

The TV will display NTSC "as is", with 480 active lines. It would be too complex to convert to 576 lines in a domestic product, because of the problem of dealing with interlace. On my Sony set, and I imagine all widescreen sets, the same applies to zooming out the picture when receiving a letterbox programme. For example a 16:9 letterbox has 432 active lines, and when zooming this out to fill the screen, the set simply overscans the screen so you still have 432 lines. This works fine, the only side effect being a slight drop in brightness since the beam spends more time off screen.

Your NTSC picture will look the same as on an NTSC set.

[DEmberton]

Thanks.

When I use Zoom Mode, I get a horizontal line texture across the image. I always thought this was because it was having to duplicate certain lines, or is it simply because being made bigger 432 lines just doesn't look good? But then surely you'd get the same effect on a larger TV without zoom mode.

I guess what I'm getting at, is is there an actual resolution to the screen, made up of phosphor dots or whatever it is that means you lose quality when using a different resolution?

Dave

[Orbitalzone]

Some (mostly older 4/3 TV's) show NTSC in a slight letterbox format, presumably to keep the image geometry correct.. I guess that technically a PAL tv will slightly stretch the height when on an NTSC signal....so detail may be slightly less than on a true NTSC TV....most TV's these days however seem to just fill the screen like using a zoom function as David said above.

Note that often a Hue control becomes available on the picture settings menu when viewing an NTSC signal, this can correct for odd looking colour errors such as green faces and orangey reds.

[David Robinson]

Quote:

Originally posted by Orbitalzone
Some (mostly older 4/3 TV's) show NTSC in a slight letterbox format...

This I imagine would apply to a set that was not specifically designed for NTSC, but it happens to lock the picture OK. With fewer lines than PAL, and the same line rate (near enough), there would be a loss of height. Modern scan chips are designed to handle both standards and adjust the height automatically.

As for Dave's question about screen resolution, the phosphor stripes on a colour tube are continuous in the vertical direction. You can see this yourself with a magnifying glass. On a Sony Trinitron, the shadow mask is made of vertical wires which have two thin horizontal support wires about a quarter of the way up and down the screen. I can see the shadow of the support wires on my computer VDU as I type. But apart from the support wires, a trinitron can light up the whole phosphor stripe. So there is no structure to interact with the scanning lines.

In the horizontal direction, there can be interaction between the phosphor stripes and the picture detail. Obviously the finer the stripes, the less this will happen. That's why the stripes are much finer on a computer VDU than on a TV.