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Sorry for the newbish question, but should the maximum brigthness affect the gamut or not? I have this wonderful plasma that has two somewhat different modes. In one mode its brightness is capped at 120-something, and in another mode it’s twice as much. However profiling two modes doesn’t yield a totally different gamut – it’s still about the same. Why exactly does that happen? What is that that brigtness changes in the color space?
The brightness normally doesn’t affect the chromaticity (much), so the gamut stays about the same. For plasma displays which use phosphors as colorants, much like the old CRTs, the chromaticity of the phosphor isn’t affected much by the insensity of the illumination by the ionised gas that is used to light the (sub-)pixels up, so that explains why the gamut doesn’t change.
Yes, the chromaticity of the phosphors is not affected, but I’m trying to understand where the additional brightness “goes”. I probably should read up on the color science/theory but for this particular aspect, how do we correlate the 2x increase in maximum brightness and unchanged gamut? Surely something becomes different here, the luminance range is expanded, for one… I’m trying to wrap my head around those two concepts and why they don’t affect each other.
In my uneducated/layman view if I display a bright orange on a bright display and then compare the same shade on a dim display, wouldn’t the same hue turn out to be “grayer” than the first one, relatively?the luminance range is expanded, for one
Unless you have an display with perfect “zero” black level (e.g. OLED), no. The black level rises along with the white level, so contrast and luminance range stays the same unless you limit brightness at the digital signal level.
if I display a bright orange on a bright display and then compare the same shade on a dim display, wouldn’t the same hue turn out to be “grayer” than the first one, relatively?
Not ‘grayer’ which would imply a change in chroma, but ‘blacker’. The perceived intensity will be less, but only if you put the displays next to each other, or if the viewing environment is too bright for the ‘dim’ display. That’s also the reason why the peak white level should be chosen in relation to the viewing conditions. The human visual system adapts to a wide range of illumination levels, but unless you go very dark (mesopic or even scotopic vision), color perception doesn’t change that much because the contrast range the eye perceives stays the same.
Yes, it makes sense now so thanks for the explanation! And it’s an interesting remark about the mesopic vision because it covers a strict certain luminance level for a particular individual, so basically every color beyond a certain luminance threshold will be processed differently. Not sure if that really applies to displays (need to dig up the luminance data) but that could be one reason why luminance matters and why in theory a dimmer display’s darker colors will be perceived differently than the same colors but with a higher luminance level.
I guess a fitting analogy would be with sound waves and sound reproduction: sound quality and resolution in both dimensions will stay the same regardless of the volume if being controlled in the analog part of the chain, same with luminance.And it’s an interesting remark about the mesopic vision because it covers a strict certain luminance level for a particular individual, so basically every color beyond a certain luminance threshold will be processed differently.
Note that for mesopic and scotopic vision to occur, the overall light level needs to be below the respective thresholds for prolonged periods of time. It doesn’t usually ocur when looking at a display because even a very dim display will be far too bright. Scotopic vision is in essence b&w, there is no color discrimination.
that could be one reason why luminance matters and why in theory a dimmer display’s darker colors will be perceived differently than the same colors but with a higher luminance level.
Well that’s the point, they won’t unless directly comparing the two (assuming chromaticity really is the same).
