How Much Overscan Should I Leave (CRT adjustment)?

[Tempest]

I'm currently in the process of fixing the geometry of a 27" CRT that I picked up at MGC (a Samsung TX-S2783). I have it mostly straightened out, although there is a bit of vertical bowing at the top I can't seem to adjust, but now I need to figure out how much overscan I should leave on the sides. Normally I just use the 240p suite on my SNES and keep the entire overscan grid in view, but I've been told that you really don't need to do that and in fact you'll see garbage in that area on some games (not to mention the Genesis is severely underscanned if you do this). So what I've done is make it so my Genesis displays full screen which mean some of the overscan area is off screen. I'm losing half an inch or so on the sides of the screen on my SNES and NES games, but I don't think it's going to hurt anything. Should I extend it more? Some people say to extend the width until the middle of the dots are on the sides (using the 240p grid) which seems a bit excessive to me. Does anyone know if any games (SNES, NES, Genesis, TG-16, etc.) that use the full overscan area for anything?

 

BTW if anyone knows how to adjust this model TV to help eliminate the vertical bowing (the left and right sides of the top of the screen droop a bit, or the middle is bowing outwards) let me know. There's also some blurring on the sides of the screen, but I think this is a known issue for this model of TV.

 

Here's a picture of how it currently looks. I've adjusted it a bit since then but this is pretty close to how it currently looks. The first picture is a bit titled, sorry.

 

 

 

[CatPix]

Overscan is never the same on each system. A good compromise is to use a TV test card; those TV tests card were designed to show the "useful area" of a TV to be tuned by TV shops and by TV manufacturers, so they should offer you a good compromise. Also a color one should help you fine tuning your colors and contrast.

 

This one is a very standard test pattern :

Ideally, the checkerband around it should be barely visible. Given that you have a square corner tube, you might tune your TV so that it's basically invisible, that type of test pattern was designed in an era were TV screens were still slightly rounded all over.

 

This one is one of the best (IMO) for black and white :

https://upload.wikimedia.org/wikipedia/commons/5/5d/Tv.resolution.chart.0249.svg

The only down point is that it was designed in an era where TV screens were more rounded, so the overscan era is very vague, basically "you should be able to see the 4 circles".

[Tempest]

Overscan is never the same on each system. A good compromise is to use a TV test card

 

But how to display that card on my TV? I don't think any of my systems are internet enabled (well maybe the PS2, but I never set that up) and I'd still be confined by that systems overscan issues.

[ChildOfCv]

I'm currently in the process of fixing the geometry of a 27" CRT that I picked up at MGC (a Samsung TX-S2783). I have it mostly straightened out, although there is a bit of vertical bowing at the top I can't seem to adjust, but now I need to figure out how much overscan I should leave on the sides. Normally I just use the 240p suite on my SNES and keep the entire overscan grid in view, but I've been told that you really don't need to do that and in fact you'll see garbage in that area on some games (not to mention the Genesis is severely underscanned if you do this). So what I've done is make it so my Genesis displays full screen which mean some of the overscan area is off screen. I'm losing half an inch or so on the sides of the screen on my SNES and NES games, but I don't think it's going to hurt anything. Should I extend it more? Some people say to extend the width until the middle of the dots are on the sides (using the 240p grid) which seems a bit excessive to me. Does anyone know if any games (SNES, NES, Genesis, TG-16, etc.) that use the full overscan area for anything?

 

BTW if anyone knows how to adjust this model TV to help eliminate the vertical bowing (the left and right sides of the top of the screen droop a bit, or the middle is bowing outwards) let me know. There's also some blurring on the sides of the screen, but I think this is a known issue for this model of TV.

 

Here's a picture of how it currently looks. I've adjusted it a bit since then but this is pretty close to how it currently looks. The first picture is a bit titled, sorry.

 

tv_13.jpg

 

tv_17.jpg

 

tv_18.jpg

For older TVs, the screen warpage was typically fixed with linearity controls. But for a modern TV that likely uses driver ICs and has OSD adjustments, the proper adjustment is probably to clean out the cobwebs.

[CatPix]

 

But how to display that card on my TV? I don't think any of my systems are internet enabled (well maybe the PS2, but I never set that up) and I'd still be confined by that systems overscan issues.

you can burn in on a CD and display it with a DVD player on your TV. Via RF or via composite; note that on most TV, even Rf and composite have different overscans (very visible on older TV where you can see the picture shifting) so you will never have the "perfect" amount of overscan. Not on a regular TV at least.

[Razzie.P]

https://amzn.to/2VXjzyd

 

 

I've been going through the same thing with calibrating a CRT, and that disc was a HUGE help! I found a new copy on ebay for just a few bucks, free shipping. It has step by step setups, plus a plethora of tools for setting geometry/color/overscan/etc.

