Can changing RGB primaries extend a display’s gamut toward violet?
Asked 7/11/2020
3 views
2 answers
0
If an RGB display or projector uses a shorter-wavelength blue primary (shifted closer to violet), would that expand the range of visible colors it can reproduce in the violet region? More generally, can moving RGB primaries increase gamut coverage, and if so, why don’t common display color spaces simply push the blue primary farther toward violet?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
6y ago
2 Answers
3
Yes but you do not even need to.
The color gamut indicated by the triangle is the coverage of linear combinations of the three RGB primaries. By moving the primaries you can expand or contract the color gamut. This can be seen if you compare the sRGB and Adobe RGB color spaces, both are RGB with slightly different primaries.
Theoretically, you can move the primaries anywhere. The reason though they are not simply moved really wide apart is to avoid banding due to quantization. While mathematically any color within the color-space is part of it, when using fixed color-depth, not all exact colors are representable. So a wider color space has larger steps in between colors and therefore is more likely to show banding and other color artifacts.
Given modern advances, one can use deeper pixels and even floating point respresentation which allows for a wider color-space while minimizing quantization errors. Take a look at the difference with ProPhoto RGB that does something similar to what you suggest:
Source Photography Life
Once colors can be represented by non-integers, the next step is to allow negative values. This is easy to store in floating point numbers but is also used with fixed-point numbers. The sRGB64 color-space, now renamed scRGB, does exactly this and achieves an extremely wide color-gamut that covers nearly the entire visible light spectrum because each component can from around -0.5 to 7.5 as a factor multiplying a primary. See the diagram in the Wikipedia articled.
Originally by user1620. Source · Licensed CC BY-SA 4.0
user1620
6y ago
0
Generated from our catalog & community — verify before relying on it.
Yes. In an additive 3-primary system, the gamut depends on the chosen primaries, so moving a primary can expand or reshape the reproducible color range. That’s why different RGB spaces such as sRGB and Adobe RGB have different gamut coverage.
Shifting the blue primary toward shorter wavelengths can extend coverage toward violet. But there are tradeoffs: with a fixed bit depth, a wider gamut spreads the same number of code values over a larger range, which can increase visible quantization/banding unless higher precision is used.
Also, display gamut and camera sensor response are different topics: cameras don’t inherently “have” an RGB gamut in the same way a display color space does. The output color space is chosen later in processing.
Finally, human vision can be “tricked” into perceiving violet-like colors from mixtures of longer wavelengths, so displays can produce colors we call violet even without emitting true spectral violet. In practice, RGB primaries are chosen as a compromise among gamut, precision, efficiency, and practical display design rather than simply pushing one primary as far as possible.
Recommended products
UniqueBot
AI6y ago
Your Answer
Related Questions
Why do displays use RGB subpixels instead of a pixel that can emit any wavelength?
How can I measure my monitor’s sRGB and Adobe RGB coverage percentage?
Why do printed CMYK blues look less saturated than sRGB on a monitor?
Can I safely edit Adobe RGB images on an sRGB-only monitor?
How can I create a turquoise/teal color grade in darktable similar to Lightroom?