NES vs. SNES screen resolution

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JimDaBim
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NES vs. SNES screen resolution

Post by JimDaBim » Wed Jun 05, 2013 5:37 am

I've got a question about the resolution of the NES vs. the resolution of the Super Nintendo:

The NES is 256 x 240 while a standard NTSC TV typically just shows 256 x 224 of the pixels. But from a pure data point of view, it's 256 x 240 and you can make the additional rows visible in an emulator.
The Super Nintendo is 256 x 224 and even in an emulator, you see just that, not 256 x 240.

So, does that mean that the Super Nintendo has a lower resolution than the NES?

And if a TV cuts off some of the rows from the NES image, wouldn't that mean that the TV cuts off rows from the Super Nintendo image as well? And since the Super Nintendo has only 224 pixel rows natively, wouldn't that mean that the Super Nintendo image as shown by an NTSC TV screen is even less than 224 rows while the same TV screen does show 224 line of the NES's 240 lines?

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Bregalad
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Re: NES vs. SNES screen resolution

Post by Bregalad » Wed Jun 05, 2013 6:06 am

The SNES have one bit somewhere that allows you to automatically remove the overscan area, and not all games use this option. Therefore games can be 256x224, 256x240, or even something else if hires or interlaced mode are considered.

And if a TV cuts off some of the rows from the NES image, wouldn't that mean that the TV cuts off rows from the Super Nintendo image as well?
Absolutely.

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Re: NES vs. SNES screen resolution

Post by thefox » Wed Jun 05, 2013 6:10 am

Bregalad wrote:
And if a TV cuts off some of the rows from the NES image, wouldn't that mean that the TV cuts off rows from the Super Nintendo image as well?
Absolutely.
Sure, but it doesn't mean that if, for example, the TV cuts 16 scanlines from top and bottom of the NES' 240 scanlines, that it would cut 16 scanlines from top and bottom of SNES' 224 scanlines as well.
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natt
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Re: NES vs. SNES screen resolution

Post by natt » Wed Jun 05, 2013 7:24 am

JimDaBim wrote: And if a TV cuts off some of the rows from the NES image, wouldn't that mean that the TV cuts off rows from the Super Nintendo image as well? And since the Super Nintendo has only 224 pixel rows natively, wouldn't that mean that the Super Nintendo image as shown by an NTSC TV screen is even less than 224 rows while the same TV screen does show 224 line of the NES's 240 lines?
No, because the image that a SNES sends to the TV includes all of those extra lines -- they're just empty black, and can't be used to display graphics.

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koitsu
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Re: NES vs. SNES screen resolution

Post by koitsu » Wed Jun 05, 2013 7:46 am

The register Bregalad is referring to is bit 2 of SETINI ($2133), where 0 = 224 vertical lines, 1 = 239 vertical lines, barring use of interlace mode (which is its own beast in itself).

No where in any of the developers manual documentations that I have does Nintendo state you should avoid using certain ranges of columns (vertical) or lines (horizontals) of pixels to deal with visual areas which may be hidden by the physical border of certain television sets. This information is considered one of those "tribal knowledge" things when working with either NTSC or PAL.

Furthermore, the SNES/SFC offers a high-resolution interlaced mode (controlled via bit 0 of INISET). The way this works depends on what video mode you're using; video modes 0-4 and 7 behave differently than modes 5 and 6 when using interlaced mode. There's too much to discuss about this mode in a post, so I'm not going to (if you want to read more about it, drop me a PM and I can give you a link to a PDF that you can enjoy sifting through). There are games which use this, usually as a "high resolution" title screen with little to no animation (example title: Yuu Yuu Hakusho Tokubetsu Hen's first couple screens when powering on the system).

Finally, there is what's called "H-Pseudo 512" mode (controlled via bit 3 of INISET), where in modes 0-4 and 7 you get visually 512 horizontal pixels of resolution, with the console itself doing a form of blending/averaging between two pixels (i.e. if normally two pixels of red (rgb 255,0,0) and black (rgb 0,0,0)) were next to one another, this mode would result visually in 3 pixels: rgb 255,0,0 / rgb 128,0,0 / rgb 0,0,0. You cannot use add/sub screen capabilities when using H-Pseudo 512. I've never seen this used, but there are probably some games that I've never played which do.

