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Thomas Jentzsch

Testing CRT Screen Size

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If you dare, you could open it (high voltage!). There must be some pots around the end of the cathode which might allow adjusting the width.

Already did, that's what I was saying... absolutely none of the pots are responsible for adjusting the width. :mad: :(

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NTSC

Sylvania 32"

 

(Heavy 6'er, RF output)

It was kind of interesting to watch the screen stop rolling then display multiple, stable images, each much shorter vertically than the displayed scan line count as I ran the total scan lines way up above a reasonable number.

Is that an old TV with a rounded screen?

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Is that an old TV with a rounded screen?

Not terribly old. The bezel corners are square. The screen is relatively flat-ish compared to the old 60's/70's stuff.

Edited by BigO

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I have been off of AtariAge for years, and got sucked back in today when I saw that a Atari Flashback Portable is available with SD card. I have a Harmony cart and will see if I can get it setup today/tomorrow. The only CRT TVs I have left are my 9" DVD combo, and my 250 lb Sony WEGA 36" which has not seen power in years.

Do you care which Atari I test with? I pretty much 1 of every, 4sw, 6sw (heavy and light), Jr, 7800...

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My results (NTSC Memorex 9" DVD Combo): (FWIW, it is rock steady even at 257)

  • Cold - NTSC: 28, 215, 19 (but really if you ignore the top left and bottom right corner 27 217 18)
  • Warm - NTSC: 27, 217, 18 (but really if you ignore the top left and bottom right corner 26 218 18)

I think the tube is a smidge clockwise in the cabinet.

Testing on my behemoth 36" WEGA will have to wait a bit, maybe later today or tomorrow.

Edited by Pioneer4x4
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I ran the 1.2

 

My results (NTSC Memorex 9" DVD Combo): (FWIW, it is rock steady even at 257)

  • Cold - NTSC: 27, 216, 19 with seeing Warm - NTSC: 27, 217, 18 (at the 80)
  • The lowest it will go without rolling is 17 204 04
  • The highest is 45 211 40
  • The most lines in the center I could get seems to be 19 220 11 FWIW
  • Warm - NTSC 28 218 18

All were with just ½ a pixel cut off top left and bottom right, so assuming it was straight, maybe 1 less on either end and perfect.

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Well I tested the 36" Sony WEGA and typed it all up, I guess I never posted it. I remember it was 220 in the middle for just about any total count. I can re-test tomorrow. Odd thing was, it would only show in black and white, even the Harmony menu and any ROM I tried.

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TV is a JVC 15'' 4:3 with this results (I was curios and tested it with different machines...)

 

ATARI 2600 4 switch PAL CVBS - 25/215/22

ATARI 7800 PAL Antenna - 25/214/23

ATARI 7800 NTSC Antenna - 25/217/20

ATARI 2600 junior PAL Antenna - 24/216/22

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Thanks for testing. Can you test again with color switch at B&W too?

 

I am surprised that there are any differences at all.

Edited by Thomas Jentzsch

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PAL 24" Panasonic (on for a couple of minutes) It works with PAL60 games.

PAL 6 switch woody

Colour switch set to b&w. Using v1.1

 

29, 265, 18

Edited by davyK
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Tested 1.1 with a Philips 27" PAL TV (warmed up) and a PAL Jr.

 

NTSC: 30, 215, 17
PAL : 34, 264, 24

In PAL mode I can get as high as 299 before the screen starts to roll.

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Thanks for testing. Can you test again with color switch at B&W too?

 

I am surprised that there are any differences at all.

OK here are the results:

 

(No B&W switch on the 7800)

 

ATARI 2600 4 switch PAL CVBS - 33/255/24

ATARI 2600 junior PAL Antenna - 32/257/23

Edited by Tigerduck
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I have updated the results in the first post.

 

Summary: Especially old TVs with rounded corners, can only display 200 (NTSC) respectively 240 (PAL) or less scan lines at full width. If you limit the tested width to 60% (thus excluding the corners), you can use ~10-15 extra scan lines.

