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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 2:26 pm

Joined: Mon Dec 29, 2014 1:46 pm
Posts: 911
Location: New York, NY
Dwedit wrote:
Here's the YIQ color plane.
Cut it up into 12 sections (cut each quadrant into thirds), and give it 4 levels of brightness.

What about the grays and the blacks?

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 2:27 pm

Joined: Sun Jan 22, 2012 12:03 pm
Posts: 7460
Would it have been feasible to divide into 15 rather than 12, or is there something inherent about "quadrants" that makes a multiple of 4 work better? e.g. could you have easily done 16 hues if you gave up white/grey/black?

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 2:55 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 8362
Location: Seattle
Even numbers work better. (More precisely: Designing something that works reliably at frequencies below 30MHz is much easier. Even divisors let you use both rising and falling edges of the clock usefully.)

The Commodore 16 and Plus/4 provided access to a subset: 14 angles of the 16 equally-spaced division of the YUV plane.

I previously contemplated a design that used a 7×NTSC crystal instead. This gives you 14 equally-spaced divisions of the YUV plane.

But with both of these, you can't easily synthesize the 5.4MHz pixel clock any more. Other choices have other compromises, which may be better (more nearly square pixels) or worse (needing more nametable memory or pillarboxed display).

edit: (An 8× crystal would afford a pixel clock of NTSC×8÷5, a 272 pixel mode with a PAR of 15:14. A 7× crystal would afford a pixel clock of NTSC×7÷4 or ÷5, yielding a 296 pixel mode with a PAR of 48:49 or a 240 pixel mode with a PAR of 60:49)

Last edited by lidnariq on Mon Jun 12, 2017 3:08 pm, edited 1 time in total.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 3:04 pm

Joined: Sat Feb 12, 2005 9:43 pm
Posts: 11345
Location: Rio de Janeiro - Brazil
rainwarrior wrote:
Would it have been feasible to divide into 15 rather than 12

Look at the palette of the Atari 2600. The TIA is such a simple chip that I can't imagine that's a hard thing to pull off... Based on the master palette alone, the NES really looks like a step back from the 2600.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 3:14 pm

Joined: Sun Apr 13, 2008 11:12 am
Posts: 8362
Location: Seattle
The TIA implements the ÷15 as a series of carefully-tuned analog delays from the original NTSC colorburst frequency crystal. When it came to the PAL revision, they gave up retuning the inverters and only gave you 12 angles instead.

It's much harder to move analog designs from one IC fabrication facility to another; often every carefully-tuned R and C need to be revisited when you do so. A purely-digital design, or at least one where the only values that matters is the ratios of specific resistors relative to each other (such as the 2A03's DACs), means it's a lot easier to move fabs as demand changes.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Mon Jun 12, 2017 3:40 pm

Joined: Mon Nov 10, 2008 3:09 pm
Posts: 433
lidnariq wrote:
The TIA implements the ÷15 as a series of carefully-tuned analog delays from the original NTSC colorburst frequency crystal. When it came to the PAL revision, they gave up retuning the inverters and only gave you 12 angles instead.

It's much harder to move analog designs from one IC fabrication facility to another; often every carefully-tuned R and C need to be revisited when you do so. A purely-digital design, or at least one where the only values that matters is the ratios of specific resistors relative to each other (such as the 2A03's DACs), means it's a lot easier to move fabs as demand changes.

The Atari machines have a potentiometer on the motherboard for adjusting the analog-generated hues. They were supposed to be tuned at the factory with the aid of a test-pattern cartridge, but in practice, especially as the components age, hue 15 (the one with the longest delay) ends up varying between units from orange to green--and that's in addition to the inevitable variability between NTSC TV sets.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 12:41 am

Joined: Fri Nov 12, 2004 2:49 pm
Posts: 7711
Location: Chexbres, VD, Switzerland
tokumaru wrote:
Look at the palette of the Atari 2600. The TIA is such a simple chip that I can't imagine that's a hard thing to pull off... Based on the master palette alone, the NES really looks like a step back from the 2600.

I ought to disagree strongly. The NES palette is pure genius, I think. I love how the colours are fully saturated, it makes the game appears more bright and shallow than on any other console of the era. And they did that using a simple Johnson counter technique to realise the NTSC encoding ! The only complaint I'd have is that they should have used 14 or 15 hues instead of only 12, and I'd have liked one additional level of gray darker than palette \$00, but who cares.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 2:06 am

Joined: Sat Feb 12, 2005 9:43 pm
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Location: Rio de Janeiro - Brazil
I ought to disagree strongly.

The 2600 has yellow and 8 brightness levels, period.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 3:11 am
 Formerly WheelInventor

Joined: Thu Apr 14, 2016 2:55 am
Posts: 2017
Location: Gothenburg, Sweden
Quote:
as the components age

Can i assume this specifically means capacitors drying out? That sounds the most likely to me. Had they been produced today, and depending on application, there's types of caps with much tighter consistency over long time of use and storage, if somone were to reproduce the model, or if a new 'retro' console was made.

On a per unit level, discrete caps should be easy to replace.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 3:50 am

Joined: Fri Nov 12, 2004 2:49 pm
Posts: 7711
Location: Chexbres, VD, Switzerland
tokumaru wrote:
The 2600 has yellow and 8 brightness levels, period.

Which leads to another fallacy than "the NES has more blues" - the NES indeed DOES have a yellow colour; the \$x8 column is indiscutably yellow to me. It is hower true it is the only column with yellow tones, as the \$x7 column is already leaning towards orange and colour \$x9 already leaning towards green, although both are yellow-ish. The saying that the NES "doesn't have yellow" is complete bullshit - it just have 12 equally spaced hues, and it just happens the word "yellow" seems rather restrictive to the proposed hues.

