Talk:RGB color model

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[edit] Subject: Psychological Primary Colors

The "red" and "green" that the R and G were named after in RGB are actually more yellow than pure red and pure green, defining such as being neutral on the blue-yellow scale, which are 2 of the 6 psychological primary colors. The psychological primary colors and their RGB coordinates are:

Red = 255 0 128

I just opened up an xterm with that color and it looks sort of pink. If I just use 255, 0, 0, it looks red. Michael Hardy 02:21, 18 Feb 2004 (UTC)

Yellow = 255 255 0 Green = 0 255 128 Blue = 0 0 255 Black = 0 0 0 White = 255 255 255

Of course, gray is 128 128 128; note that it is a mixture of any 2 colors that are complements, such as black and white, blue and yellow, and red and green. How about the secondary colors

Red + Yellow = Orange (255 83 0) Yellow + Green = Lime (83 255 0)

This is ridiculous: orange and lime are disambiguation pages, not pages about colors!! Michael Hardy 02:24, 18 Feb 2004 (UTC)

Green + Blue = Sea Blue (0 172 255) Blue + Red = Purple (172 0 255)

Anything + Black = half the distances between the coordinates and 0 Anything + White = half the distances between the coordinates and 255

See also the messages at Color, Red and Primary Color that also have to do with psychological primary colors.

Why link to Primary Color with a capital "C" when no such page exists, and you could link to primary color with an appropriately lower-case "c", which does exist? (The capitalized page now exists as a redirect page; I just created it.) Please check your links to see if they're working right!! Michael Hardy 02:28, 18 Feb 2004 (UTC)

[edit] History of RGB color model - RCA, Edwin Land ...

Would it be possible to include some history of the use of the RGB color scheme - including for example, the RCA standards for color television that were adopted in 1953, Edwin Land's use of an RGB scheme for the Land / Polaroid camera and the introduction - and subsequent adoption by W3C in HTML 3.2 - of color="#rrggbb" as the Internet standard for the presentation of color.

I would also like to offer a link that perhaps might be included in the RGB color model, namely http://www.peace-cubes.net, the home of the Virtual Light and Colour Cubes - defined as virtual entities with dimensions of red, green and blue, in which the color at any point is the sum of the red, green and blue coordinates, where color="#rrggbb" is understood as an arithmetic expression in a three-dimensional mathematics of light and color.

Yhe Virtual Light and Colour Cubes were dedicated as Peace Cubes at the United Nations Peace Bell on March 20, 1997 - see http://habitat.igc.org/peace-cubes/dedicate.htm - and have served as icons for the transition to a digital knowledge-based universe in which we can see the world in transformed and transformative ways, and as a reminder of the existence of one light in all of creation - in the digital world as well as in material realms.

Robert Pollard
Information Ecologist & Digital Artist
ecology2001@mindspring.com
Information Habitat: Where Information Lives - Home of the Virtual Light & Colour Cubes
http://habitat.igc.org/

This looks like a semi advert. I'm at loss whether to delete it or keep it Kim Bruning 16:25, 9 Apr 2004 (UTC)

[edit] Article has a slight POV slant

...in favor of 8 bits per channel. What about methods that represent RGB as floating point proportions (like OpenGL does, IIRC) or that represent RGB in *more* than 8 bits per channel (I'd imagine specialised applications or simply photo editing where that'd be important).

Hmm. Kim Bruning 16:20, 9 Apr 2004 (UTC)

given that (at normal viewing distance and resolution) only four bits are actually needed for green, ~3.5 for red, and 2 for blue, suggesting that more bits bit be useful could be misleading. 8 bits per channel is a convenience (as it means some image processing calculations can be done more simply), and the same is true for using floating-point values, but all those extra bits are a bit of an indulgence :-) mfc

Who cares about the human visual system?