[youxia]

Personally, I don't even bother that much anymore. I will do some basic adjustments but chasing a "perfect" display on a CRT is a rabbit hole. I used to obsess over it but gave up when I realized that I spend more time tweaking than actually playing games and that I'm never really happy with the results anyway. As it's been said above, some of these factors can differ wildly between platforms. Consoles are one thing but if you then move into microcomputer zone you have to deal with borders and ...bah. Life's too short for that

 

About overscan especially, I just let it go, as long as all the important bits are in view. One advantage of using Raspberry+Retropie or a PC (especially Retroarch) is that you can adjust the display on the fly and also save results (godsend in MAME) so I do that in the more annoying cases.

[Tempest]

True enough, but I'm finding all this adjusting strangely addicting.

 

One odd thing I've noticed is that I'll get the 240p suite grid looking good, but when I try a game like Legend of Zelda: A Link to the Past the menus all look wonky and distorted. I'll fix it so the menus look good but then the grid looks off. I'm more inclined to trust how an actual game looks over that grid, but it's kind of odd.

[youxia]

It kinda makes sense since those games were tested on CRTs back in the day and that grid is a modern invention. I also prefer to use games for quick checks, only use the suite for some basic colour calibration. There are some games which are really good for that, eg Addams Family Values (SNES) because you can scroll in all directions, it has clean, well defined sprites and backgrounds, corner menus and also you don't die instantly. Aerofighters (SNES) for vertical scroll checks. Alex Kidd on Megadrive. 180 from Mastertronic on microcomputers because that big dartboard is good for aspect ratios.

[Tempest]

It kinda makes sense since those games were tested on CRTs back in the day and that grid is a modern invention. I also prefer to use games for quick checks, only use the suite for some basic colour calibration. There are some games which are really good for that, eg Addams Family Values (SNES) because you can scroll in all directions, it has clean, well defined sprites and backgrounds, corner menus and also you don't die instantly. Aerofighters (SNES) for vertical scroll checks. Alex Kidd on Megadrive. 180 from Mastertronic on microcomputers because that big dartboard is good for aspect ratios.

Thanks for the game list, I'll try those and adjust accordingly.

 

I think that grid probably causes more harm than good sometimes.

[CatPix]

That gris is more used to test the screen itself, to check for tearing, misalignment, etc...

It shouldn't be used like a test card, at least not on a CRT.

 

For the menus looking wonky, it's mostly because of the CRT tech. You mgiht notice this with game that show brigh screens (Donkey Kong Country 2 on SNES, with the levels in that dark and the flaslight are really good for that) whe nthe screen goes white, you can hear the TV hgih voltage supply whirring louder and the screen "jumps".

Because you send more energy on the TV screen, and it's a physical thing, you have the canon that moves and the metal grid whit are heated differently, causing distorsion that is purely mechanical.

You can reduce this phenomement by darkenign your screen; it's fascinating to see how things move in place when you reduce brightness.

On older screen, focus is also a dang thing to tune; a bright screen will be blurry, but if you tune the focus on it, then anything not bright white will be blurry as well.

 

Those phenoments are easier to see on TV with manual knows to change this. It's fascinating too to change the brightness from dark to low and see how the picture seems to zoom in and out.

Edited May 8, 2019 by CatPix

[Tempest]

For the menus looking wonky, it's mostly because of the CRT tech. You mgiht notice this with game that show brigh screens (Donkey Kong Country 2 on SNES, with the levels in that dark and the flaslight are really good for that) whe nthe screen goes white, you can hear the TV hgih voltage supply whirring louder and the screen "jumps".

Because you send more energy on the TV screen, and it's a physical thing, you have the canon that moves and the metal grid whit are heated differently, causing distorsion that is purely mechanical.

You can reduce this phenomement by darkenign your screen; it's fascinating to see how things move in place when you reduce brightness.

On older screen, focus is also a dang thing to tune; a bright screen will be blurry, but if you tune the focus on it, then anything not bright white will be blurry as well.

 

Those phenoments are easier to see on TV with manual knows to change this. It's fascinating too to change the brightness from dark to low and see how the picture seems to zoom in and out.

 

Yeah I have a bit of that problem with my SD2SNES menu, when I highlight an item towards the bottom of the list I can see the screen 'bow' a bit on the sides. It's not really an issue though.

[derFunkenstein]

Basically every old system has a line count of 224 (progressive) 448 (interlaced). Right or wrong, I'd push 8 lines off the screen in each direction and then adjust horizontally until you have a 4:3 aspect ratio. Using the 240p test suite as you did ensures that you've got 224 lines, and that's why the top and bottom are perfect.

 

Honestly, it's a personal preference. I think the images you put up look pretty good already. Now you're basically fine-tuning it.

