@rube: Thanks, I actually tried that, but photoshop (CS5 atleast) seems to do that based only per channel basis, I tried setting up a Macro so that it will do math (subtract) from each channel, and then copies them all in another tab and pastes them in the channels, but I couldn't get it working.
On the other hand, a simple subtract from layers will totally make the object look inverted in color, as opposed to the site math, which gives it a more 'relaxed' hue. Mine currently look's completely 100% dialectic, which doesn't look the same in the site.
@EQ: Haha, thanks, but I kinda did already post and look up in that thread, problem is, the only 'reference' image is that of "Emily", and even then the math behind how to get Spec only is not explained.
The link I posted up has a HLSL method of 'retrieving' the Spec and the 'correct' color, but I don't know how it would be compiled or be made into an Action or PS.
Here is the text I'm referencing to:
If the first image is image A and the second is image B, the diffuse image is 2*A and the specular image is B-A. Of course, these images are stored with the sRGB profile. So here is the shader code to compare the two images and separate them out, and store the result as an sRGB image. As always, this code is not actually tested.