by Lotz » Sat Dec 17, 2022 8:10 am
Chris Peterson wrote: ↑Fri Dec 16, 2022 10:05 pm
You misunderstand me. The wavelength of Ha contains no green or blue signal from typical display primaries. It can only be represented by red. Imperfectly, of course. There are emission lines from different species that we can see as different with our eyes (say, with a gas tube) that cannot be rendered as different on a monitor.
Unfortunately, I have again to dissent here. You missed one important point of color synthesis in display systems. If we'd say, pure red is the best, how you could represent Ha on a monitor, than, on the other side of the spectrum, pure blue would be the best way to represent violet. Violet, however, can be very good approximated by blue with some addition of red. On the other side of the spectrum, to approximate red longer than the primary stimulus is, you have to add some blue.
Thats the concept of the color triangle and the basis of additive color mixing. For sure, physically, you get a red emission peak and a blue emission peak, but based on the ratio of those peaks you get something looking like longer red or shorter blue (i.e. violet).
Coming to your gas tube example: I totally agree, there will be wavelength pairs, which you can not render differently on a screen, but there will be also wavelengths pairs, which you can clearly render differently on a monitor, That only depends on where in CIE1931 those pure colors are located, how far they are separated and how large the color depth of your imaging system is. But selling OIII somewhere between violet blue and acid green, depending on who made the image, is somewhat odd.
I am quite sure, this is, what you mean, when saying color is physiological. It looks e.g. violet, but indeed is just a blue and a red emisison peak. The same is for white: it can be synthesized by 3 very narrow peaks, but could as well be a broadband continuum. But that's how our visual apparatus works and has nothing to do with color itself. Coming to Ha or OIII ( whose hue is at least not outside the color triangle, and therefore maybe more intuitive): There is exactly ONE (R;G;B) triple (with R being zero in the case of OIII), that generates a color hue, which is a best fit to the color hue of a pure OIII emitter. It's for sure not perfect - I clearly state in my paper, that narrowband emitters CAN NOT be perfectly represented on any kind of currently available imaging devices - but it is the best approximation for those colors and there is an explicit color tupel for each wavelength and each color gamut. Yes, it is not perfect, as I stated in my paper, but those colors (a) give consistentcy and (b) when displayed on a monitor have the least deviation from the real emitter.
CS
Markus
[quote="Chris Peterson" post_id=327849 time=1671228335 user_id=117706]
You misunderstand me. The wavelength of Ha contains no green or blue signal from typical display primaries. It can only be represented by red. Imperfectly, of course. There are emission lines from different species that we can see as different with our eyes (say, with a gas tube) that cannot be rendered as different on a monitor.
[/quote]
Unfortunately, I have again to dissent here. You missed one important point of color synthesis in display systems. If we'd say, pure red is the best, how you could represent Ha on a monitor, than, on the other side of the spectrum, pure blue would be the best way to represent violet. Violet, however, can be very good approximated by blue with some addition of red. On the other side of the spectrum, to approximate red longer than the primary stimulus is, you have to add some blue.
Thats the concept of the color triangle and the basis of additive color mixing. For sure, physically, you get a red emission peak and a blue emission peak, but based on the ratio of those peaks you get something looking like longer red or shorter blue (i.e. violet).
Coming to your gas tube example: I totally agree, there will be wavelength pairs, which you can not render differently on a screen, but there will be also wavelengths pairs, which you can clearly render differently on a monitor, That only depends on where in CIE1931 those pure colors are located, how far they are separated and how large the color depth of your imaging system is. But selling OIII somewhere between violet blue and acid green, depending on who made the image, is somewhat odd.
I am quite sure, this is, what you mean, when saying color is physiological. It looks e.g. violet, but indeed is just a blue and a red emisison peak. The same is for white: it can be synthesized by 3 very narrow peaks, but could as well be a broadband continuum. But that's how our visual apparatus works and has nothing to do with color itself. Coming to Ha or OIII ( whose hue is at least not outside the color triangle, and therefore maybe more intuitive): There is exactly ONE (R;G;B) triple (with R being zero in the case of OIII), that generates a color hue, which is a best fit to the color hue of a pure OIII emitter. It's for sure not perfect - I clearly state in my paper, that narrowband emitters CAN NOT be perfectly represented on any kind of currently available imaging devices - but it is the best approximation for those colors and there is an explicit color tupel for each wavelength and each color gamut. Yes, it is not perfect, as I stated in my paper, but those colors (a) give consistentcy and (b) when displayed on a monitor have the least deviation from the real emitter.
CS
Markus