Atari 2600 Display Issues

[atarifan]

On the Atari 2600, does anyone know what the explanation is
for the horizontal black lines that break up the left margin of the game
screen on some games? Sometimes the game picture can be offset half way
through the screen also or there can be a blue vertical line on the left
margin for games with a black background.

What gives?

atarifan

[Leo Ames]

The short black lines that are on the left side of the screen in some games are motion blanking lines that follow objects on screen. When the Atari 2600 draws an object on the screen, it must first be positioned. Because of the console's modest design, the TV has already begun drawing the line before the console has finished shifting the object into place. So there is a small amount of black sent to the TV during the time the console is still busy moving the object.

 

As for the blue on the far left of the screen, its a way to hide these lines. As for the screen offset thing you mentioned, I don't have a clue and don't recall ever seeing it, what games does it happen during? Its likely another way to hide the motion blanking lines.

[Adamant1]

Check out Circus Atari for a brilliant olution o the problem. In that game, the blck lines were turned into a small platform for one of the clowns to jump from.

[Alienblue]

An early name for those lines was "choose set"; what L.A. said is pretty much right on, but as an artist I can give you an analagous explanation: pretend the 2600 needs a series of "magic wands" to hang sprites from. the wands themselves are invisable but the handles cannot be made invisable! That's why you see these lines move up n' down, on some games.

As graphics got better Atari kept trying to come up with ways to hide the CS lines. Galaxian is a good example. The coin-op has no border but the 2600 does-to hide the lines! Lots of games just stuck a colored bar of different sizes over it. The easiest idea was just to make the bars the same color as the background. Normally you don't see them in ATLANTIS by Imagic, i.e., but watch for them when a flash bomb explodes!

[chrisbid1]

activision solved the problem by pushing the entire playfield to the left. the lines were still there, but outside the viewing area of the tv.

[atarifan]

See attached pics of Moon Patrol for example of "off-set" vertical blue line on left margin of screen.  Does this same thihg on some other games too.  Any ideas?

 

[QUOTE=Leo Ames]

The short black lines that are on the left side of the screen in some games are motion blanking lines that follow objects on screen. When the Atari 2600 draws an object on the screen, it must first be positioned. Because of the console's modest design, the TV has already begun drawing the line before the console has finished shifting the object into place. So there is a small amount of black sent to the TV during the time the console is still busy moving the object.

 

As for the blue on the far left of the screen, its a way to hide these lines. As for the screen offset thing you mentioned, I don't have a clue and don't recall ever seeing it, what games does it happen during? Its likely another way to hide the motion blanking lines.

[/QUOTE]

[Leo Ames]

I'm curious to see if it happens to me then. Don't have the 2600 cart and just mailed my 7800 out today for some work to be done to it, when I get it back i'll fire up Moon Patrol on the Cuttle Cart II and see if it does it for me.