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Thread: Vertical Scan Lines?

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    Insert Coin (Level 0) HyruleHero's Avatar
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    Default Vertical Scan Lines?

    Quick question, I have a couple old CRTs , on most of them I have horizontal scan lines and my retro systems look great, but I have an old 19 Zenith from the 80s and it appeaes to have vertical scan lines and actually the games look even better. Can someone explain this to me? Is there such thing as vertical scan lines? Thanks in advance!

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    Peach (Level 3)
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    I have a 5" Sony PVM that appears to have vertical scanlines. I was told that the small screen wasn't sharp enough to be able to distinguish the usual horizontal scanlines you'd see on a CRT, and the reason it looks like it has vertical scanlines was because of how the phosphors on the aperture grille line up with each other vertically. You can see the effect here and here. There may be something similar going on with yours, even though it's probably either shadow or slot mask and not aperture grill.
    Last edited by jperryss; 07-26-2018 at 03:26 PM.

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    Apple (Level 5) eskobar's Avatar
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    Quote Originally Posted by HyruleHero View Post
    Quick question, I have a couple old CRTs , on most of them I have horizontal scan lines and my retro systems look great, but I have an old 19 Zenith from the 80s and it appeaes to have vertical scan lines and actually the games look even better. Can someone explain this to me? Is there such thing as vertical scan lines? Thanks in advance!
    Scan lines are horizontal because they are a "hack" of the standard set for TV broadcasting. The standard had 480 lines that were painted 60 times a second, the lines were drawn alternating between even and odd lines ... this created flicker and artifacts in the signal.

    Computer and video game manufacturers wanted to draw every line on screen so they cut in half the horizontal lines to 240, and because the technology was not a fixed resolution screen like today, the electron gun simply had a black space between lines. The size of the scanlines depends on the aperture grill and size of the screen, a big monitor with small dot pitch will have very noticeable scan lines, not the case of smaller monitors. Horizontal refresh rate is much higher ...

    It may be an alignment pattern what you see, you should take some shots and share it with us.
    Last edited by eskobar; 07-26-2018 at 06:38 PM.
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    ServBot (Level 11) jb143's Avatar
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    Look up images of 'aperture grille' and 'shadow mask' and you'll see why. Though, unless it's a Sony Trinitron then it likely isn't using an aperture grille, since I don't believe their patent had expired yet. Many shadow masks though try to emulate the effect using vertical bars. The image ends up brighter and more vibrant because more of the phosphor is exposed.

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