Mix Node vs. Math Node

What are the differences [in function or output results] between doing Add, Subtract, Multiply and Divide operations using a MATH node vs. a MIX node?

Is this just overlapping functionality between the two node types? Or [for example] is the Math Node > Add operation different from the Mix Node > Add operation?

I read through the Wiki manual entries:

http://wiki.blender.org/index.php/Manual/Compositing_Nodes_Convertors#Math_Node

http://wiki.blender.org/index.php/Manual/Compositing_Nodes_Color#Mix_Node

…but I’m still not sure about the answer to my question.

Mix nodes are for blending RGB images. Math nodes are for working with single values, like an Alpha or Z value. The Mix nodes are specifically set up to work with all three values in the RGB channel, where as the Math nodes operate on only the first one, if there are more than one coming into the input socket.

Also, notice the different modes of the math node: Logarithm, Round, Cosine, etc. These are clearly for doing, well… math. The mix node modes are what you typically find for image blending somewhere like Photoshop: Darken, Screen, etc. Yes, there is some duplication of terminology like Multiply, Add, Subtract, but don’t let that fool you!

I’m reading through a couple books on compositing. There is a “Maximum” blending operation [and the opposite: Minimum]. What is the equivalent mode in Blender’s Mix node? [One book mentions that Photoshop uses the term “Lighten” for this blend mode. Is it the same for Blender?]

Yup. Maximum would be “Lighten” and Minimum would be “Darken”. Although in PS, the term “Maximum” and “Minimum” usually refer to filters which have a completely different function, not mixing methods.

Hmmm…well, I thought that the book was referring to layer mix modes; but in any case - as long as I know how to transfer the info in the book to Blender so I can start practicing, then all is well.

Thanks for your help.