Yes, I think you've got the right idea about the tool. It removes to transparency the selected colour while "blending" the resulting transparency with what's left of the original image.Alan9940 hat geschrieben:The more I play with CTT I'm starting to understand that it's not really meant as an "Automask replacement" (though I was trying to use it in that manner), but more for removing color from transparent areas of an image; such as a bridal veil against sky, for example.
Consider these scenarios:
Leaves against a sky
The problem is that the edges of the leaves are not usually a sharp, distinct edge. So the CTT not only removes the sky, but also creates a graded transparency for the fuzzy edges that does not leave a halo around the edges. You're right about the colour component being removed wherever it appears -- if Hue of the leaves is distinctly different from the sky colour (such as autumn leaves, or dark green leaves), the resulting transparency of the kept objects (the leaves) is so slight as to be irrelevant. If the leaves are a pale Hue where the selected CTT colour is a significant component of their hue, then the leaves will become noticeably transparent. (The same is true for a colour shift occurring in the leaves.)
Distant mountains against a sky
Another tough case because the atmospheric haze will cause the Hue of the mountains and the Hue of the sky to have a significant amount of the same colour. Here's where it will be absolutely necessary to first create a mask to protect most of the mountains from being affected.
Transparent objects (glassware)
As in the example I referenced earlier, this case is where the CTT does an outstanding job because the glassware does not have any Hue of its own, and is merely passing through the background colours.
ChromaKey backgrounds
The example I referenced shows the benefits of CTT in cases where the subject has been photographed against a background that is significantly different in Hue from the subject. Again, CTT is excellent for this.
I couldn't have said it better!Alan9940 hat geschrieben:I really think it's all going to boil down to that CTT is simply another tool that when combined with other tools will allow you to perform magic!
As a general rule of thumb for the CTT tool, it's probably best to first do a rough mask to protect areas, leaving the edges of the subjects to be affected by CTT.
