Talk:Color depth

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Contents 1 Images 2 Indexed Color 3 Beyond True Color 4 RAW format 5 Dubious 6 10bit - Matrox Parhelia 7 16-bit colour

[edit] Images

I uploaded a photograph at different color depths, but I am very displeased with my formatting. If someone could reformat these images without destroying detail, I would be grateful. The problem with putting the pictures in a gallery or making them smaller thumbs is that the computer rounds (if that is the correct word) some of the colors, creating shades of grey in a b&w image and colors that do not exist in the color depth, etc. Thegreenj 21:59, 12 February 2007 (UTC)

This page needs cleanup. The Direct color section is a haphazard, unorganized list of color depths. I don't know how, but that needs to be cleaned up. --Josh Lee 21:31, Jan 21, 2005 (UTC)

Err, This page looks messy in Safari. Getting some overlapping links where scanner colour bit depth is explained. Anchor links malfunction too. Think it has something to do with these floated images, but unsure. FYI. george.

[edit] Indexed Color

This section gives the feeling there is only PC graphics card in the world... --Diego 13:14, 20 June 2006 (UTC)

[edit] Beyond True Color

This article begins discussing color depth in terms of Bits Per Pixel. However, the "Beyond True Color" section introduces the term Bits Per Channel. In this context, what does channel refer to? I am assuming that channel refers to the individual colors in a pixel, RGB. Therefore, would 24 bits per pixel = 8 bits per channel? So when this section states that human vision can see at best about 10 bits per channel, would that be equivalent to 30 bits per pixel? - Unsigned

This whole section needs a lot of work. This paragraph, for instance is both poorly worded, and misleading:

"For extended dynamic range imaging, including high dynamic range imaging (HDRI), floating point numbers are used to describe numbers in excess of 'full' white and black. This allows an image to describe accurately the intensity of the sun and deep shadows in the same colour space. Various models are used to describe these ranges, many employing 32 bit accuracy per channel. A new format is the ILM "half" using 16-bit floating point numbers, it appears this is a much better use of 16 bits than using 16-bit integers and is likely to replace it entirely as hardware becomes fast enough to support it."

First of all, floating point numbers don't describe numbers "in excess of 'full' white and black." Rather, they allow for a less discrete distribution of tones *between* white and black, which enables you to record detail more accurately. Wording like "it appears" shows a lack of conviction about the data. The bit about ILM seems to refer to Industrial Light and Magic, who developed the OpenEXR format. If it is in fact discussing OpenEXR, why not say that, rather than ILM? It's confusing even to me, and I use HDR imaging in my every day work as a pro photographer. Dilvie 04:22, 20 April 2007 (UTC)

Another reason further work is needed is that it suggests that anything beyond 8 bits per channel is unusual based on the number of colours available (3 times 2 to the power of 8). However, 16 bits per channel is now widespread and important in photographic manipulation software. The benefits are very clear: when tonal areas are 'stretched', using curves facilities (almost standard in advanced photographic image manipulation) 8 bits easily split shades into easily distinguishable areas, like a shaded contour map (aka 'posterisation'), losing the original smooth transitions. 16-bit colour images cabn be subjected to substantially more use of curves before the posterization effect occurs.

[edit] RAW format

This page should mention RAW camera formats since one advantage many such formats provide is 12-bit-per-channel color. —Ben FrantzDale 13:33, 19 October 2006 (UTC)

[edit] Dubious

I added the dubious tag as some of the stuff there sounds like misleading marketing to me. I came across this discussion [1]. While not a reliable source, I'm pretty sure that what they're saying there is right. There is no instrinsic reason why you can't produce correctly saturated yellow from red and green. Simple physics and an understanding of the human visual system should tell you this. You may or may not be able to achieve this in practice at the current time, but suggesting it's an approximate is misleading. Nil Einne 16:56, 1 August 2007 (UTC)

Actually, the article text is correct, or at least has the right idea. The physics is not so simple. The complete spectrum of the human visual system can not be entirely represented by combinations of only three primary colors. For any "mixed" (non-primary) color, the saturation will not be as great as for a monochromatic light source of the same color. No matter what three primaries you pick, the gamut will not completely span the entire color space.

If you're not familiar with colorimetry, some diagrams might help: Look at this diagram and this diagram. In those diagrams, a color is described by its x-y coordinate and is represented by a point. The color's saturation is measured by the closeness of the color coordinate to the outer monochromatic line. If you choose three primary colors, then all possible mixtures of those primaries are contained in the triangle formed by the three primaries' color coordinates; the triangle is called the gamut. No matter what three primaries you pick, you'll always leave out part of the visible range. (To be more precise, the only way to have three primary colors that span the entire color space is to use so-called "imaginary" colors, which essentially make use of "negative brightness," a mathematical trick that results in non-realizable primaries.) For more details, see CIE 1931 color space, especially this section.

I removed the dubious tag and added a citation to support the article text. -- WakingLili (talk) 18:55, 16 August 2007 (UTC)

[edit] 10bit - Matrox Parhelia

Didn't the Matrox Parhelia graphics card support 10bit colour depth? I would have added this fact, but I do not feel I understand enough of this topic to make a definitive contribution.

[edit] 16-bit colour

The statement that “many Macintosh systems” support[ed] 65536 colours is incorrect. All “16-bit” Mac graphics use (and have always used) 15-bit colour with one bit of padding, providing 32768 colours. On the other hand, I believe Windows supports 16-bit colour (5 bits R, 6 bits G, 5 bits B). I don’t have any sources for this offhand, but then, neither does much of anything in the article. Also, these modes are direct colour, not indexed colour. -213.115.77.102 (talk) 13:46, 10 January 2008 (UTC)