Role of sensor in color rendering?

Started 3 months ago | Discussions thread
57even Forum Pro • Posts: 14,505
Re: Role of sensor in color rendering?

JimKasson wrote:

57even wrote:

JimKasson wrote:

57even wrote:

JimKasson wrote:

57even wrote:

Tri-stimulus colour spaces don't replicate human vision either

Please explain.

Are you talking about:

  • Departures from color-normalcy?
  • Variations in color responses within the color-normal range?
  • Spatial effects?
  • Adaptation?
  • Non-physical primaries?

Or something else?

I am talking about the fact that a large range of colours we can see is not reproducable on any RGB or CMY based colour device, and on sRGB, about 64% of them.

So you are talking about the available devices, not tristimulus color spaces in general. XYZ is certainly a tristimulus space, and can encode all the colors that the standard observer can see. It does, however, have non-physical primaries.

I was under the impression that tristimulus implied three visible colours (CIE RGB) rather than unreproducable virtual colours that don't have a corresponding wavelength.

I've never used it that way. I've not seen others make that distinction. Here's an example of the usage that I've seen:

A pertinant quote: "The CIE XYZ color space encompasses all color sensations that are visible to a person with average eyesight. That is why CIE XYZ (Tristimulus values) is a device-invariant representation of color.[5]"

For enough. I was misinformed, but I don't find it very satisfactory.

By the way, I don't think you meant to use the word "colours" after "unreproducible". If you can't see it, it's not a color.

I meant it is a radiation frequency that cannot be produced (visible or not) so there is no way to recreate the colours in CIE XYZ (even accounting for the invisible non colours) using any three actual physical means.

Good sensor colour science (closer to LI) is less import with smaller gamuts, but becomes more problematic with large ones, like the future Rec.2020 standard.

I wouldn't say that the color science of a LI sensor is in any global way better than that of the sensors that we have. The people who design those CFAs know how to get close to LI, but they choose not to because of the sensitivity and SNR issues of LI CFAs. Not sure I agree about the larger gamut making the situation worse, since the memory colors tend to lie within Adobe RGB.

While it's true that most OOG colours are cyan tones, red/blue response can have a fairly serious impact on colours along the line of purples.

Sure, it may not be a big deal, but AdobeRGB red (for example) is distinctly more orange than DCI-P3. Filter designs assuming AdobeRGB as an output space may not cut it in future.

I see no evidence of that, from looking at the numbers. But I can't disprove your speculation. There's a likely exception, and that's spectral primaries,

If the spectral primaries define the extent of the space and therefore the red channel hue, I would have thought that was a problem.

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