Bev, my software (GIMP) has very limited Lab colorspace
capabilities. In fact the only capability it has is
to "decompose" an image into L, a, and b channels. It
does so by creating three greyscale images, one for
each channel. (It can also do this for RGB, and CMYK)
I guess I should've mentioned that. I have no experience
with Photoshop (won't run on Linux), so I pressumed the
same thing was done in PS. I guess what this means, in
effect, is that I was working with a greyscale image
composed of just the yellow and blue values from the color
original. Hmmm... I just started tinkering with it, so I'll
have to do some more reading on it.