Kent had asked me about my use of calculations with masks in another thread. I thought it might be of more use to start a new thread on the subject of calculations.

Some will find this stuff kinda like a sleeping pill, you'll nod off during the second sentence. To those I say...you don't absolutely need calculations, it's not necessary knowledge, it just makes life easier for the hard-core PS'er. Class dismissed.

OK, the two of you that are left can wade through this with me :)

Sometimes you have a subject that you need to mask that contains both light and dark areas. It's easy to construct a mask for the lighter portion or the darker, but difficult to do both in the same mask.

Here's an example. This was originally a photo, but the tones remain the same in this rendition. The little girl's hair is dark and her clothes are light:

http://www.pbase.com/image/11780422.jpg

Creating a channel mask for the hair resulted in this:
http://www.pbase.com/image/16788845.jpg

And the mask for the clothes:
http://www.pbase.com/image/16788846.jpg

After running calculations, choosing the mask channels with blending set to "Add" gives you a merged copy:
http://www.pbase.com/image/16788848.jpg

There may be an easier way to achieve the same result, but I haven't found it yet.


--
Pam
http://www.pbase.com/pam_r
'art is working on something 'til you like it...then leaving it that way'