So no, the SNES/SFC does have generally higher resolution modes than the NES, but they are not commonly/consistently used throughout lots of games. They're less common given their limitations and higher complexities. Most people use 256x240 or 256x224. NTSC vs. PAL plays a role here, obviously.

Bottom line: games on the SNES/SFC tended to use all the available pixels, and DO NOT avoid use of certain areas (columns or lines) just because "someone's TV might cut it off". If someone's TV cut off some of the visual area, the owner/user was expected to adjust the H-size or V-size of their TV. Meaning: there was less concern over the "title safe" and "action safe" areas (see wikipedia for what those terms mean), and people were simply expected to adjust their TV sets.

For example on my Sony Trinitron CRT/TV, with many NES and SNES games I have difficulty seeing the top and bottom 4-5 scanlines given how the actual TV operates/behaves. The solution is for me to adjust (decrease) V-size slightly.

The thing the NES did with PPUMASK ($2011) bits 1 an 2 (show/hide the left 8 most pixels of the screen for BG and sprites, respectively) was just silly. There is nothing like that on the SNES/SFC.

P.S. -- 256x240 mode does not "show extra black" at the bottom of the screen compared to 256x224. Instead, what ends up happening is that in 256x224 VBlank lasts a bit longer (meaning with NTSC you have less VBlank time). The same applies on the NES.

P.P.S. -- I'll drop byuu a PM on here and let him know of this thread (since it's in the NESdev section not SNESdev, not sure if he visits the non-SNES sections), as he can probably add some clarification to some of what I've said.

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Re: NES vs. SNES screen resolution

Post by tepples » Wed Jun 05, 2013 8:26 am

koitsu wrote:No where in any of the developers manual documentations that I have does Nintendo state you should avoid using certain ranges of columns (vertical) or lines (horizontals) of pixels to deal with visual areas which may be hidden by the physical border of certain television sets.
But it's in the background planning sheets used by Nintendo during the development of Super Mario Bros. and The Legend of Zelda, which assume a title safe area of (16, 24) to (223, 215), missing 24 lines at top and bottom and 16 pixels on each side of the line.

After studying several TV sets, I'd assume a safe area that happens to be identical to the area displayed by PocketNES: (8, 16) to (223, 229), missing 16 on top, 11 on bottom, and 8 on each side. The imbalance between top and bottom appears to come from how analog TVs' vertical retrace circuits handle the slightly faster frame rate of the NES and Super NES. For the Super NES, I'd preliminarily guess 8 on top and 5 on the bottom. Digital TVs tend to be more even with what they cut off.
Finally, there is what's called "H-Pseudo 512" mode (controlled via bit 3 of INISET), where in modes 0-4 and 7 you get visually 512 horizontal pixels of resolution, with the console itself doing a form of blending/averaging between two pixels [...] I've never seen this used, but there are probably some games that I've never played which do.
Jurassic Park and Kirby's Dream Land 3 apparently use this to enable certain blending effects that involve background + foreground + solid color.
If someone's TV cut off some of the visual area, the owner/user was expected to adjust the H-size or V-size of their TV.
I thought only composite computer monitors, not TVs, had those knobs accessible to the user. But I do remember seeing a caution in the manual for Jeopardy! 25th Anniversary Edition about how older sets with rounded corners might cut off information.
Meaning: there was less concern over the "title safe" and "action safe" areas (see wikipedia for what those terms mean), and people were simply expected to adjust their TV sets.
NESdev Wiki has its own article about overscan and pixel aspect ratio, including test results from actual TVs.
The thing the NES did with PPUMASK ($2011) bits 1 an 2 (show/hide the left 8 most pixels of the screen for BG and sprites, respectively) was just silly. There is nothing like that on the SNES/SFC.
Other than the window register set, which is essentially a more general version of the same clipping functionality that's often manipulated with HDMA. Kirby Super Star uses it for the same reason as NES games: to hide artifacts of horizontal or 1-screen mirroring. F-Zero uses it for the player's shadow, and Super Mario Kart uses it for the player's position.

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Re: NES vs. SNES screen resolution

Post by natt » Wed Jun 05, 2013 8:44 am

koitsu wrote: P.S. -- 256x240 mode does not "show extra black" at the bottom of the screen compared to 256x224. Instead, what ends up happening is that in 256x224 VBlank lasts a bit longer (meaning with NTSC you have less VBlank time). The same applies on the NES.
I assume you meant to to say:
256x224 mode does not "show extra black" at the bottom
From the point of view of the TV, it does; 256x224 mode is just 256x240 mode with extra black lines at top and bottom. Yes, from the point of view of the console, you get extra vblank time, but I was talking about how things get presented on the TV.

