## zx screen 2

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• ... No. -- ... I didn t understand at first, so I plugged my Spectrum and PS1 into my TV and looked closely at the screen. There are faint black gaps between
Message 1 of 1 , Jan 7, 2011
> So basically the spectrum generates only F1 frames, 50 times a second.

> But what happens with lines that are contained in F2 frames, are those

> updated?

No.

--

> I don't understand, if I only generate F1 frames, I should have

> black lines in F2 frames because those are not updated.

I didn't understand at first, so I plugged my Spectrum and PS1 into my TV and looked closely at the screen. There are faint black gaps between the F1 scan lines, but they're not really noticable.

Then I realised I was thinking "digital" and not "analogue". The TV screen contains a sheet of phosphor with RGB spots arranged into little triangles along a scan line. However, the triangles of odd and even scan lines overlap slightly, so there is a slight blurring between lines 1 and 2, 3 and 4 etc:

----- ----- -----

\R|G/ \R|G/ \R|G/ Line 1

\\B//R\\B//R\\B//

\ /B|G\ /B|G\ /  Line 2

-- ----- ----- --

/ \R|G/ \R|G/ \  Line 3

//R\\B//R\\B//R\\

/B|G\ /B|G\ /B|G\ Line 4

----- ----- -----

Therefore, the effect of not supplying every other scan line does not produce such a noticeable blank line. The downside of the blurring is that it reduces the perceived vertical resolution by about 30%.

An odd line frame is known as Field 1, even line frame as Field 2.

Most LCD televisions on the other hand have a regular and square pixel matrix, where pairs of odd and even scan lines do not overlap:

+-----+-----+-----+-----+

| RGB | RGB | RGB | RGB | ... Line 1

+-----+-----+-----+-----+

| RGB | RGB | RGB | RGB | ... Line 2

+-----+-----+-----+-----+

| RGB | RGB | RGB | RGB | ... Line 3

+-----+-----+-----+-----+

| RGB | RGB | RGB | RGB | ... Line 4

+-----+-----+-----+-----+

In this case, blank lines would be visible. However, I believe that these televisions and displays know when single field frames are being displayed (F1 or F2) and digitally fill-in the missing lines by duplicating the previous line.

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