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Good detail in the nebula, but star
colors are largely lost. What happened?
Good detail and good star color.
How can we achieve this?
Layering a fully-black to fully-white
luminance layer on a correct star color results in desaturation of the color
at the white end.
Same thing happens for a star of a
different color. The result: all stars look white.
One possible solution.
Note the loss of contrast as luminance
opacity is reduced.
The clipped stellar profile in the M1
image allows only a very small ring of the star image to display color. The
more rounded profile in the M13 image allows more of the “body” of the star to
take on color.
First select “auto” for both background
and mid-level. Then uncheck the “auto” boxes and set the parameters to desired
values, usually a bit lower on both.
Disable sharpening by setting the user
filter to a “1” in the center and zeroes in the rest of the boxes.
Undo, change the background and/or
mid-level parameters, and re-apply DDP as many times as need to 1) avoid
clipping, and 2) get the desired contrast in the image.
Mismatch in luminance vs. color data
causes a distortion of the color. Bright stars are overly saturated, while dim
stars have lost color altogether.
Applying DDP to the color data keeps it
matched with the luminance data.
DDP stretching the color data does tend
to desaturate the color a bit (as is the case with any dim-to-bright