  • Extra bits are useful for more accurate measurements for scientific purposes.
  • Natural lighting can have a massive dynamic range.
    • Even if the human eye can only grab a subset of that range, doesn't mean there might not be a reason to record light levels across the entire range (and then later be able to pick out cross-sections from that range to view different parts of our recording).
    • Have you ever noticed how many rendered images look so flat? This is especially true of "outside pictures".It'd help if those rays actually were traced at a higher color-depth. You could then select your viewing pane coordinates in color space* as well as euclidian space. This would be akin to setting the light sensitivity (ISO value && partially also diafragma) on your virtual camera. (Hmm, I'd actually have to look up to see if some renderers don't already do that.)
  • When editing in the colorspace of a photo, sometimes I just run out of bits! Arrrgh, bother, time to retake that photo. If the camera had just been able to record at just a little more colordepth , I could have managed. (This is related to my hard-disk always having juust too little space for those images to fit too. :-P )
    • Fortunately, some cameras already have a raw output format at 16 bits per channel. :-) Unfortunately these are almost always proprietary. :-(

Hope this gives a bit of an idea why a larger color-space might be useful. :-) Kim Bruning 18:55, 9 Apr 2004 (UTC)

* in a way that would actually be meaningful.

[edit] 0.0...1.0 vs. 0%...100%

There has been a small disagreement on whether we should explain, and if so, how we should explain the difference/conversion between the two representation of a color's intensity, as per the section title.

The initial version of the article read:

  • Color science talks about colors in the range 0.0 (minimum) to 1.0 (maximum). Most color formulae take these values. For instance, full intensity red is 1.0, 0.0, 0.0.
  • The color values may be written as percentages, from 0% (minimum) to 100% (maximum). To convert from the range 0.0 to 1.0, just multiply by 100. Full intensity red is 100%, 0%, 0%.

The first paragraph never changes throughout the mini-dispute, so I won't repeat it. An edit made by 67.83.133.218 added a percent sign after the "100" you should multiply with. His/her comment in the history: "You multiply by 100%, not 100. 100% == 1, you aren't actually doing anything." The result was:

  • The color values may be written as percentages, from 0% (minimum) to 100% (maximum). To convert from the range 0.0 to 1.0, just multiply by 100%. Full intensity red is 100%, 0%, 0%.

Now that looks kind of silly to me, explaining to people they have to multiply by 100%, it looks like we don't know what we're talking about. Moreover, I think people need to take an arithmetic lesson if they want to find out how to "convert" 1.00 to 100%, instead of reading an article about RGB. Taking things to extreme, should we also include information about how to power up their computer in this article, in order to start Photoshop or whatever? Anyway, based on that rationale, I removed the conversion phrase altogether, leaving us with:

  • The color values may be written as percentages, from 0% (minimum) to 100% (maximum). Full intensity red is 100%, 0%, 0%.

Notinasnaid however said "I have to disagree: this is a very common cause of total confusion among people working with color. If it's confusing, please rephrase, but the explanation is important, I think.", and after a couple of edits we now have:

  • The color values may be written as percentages, from 0% (minimum) to 100% (maximum), or sometimes just 0 to 100 without a percentage sign. To convert from the range 0.0 to 1.0, just multiply by 100. Full intensity red is 100%, 0%, 0% (or just 100, 0, 0).

I have to say I never saw the 0 to 100 range for colors... 0% to 100%, yes, that I have, and 0..255 as well--but 0 to 100, never. For the time being, I'll simply revert to my deleted version. If someone can come up with a situation where 0 to 100 is actually used in a mainstream product to represent 0..100%, please comment here. --Gutza T T+ 09:47, 28 July 2006 (UTC)

I agree – it's quite unnecessary to spell out that 1 × 100 → 100. (And plain 100 would be very unlikely for a numerical value, anyway, it would more probably be 0→99. quota 12:12, 28 July 2006 (UTC)

Hummm... maybe Notinasnaid was right after all... quota, 1.00 is 100%, you don't "convert" between them because they already are the same thing. --Gutza T T+ 12:32, 28 July 2006 (UTC)

As a compromise version, which tries to clarify things without making the editors look bad, I ended up with this version:

  • The color values may be written as percentages, from 0% (minimum) to 100% (maximum). To convert from the range 0.0 to 1.0, see percentage. Full intensity red is 100%, 0%, 0%.