Besides, you know the 2600 looks absolutely awful, no matter it's colour palette - for other reasons, mainly the awfully low resolution.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 5:54 am
 Formerly WheelInventor

Joined: Thu Apr 14, 2016 2:55 am
Posts: 2017
Location: Gothenburg, Sweden
Colours are never indiscutable to me . I consider 26 to be peach, 27 orange/amber, 28 overmature lime. None is actual yellow (as in lemon or Trollius altissimus), but all could be categorized as yellows when thinking in overlapping terms, just as "blue" might overlap violet and teal. The slices of the master palette cuts straight through some cultural definitions, while cutting in-between some other.

Attempt at categorizing:

x1 Cold blue
x2 "Almost pure" Floral Blue* (but really, i think 'pure' is between x1 and x2)
x3 Violets
x4 Purples
x5 0: (Dark) Cerice | 2: Cerice/hot pink**
x6 0: Off-red/wine | 1: the colour of light polution a cloudy night over a city with warm street lights | 2: Peach
x7 0: Brown 1: Mustard Seed | 2: Orange Or all of them: Amber or Citrine
x8 0-1: Olive | 2: Overmature lime
x9 Green lime
xA "Pure" Green
xB 0: Jade/Pine | 1: Cold Green | 2: Mint
xC 0: Navy/Teal (darker) | 1-2: Teal (brighter)

the 4x are simply categorized as bright pastels of the same to me.

*"Blue" flowers tend to be "almost blue", but lean slightly towards the violet upon closer inspection. Few are true blue or indigo; one exception is usually the hard-to-grow "Lingholm" variety of Meconopsis, but even then, some individual plants may develop violet streaks.

**Not named so after tint but after cultural affect. Picture-googling "hot pink" will reveal a variety of pinks, of which most lean towards the cold. It's also interesting to see what items and contexts such a colour is associated with. That goes for any colour.

It's not complete, perfect or universal. Different TV sets will shift the tint aswell. Just an attempt to formalize categorizations i half-consciously work with when pushing pixels.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 10:21 am

Joined: Sat Feb 12, 2005 9:43 pm
Posts: 11345
Location: Rio de Janeiro - Brazil
Besides, you know the 2600 looks absolutely awful, no matter it's colour palette

A lot of people would say the same about the NES depending on which consoles they grew up with and their personal preferences. While it's true that the majority of all 2600 games look like shit (by today's standards, at least), I believe that it's possible to create captivating graphics on any platform (yes, even on the ZX Spectrum). A good artist who embraces the limitations of each console can succeed in any platform.

I mean, just look at Alp's Intellivision mock-ups in this thread. Nothing remotely as good looking as that was previously released on that console. His Atari 2600 stuff isn't too shabby either!

Your dislike for the 2600 is very clear, but there's just no denying that 15 hues at 8 brightness levels is objectively better than 12 hues at 4 brightness levels. And the gray column on the 2600 doesn't have any weirdness like repeated colors.

I love the NES, but its master palette is undeniably one of its weaker points, along with the small number of sprite and background palettes (and the 8 sprites per scanline limit, but that's beside the point).

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 10:34 am

Joined: Sun Sep 19, 2004 11:12 pm
Posts: 21389
Location: NE Indiana, USA (NTSC)
tokumaru wrote:
I believe that it's possible to create captivating graphics on any platform (yes, even on the ZX Spectrum).

Case in point: The Trap Door uses characters large enough that two colors per 8x8 pixel color area aren't quite as limiting. (Video)

And when Alp can come up with Intellivision graphics that wouldn't look that out of place on a Game Boy Color, that illustrates your point.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 11:08 am

Joined: Sun Apr 13, 2008 11:12 am
Posts: 8362
Location: Seattle
FrankenGraphics wrote:
Can i assume ["as the components age"] specifically means capacitors drying out?
I think it's actually something inside the TIA's die... maybe the MOSFET-used-as-a-capacitor. Or maybe the two enhancement-mode 'FETs...

The NTSC 2600's schematic starts with a BJT-based 3.57MHz crystal driver. The external tuning potentiometer actually adjusts a bias voltage for the inverters inside the TIA (see page 5).

the NES indeed DOES have a yellow colour; the \$x8 column is indiscutably yellow to me.
1: On NTSC, \$x8 is pure shade -U, which is not yellow. Yellow is defined as 13° clockwise from shade -U. See also my composite image in this old post.
2: PAL NES and NTSC NES have different master palettes, offset by a 15° rotation in the YUV plane. Shade \$x8 on 2C07 is basically yellow. Shade \$x8 on 2C02 isn't.

tokumaru wrote:
there's just no denying that 15 hues at 8 brightness levels is objectively better than 12 hues at 4 brightness levels
The PAL and NTSC 2600s also have different master palettes. The PAL 2600 only has 12 hues.

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 Post subject: Re: Why only 52 colors instead of 256?Posted: Tue Jun 13, 2017 11:33 am

Joined: Sat Feb 12, 2005 9:43 pm
Posts: 11345
Location: Rio de Janeiro - Brazil
Yeah, they certainly screwed up the PAL 2600 palette (not nearly as badly as with the SECAM version, WTF is up with that?!?), but it might still be better than the NES' due to having more brightness steps.

Here's a comparison between the different Atari 2600 palettes, for those who're not familiar with the system:
Attachment:

98874793.jpg [ 106.96 KiB | Viewed 1654 times ]

The reason I keep bringing the 2600 up is because it's significantly older than the Famicom, and the design of the TIA is incredibly simple, so I find it somewhat surprising that Nintendo came up with something with worse color capabilities.

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