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PostPosted: Sun Jun 25, 2017 12:53 pm 
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Today, I tried out the NTSC Super Nintendo that I bought from eBay.
And I noticed that the colors are much too saturated relative to the NES.

When I got my CRT TV, I calibrated it so that NES games look good on it.
But when I connect the Super Nintendo to the same TV with the same configuration, the colors are too powerful, especially the red ones.

For example, when I play Powerman's stage in "Mega Man I" on the NES, the red background looks normal.
But when I play "Street Fighter II - The World Warrior" on the SNES, then the "Street Fighter II" logo, Ryu's red stage and the empty health bar are basically illuminating.

I know it's not the same red color between the NES and the SNES. But that's beside the point.
I can make the NES red illuminate just as well if I simply increase color saturation.
And if I decrease color saturation, so that the SNES looks fine, then the NES looks too pale.

Is this a known issue?
Do I really have to change the color values according to the current console everytime I play?

Or does this have to do with the cable?
For the NES, I use a standard yellow and white composite AV cable.
For the SNES, I use the one where you put the gray plug into the SNES and the yellow, white and red composite AV cable goes into the TV.

For the SNES, I'm using an authentic cable by Nintendo. The SNES came with some third party replacement cable that didn't work at all, so I couldn't compare it. (But I had bought the Nintendo one separately anyway.)
I bought my Nintendo cable in Germany since I assume they are all the same. Or are there known differences between the American and the European one or between the one used for the SNES and the one used for the N64?

By the way, my SNES PCB revision is SNS-CPU-GPM-02. (I opened it to check this.)

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PostPosted: Sun Jun 25, 2017 2:28 pm 
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Doesn't the NES's red produce out-of-spec values, whereas the SNES doesn't? I wonder if that's behind it treating the two consoles way differently, though I wouldn't know what to do about it.


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PostPosted: Sun Jun 25, 2017 4:56 pm 
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NovaSquirrel wrote:
Doesn't the NES's red produce out-of-spec values, whereas the SNES doesn't?

I don't know. Does it?

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PostPosted: Sun Jun 25, 2017 6:44 pm 
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NES colors only have an amplitude of +/- 33 IRE, where as NTSC's red has an amplitude of +/- 63 IRE, so it makes sense that certain colors look dull on the NES.


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PostPosted: Mon Jun 26, 2017 1:00 am 
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That's a bit too technical for me.

What I'd like to know is: Have other people experienced this?

If you calibrate your TV, so that the colors look alright and similar to the palettes that emulators use, did you notice that the colors on the Super Nintendo are much too powerful?

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PostPosted: Mon Jun 26, 2017 11:58 am 
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Yes, the SNES outputs more saturated reds than the NES. Explaining the reason for this requires becoming very technical.

Your CRT TV assumes that NTSC-encoded signals use NTSC colorimetry. That means to display it correctly even though it uses modern colorimetry, it will apply a correction matrix to the RGB signals gained from decoding the NTSC signal, which in practice boosts the red channel. As the NES does not process RGB internally, but directly generates an NTSC signal, this is appropriate.

The SNES on the other hand internally process RGB directly, and SNES graphics artists chose RGB values based on modern colorimetry as seen on their development system monitors. Your TV doesn't know this, and therefore assumes NTSC rather than modern colorimetry, and boosts red when it shouldn't.

The solution should be to avoid the NTSC encoding-decoding process by getting the SNES' RGB signal directly, using an RGB cable.


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PostPosted: Mon Jun 26, 2017 12:07 pm 
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So, it's not possible to change this by, for example, using a different cable?

A related question: If I connected a DVD player over a composite cable while the TV is adjusted to output NES colors correctly, will movies on the DVD look correct or will they look like the SNES with boosted red color?

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PostPosted: Mon Jun 26, 2017 12:16 pm 
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Also, is there a way to calculate how much I have to compensate, so that the SNES image looks correct in relation to the NES image?

Fictitious example:

The colorimetry adds one third of redness to the picture and takes away one tenth of brightness.
So, if you take your TV's color value, divide it by 3 and then subtract this value from the color value: newColor = oldColor - oldColor / 3, then you get the color value that is correct relative to your NES output.
Likewise, you have to do newBrightness = oldBrightness + oldBrightness / 10.