--Gutza T T+ 12:40, 28 July 2006 (UTC)


  • You write "Moreover, I think people need to take an arithmetic lesson if they want to find out how to "convert" 1.00 to 100%" and I might be inclined to agree, but people really don't understand what they have, and that they are numbers they can do arithmetic with. Let me share with you an exchange I recently witnessed in a discussion forum. Person A: The colours you quote are in the range 0 to 255. [The context] expects colour components to be in the range 0 to 1. So conversion is straightforward.. Person B: Could you please share how you would convert the RGB value of "233, 217, 145" ? I'm just not getting the straightforward part. It would be good if Wikipedia was comprehensible to people without too much background knowledge. What we have now is OK, but maybe a little table explaining how to convert between each representation would not be too far wrong. When something is easy, it's easy to forget how hard some people can find it. Notinasnaid 20:19, 28 July 2006 (UTC)

Please note I didn't comment on converting 0..1 or 0%..100% to/from 0..255. All of this revolved around the conversion between 0..1 and 0%..100%. I think the current version regarding that part is quite clear, especially since the percentage article starts off with a very clear explanation that 0%..100% is actually the same range as 0.0...1.0. --Gutza T T+ 20:53, 28 July 2006 (UTC)

[edit] Color vision

somebody said that the eyes can see 3 different colours.. yellow-green, and two others.. can we get a representation of these particular colours?

That wouldn't belong in this article, but might belong in color vision. Notinasnaid 07:24, 30 August 2006 (UTC)
The three colors happen to be... drumroll... RED, GREEN, and BLUE! -SharkD 14:13, 22 October 2006 (UTC)
Nevermind. I was wrong. -SharkD 04:53, 18 November 2006 (UTC)

[edit] 3D rendering of RGB cube

I did a 3D rendering of the RGB cube in POV-Ray. Wasn't sure where to put it, so I'll just put it here instead. -SharkD 14:15, 22 October 2006 (UTC)

[edit] Orphaned article

The article that appears at http://en.wikipedia.org/wiki/RGB_color_model is slightly different to that at http://en.wikipedia.org/wiki/RGB. The RGB article claims to redirect to the RGB color space article, yet has its own page with independent content. As an inexperienced user of Wikipedia, I'd like to know why this is, and what can be done about it.

RGB and RGB color model do seem to be the same article. What differences can you see? RGB color space is an entirely different article. This is as it should be, but one of the great challenges is to make it clear why it should be. Notinasnaid 10:40, 23 October 2006 (UTC)
Should RGB color space be added to the navigation table at the bottom of the page? -SharkD 06:32, 25 October 2006 (UTC)

[edit] RGBA and camera's

A small section about digital camera's has been added to the RGBA section. This seems to not belong there. Does it even belong on this page? -- Peter 12:50, 13 November 2006 (UTC) do not play around with theses notes. thank you!

[edit] 24-bit color image?

I have a question, does anyone know where i can find an image containing all 24-bit colors? —The preceding unsigned comment was added by 168.216.109.213 (talk) 18:31, 8 January 2007 (UTC).

Thanks for the good cube pic, helped me on my school project.

[edit] Questions

I'm not an expert in this, but I guess the image (VEN DIAGRAM kind) should have black in the centre and not white. Sorry if thats too silly. 128.240.229.66 14:26, 21 February 2007 (UTC)

Sorry it was me Wikiality who posted the above message without realising am not logged in. Just to let know where you can find me. Cheers Wikiality 14:29, 21 February 2007 (UTC)

No, white in the middle is right because white light is made up of all colors. My question is, shouldn't the first cube have a white block in the middle instead of grey? ImMAW 01:00, 13 March 2007 (UTC)

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