 

Conclusion: If you make sure that nothing relevant is displayed in the corners (e.g. display a typical centered score at the top or bottom), you can use 210 (NTSC)/ 250 (PAL) scan lines. And even more, if you ignore certain TVs which have an incorrect, too much zoomed setup (e.g. maybe like Tigerduck's JVC from the post above).

Edited by Thomas Jentzsch
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OK here are the results:

 

ATARI 2600 4 switch PAL CVBS - 33/255/24

ATARI 2600 junior PAL Antenna - 32/257/23

Is that JVC an old TV with rounded corners? If yes, maybe you can repeat your tests with version 1.2

 

If not, then your set up is pretty much off. The picture is too much zoomed vertically.

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Version 1.2 - NTSC - Commodore 1702:

 

16 228 17 = Corners cut fully.

17 226 18 = Corners cut considerably.

18 224 19 = Corners cut nearly unnoticeable.

19 222 20 = Corners fully visible.

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Conclusion: If you make sure that nothing relevant is displayed in the corners (e.g. display a typical centered score at the top or bottom), you can use 210 (NTSC)/ 250 (PAL) scan lines. And even more, if you ignore certain TVs which have an incorrect, too much zoomed setup (e.g. maybe like Tigerduck's JVC from the post above).

 

Thank you for doing this and to everyone who replied. With a display of more than 192 scan lines, what would you recommend doing with the vertical blank and over scan... take half the extra scan lines off of each?

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Thank you for bringing together this testing, Thomas. Reviewing the results, a majority average of 224.1 visible display lines for NTSC is reassuring to see, but not surprising.


The 192 figure is definitely a reference in utilization of much older CRTs from the 60's-70's that had a greater area of the screen cut off from view for the vast majority of displays. This includes harmonizing with the computers from that era, such as the Apple II (280x192) and Atari 400/800 (Max 320x192).


If we take a look at resolutions listed for consoles regarding what was put into practice as reference in the mid 80's/early 90's for the NTSC regions...


NES = 256x224

SMS = 256x224

Genesis = 320x224

SNES = 256x224


...including looking at Stella's younger sister Maria...


Atari 7800 = 160x240/320x240; however, in practice, the max number of lines ever utilized (I.E. Water Ski and Tank Command) is exactly 224...


...the test results make complete sense. :)

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19" Zenith CRT (circa 1997)

 

Atari 2600 Vader NTSC & Atari 7800 (with expansion connector) NTSC using version 1.2 of the screen size software:

 

18 196 12 - smallest stable size (226 total)

32 206 26 - typical size (262 total)

45 210 40 - biggest stable size (295 total)

 

Note: It seems my TV displays too far to the right though, so I do have some cut-off on the right-side corners. I'd approximate its about 4pixels too far to the right. I've tried to compensate with the numbers, so I might be a little bit off.

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NES = 256x224

 

 

Are you sure NES outputs 224 scanlines? I read everywhere that it is 240 actually. Of course not all 240 are used for active playfield - due to those reasons.

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Are you sure NES outputs 224 scanlines? I read everywhere that it is 240 actually. Of course not all 240 are used for active playfield - due to those reasons.

 

Correct. The 224 reference for the NES, as in the case of 7800 Water Ski/Tank Command, is not what it actively puts out - both consoles are 240p, but what is actually utilized (..."put into practice"...) as reference, for how many lines are visible on the screen. Taking into account an average of 8 scanlines cut from the top and 8 scanlines cut from the bottom (240-8-8 = 224), 224 scanlines is the reference for what is seen on the average NTSC (CRT) screen.

 

The results reported for Thomas' test fortifies that fact with the majority of NTSC displays reporting an average of 224.1 visible scanlines.

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Thank you for bringing together this testing, Thomas. Reviewing the results, a majority average of 224.1 visible display lines for NTSC is reassuring to see, but not surprising.

Well, the 224 lines are only visible over 60% of the screen width. If you want to display something important in the corners, you must got down quite a few lines (~200).

 

The 192 figure is definitely a reference in utilization of much older CRTs from the 60's-70's that had a greater area of the screen cut off from view for the vast majority of displays.

I think the 192 is a shortcut for rounded corners. Those old TVs could display more than 200 lines for sure, but not (always) in the corners. So Atari simplified the problem and defined 192 in the programmer's guide.

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