Does colorimetry between RGB and NTSC allow for this kind of calculation or is it all a matter of manually adjusting the values?

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PostPosted: Mon Jun 26, 2017 12:25 pm 
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Quote:
So, it's not possible to change this by, for example, using a different cable?
Use an RGB cable. That avoids NTSC encoding-decoding and with it the NTSC colorimetry assumption.
Quote:
If I connected a DVD player over a composite cable while the TV is adjusted to output NES colors correctly, will movies on the DVD look correct or will they look like the SNES with boosted red color?
Depends on whether the DVD player compensates for NTSC colorimetry or not. If it does not (and I assume most DVD players do not), then yes, DVD reds will get boosted as well.
Quote:
Also, is there a way to calculate how much I have to compensate, so that the SNES image looks correct in relation to the NES image?
Of course it's possible, but it's not feasible, because colorimetry corrections have to be done on linear-light signals, while normal RGB signals are "gamma pre-corrected". To compensate a given R'G'B' signal designed for modern-colorimetry (i.e. Rec. 709) to display correctly on a TV that assumes NTSC colorimetry, first convert RGB values ranging from 0.0 to 1.0 to linear light signals:

[R, G, B] = [R', G', B']^2.2222;

Then apply the appropriate conversion matrix:
Code:
Rntsc=0.6903*R +0.2764*G +0.0334*B
Gntsc=0.0179*R +1.0405*G -0.0584*B
Bntsc=0.0177*R +0.0472*G +0.9350*B


And then back to gamma-pre-corrected signals again:
[R'ntsc, G'ntsc, B'ntsc] = [Rntsc, Gntsc, Bntsc]^0.45.

I'm simplifying, of course; the actual conversion from gamma-pre-corrected signals to linear light signals is more complicated, but 2.222/0.45 exponents are close enough for most applications.

For your convenience, here are a few examples.

NES signal when assuming modern colorimetry:
Image
NES signal when assuming NTSC colorimetry:
Image
SNES signal when assuming modern colorimetry:
Image
SNES signal when assuming NTSC colorimetry:
Image
I'm not sure how closely this matches your TV, but either way, you get the point.


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PostPosted: Mon Jun 26, 2017 1:44 pm 
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Wait? Why did they change the color gamut on TV screens in the first place?


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PostPosted: Tue Jun 27, 2017 8:47 am 
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The modern colorimetric values are exhibited by rare-earth phosphors. Rare-earth phosphors replaced the silicate phosphors of the 1950s, which exhibited NTSC colorimetric values. The silicate phosphors were replaced because they lacked brightness and were long-persistent, leaving trails after moving objects.


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PostPosted: Tue Jun 27, 2017 12:26 pm 
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(More details: http://www.earlytelevision.org/Deksnis/NTSCvsP22.html )


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PostPosted: Tue Jun 27, 2017 3:08 pm 
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Thanks a lot for your detailed information.

You said I should use an RGB cable, so that the colors look right.
But what exactly does an RGB cable look like?

I'm using this cable:
Attachment:
Cable.jpg
Cable.jpg [ 5.45 KiB | Viewed 556 times ]


And my CRT TV only has the composite (yellow, white) port and the standard RF port.
I don't have an actual RGB, SCART or S-video port.

So, when you say RGB cable, what do you mean?


Also (if I still have to use the old cable), when I decrease the color saturation on the TV for the SNES, should I change any other value too? Do brigthness and contrast etc. play into this as well?


And another question: The above cable: Are there differences between the PAL and the NTSC version or is this all the same product no matter where I buy it? And is the cable for SNES and for N64 identical or did they change anything?

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PostPosted: Tue Jun 27, 2017 3:34 pm 
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RGB cable generally means a SCART cable and AV cables do differ between PAL and NTSC units as with controllers. Another layer of region locking that Nintendo practiced.

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PostPosted: Tue Jun 27, 2017 3:37 pm 
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Well, SCART is European. And even though I'm German, my consoles are all original American NTSC devices. Same with the CRT TV that I use to play these consoles.

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