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Re: NES vs. SNES screen resolution

Post by blargg » Wed Jun 05, 2013 11:04 am

tepples wrote:
If someone's TV cut off some of the visual area, the owner/user was expected to adjust the H-size or V-size of their TV.
I thought only composite computer monitors, not TVs, had those knobs accessible to the user.
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Re: NES vs. SNES screen resolution

Post by tepples » Wed Jun 05, 2013 11:16 am

TVs didn't always come with instructions to access the service menu, and Google didn't exist until the Super NES era was pretty much over.

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Re: NES vs. SNES screen resolution

Post by natt » Wed Jun 05, 2013 11:36 am

I had at least one old beater TV (late 70s, early 80s) with manual knobs on the back for image adjustment. you could get the entire NES 240 high to show up as visible on it (but not the whole 256 wide, iirc; h-size knob covered much less ground than the v-size knob).

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Re: NES vs. SNES screen resolution

Post by mikejmoffitt » Wed Jun 05, 2013 11:52 am

koitsu wrote:Finally, there is what's called "H-Pseudo 512" mode (controlled via bit 3 of INISET), where in modes 0-4 and 7 you get visually 512 horizontal pixels of resolution, with the console itself doing a form of blending/averaging between two pixels (i.e. if normally two pixels of red (rgb 255,0,0) and black (rgb 0,0,0)) were next to one another, this mode would result visually in 3 pixels: rgb 255,0,0 / rgb 128,0,0 / rgb 0,0,0. You cannot use add/sub screen capabilities when using H-Pseudo 512. I've never seen this used, but there are probably some games that I've never played which do.
Is this the mode that Kirby's Dreamland 3 uses for transparency effects? I bring this up because on my LCD monitor that takes S-video, the 512 columns can be very clearly differentiated and do not blend the way they would be expected to.

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Re: NES vs. SNES screen resolution

Post by lidnariq » Wed Jun 05, 2013 3:52 pm

mikejmoffitt wrote:Is this the mode that Kirby's Dreamland 3 uses for transparency effects? I bring this up because on my LCD monitor that takes S-video, the 512 columns can be very clearly differentiated and do not blend the way they would be expected to.
Using composite, Svideo, or component? They really ought to blur completely using composite, and the hue (but not brightness) should blur using s-video...

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Re: NES vs. SNES screen resolution

Post by BMF54123 » Wed Jun 05, 2013 4:04 pm

The columns are not blended by the SNES hardware itself, but rather by the display device. Using one with sufficient resolution (like an LCD) will indeed show each one individually.

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Re: NES vs. SNES screen resolution

Post by koitsu » Wed Jun 05, 2013 5:12 pm

mikejmoffitt wrote:
koitsu wrote:Finally, there is what's called "H-Pseudo 512" mode (controlled via bit 3 of INISET), where in modes 0-4 and 7 you get visually 512 horizontal pixels of resolution, with the console itself doing a form of blending/averaging between two pixels (i.e. if normally two pixels of red (rgb 255,0,0) and black (rgb 0,0,0)) were next to one another, this mode would result visually in 3 pixels: rgb 255,0,0 / rgb 128,0,0 / rgb 0,0,0. You cannot use add/sub screen capabilities when using H-Pseudo 512. I've never seen this used, but there are probably some games that I've never played which do.
Is this the mode that Kirby's Dreamland 3 uses for transparency effects? I bring this up because on my LCD monitor that takes S-video, the 512 columns can be very clearly differentiated and do not blend the way they would be expected to.
Show me a video (Youtube, etc.) of said transparency effects and I can probably tell you. The most common "transparency" used on the SNES is the screen add/sub stuff, which is separate/independent of H-Pseudo 512.

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Re: NES vs. SNES screen resolution

Post by koitsu » Wed Jun 05, 2013 5:15 pm

BMF54123 wrote:The columns are not blended by the SNES hardware itself, but rather by the display device. Using one with sufficient resolution (like an LCD) will indeed show each one individually.
Thanks for the clarification -- actual displays (meaning the technology, aside from the obvious electron gun behaviour + HBlank + VBlank) and how they work is something I do not understand. I always appreciate the insights.

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