Hi Bob,
Several years ago you said?
The concepts of "true color" and "natural color" are illusions in deep-sky astrophotography. Such things don't exist. The main reason is that a deep-sky image represents objects far beyond the capabilities of the human vision system.
So which is it, you seem to have change your mind.
Not at all. I think exactly the same today: color is purely conventional in astrophotography. The best example of this is narrowband imaging, where one has to use an arbitrary color mapping convention or palette in order to represent different wavelengths outside the RGB band as an RGB image. As long as your rendition is consistent throughout the whole image, any palette is valid, although some palettes will allow you to represent the data better than others. The same is true for RGB data. For example, nothing stops you from exchanging the red and blue components if you have a good reason to do so, either from a purely aesthetic perspective, or for the sake of information representation in a particular case.
For conventional RGB color representations, where the R, G and B components are to be represented as red, green and blue colors respectively, any white reference is applicable for the same reason. This is why we provide a large set of selectable white references in PCC, including most spectral types and a number of galaxy types, among other options. However, the choice of a white reference may have a strong impact on the documentary value of the image in our opinion, and this is a very important point for us. We think that no spectral type?including G2V?is suitable as a white reference because, in general, no particular star is representative of the objects being shown in a deep sky image. On the contrary, the integrated light from a spiral galaxy may provide a combined source of all of the existing spectral types and deep-sky objects, which makes it an excellent neutral, unbiased white reference for RGB deep-sky data. An unbiased reference is essential to generate a rendition that can maximize information representation, which is a crucial goal for us. For this reason, the default white reference in PCC has been generated from the average fluxes of Sb, Sc and Sd galaxies, or what we call the
average spiral galaxy reference.
Then you said in this announcement?
If you want to persist in making common conceptual mistakes, you will be able to use the G2V spectral type as a white reference?but PCC will allow you to select virtually any spectral type, along with several galaxy types, to calibrate the color of your images automatically and accurately in PixInsight.
I find this statement incredibly arrogant. Who are you to say that your color philosophy is better than anyone else's? Also, you are again stating that PCC provides "accurate" color, which you previously stated does not exist. At least one astrophysicist and many of the best astrophotographers on the planet accept the G2V and/or eXcalibrator methods. eXcalibrator's Linear Regression routine uses stars of multiple colors and gets the same result as the "white-star only" routines.
Sorry if that sounds arrogant to you, but it's just a concise description of what I think. If you prefer, I can prepend an IMHO token to say
IMHO, using the G2V spectral type as a white reference for deep-sky images is a common conceptual mistake, or even polish it to say
IMHO, using the G2V spectral type as a white reference for deep-sky images is not the best choice, but I am not a big fan of palliative formalisms. In part this is probably because my mother tongue is Spanish. We tend to say things more directly and less sweetened in Spanish. At any rate, my intention has not been to put myself above anybody.
As for the rest of your post, I prefer to not comment more on that.