Edited May 9, 2019 by derFunkenstein

[mr_me]

Older systems had 192 active lines and older televisions from the 1970s had more overscan than newer televisions from the 1990s. But I'd go with derfunkenstein's suggestion, unless you have something with more than 224/448 active lines. If you completely eliminate overscan you're making your picture too small unnecessarily.

[Tempest]

My fear is that I'm messing up the aspect ratio by adjusting the vertical and horizontal separately. Should I have the exact same amount of overscan on the vertical and horizontal or should the horizontal have more/less overscan?

[mr_me]

Use a test screen with a circle or square to correct the aspect ratio. Even if you don't do that, it can't be off by too much.

[Tempest]

Use a test screen with a circle or square to correct the aspect ratio. Even if you don't do that, it can't be off by too much.

I have that (linearity test I think it's called), but other than just trying to eyeball it, how do you know if the circle is correct?

[mr_me]

You can measure it with a ruler.

[Tempest]

You can measure it with a ruler.

That... Actually makes sense. I can't believe I didnt think of that.

[Tempest]

This is where I got it tonight. It seems like I can get the grid all nice but when I look some game (like LttP) the menus look skewed (like the box in the upper right). I'm about ready to give up. I really wish I know what was causing the blur on the edges of the screen, sometimes when there's text there it's really noticeable. Maybe I should just stick with my 20" PVM... But 27" is so much nicer...

There is a reset command in the menu. I'm thinking about writing down all the settings and trying that to see if the baseline is better than what I have. I have no idea who did what to this thing before I got it.

[youxia]

This is where I got it tonight. It seems like I can get the grid all nice but when I look some game (like LttP) the menus look skewed (like the box in the upper right). I'm about ready to give up.

 

Well, you've been warned. It is a rabbit hole Especially if you have more than one source.

 

You're right about giving up, just first reset it to defaults, then use the suite to sort the colours and few games to whip the rest into some sort of reasonable shape and then quickly forget about service menus. There is no perfect CRT look, it differes between games and platforms and slight hardware imperfections are the part of the package.

And once you stop fiddling and start actually playing and enjoying the games all these things fade away, because the OCD is in the mind.

 

I have some decent RGB-capable Trinitrons in my other place but for the last several months could only use a no-name composite-fed NTSC set. It's far from perfect but I still prefer it over my modern IPS panel with 1:1 ideal, shader sporting emus.

[Tempest]

What I can't figure out is why the geometry changes between game systems. I'll get all the menus and boarders looking good on LttP on the SNES, but then I'll put in Castlevania 3 for the NES and the text in the upper corner is bowing in (the PLAYER text). I can understand the overscan size being different between systems, but why would the geometry change? I never had this problem on my old CRTs back in the day, sometimes things got cut off and whatnot but the geometry was never wonky (no bending menus and stuff like I'm experiencing here).

[DJ Clae]

The geometry changes with the surrounding brightness on the screen and strength of the signal.

 

It's also possible to have a CRT where the geometry is broken beyond repair in the menus.

[Tempest]

Is it dangerous to reset to default from the service menu? I was going to write down all the values before I did that, but I don't want to make my TV inoperable somehow by doing this.

[CatPix]

What I can't figure out is why the geometry changes between game systems. I'll get all the menus and boarders looking good on LttP on the SNES, but then I'll put in Castlevania 3 for the NES and the text in the upper corner is bowing in (the PLAYER text). I can understand the overscan size being different between systems, but why would the geometry change? I never had this problem on my old CRTs back in the day, sometimes things got cut off and whatnot but the geometry was never wonky (no bending menus and stuff like I'm experiencing here).

Are you sure you simply never noticed?

 

Older CRT with manual controls and no digital processing of the picture unlike yours which is digital would be extremely prone to such things.

The reason you mgiht not have noticed it is that you didn't paid attention that much, or/and that your played via RF, or with a low contrast and/or luminosity, which as we explained, affects how the image is displayer.

Older CRTs up to the late 80's had trouble being clear enough. Ironically, CRT had the opposite issue of LCD : they had too low remanence, which resulted in the picture fading before it could be all displayed.

It's the reason why old B&W and even color CRT tubes up to the 80's are grey and not black : darker phorphors took more energy to make bright, and would then stay lit too long, causing ghosting on the picture quite like you see on older or very cheap LCDs; plus, early ones would burn fast and become grey and white quite fast, resulting in a worn out tube.

Only in the late 80's and 90's "Pitch black" phosphors were used that were stable and good enough to go from complete dark to white and back to black in the required amount of time, and wouldn't wear out in a few years.

So your experience might be that you didn't noticed the slight bowing of the menus back then because unlike what we retrogamers want to think, we had inferior displays compared to the late CRT (my personnal opinion being that with analog picture processing but digital driving of the tube, tube which usually have "dark enough" phosphor, consumers TV from the early 90's are the best for retrogaming)

Edited May 10, 2019 by CatPix