Since we're dealing with beginner node tips here are a couple more.

A mask effect is convenient when white means on and zero means off. What if you need the opposite? What if you need white means off and zero means on? Do not make a reversed mask in Photoshop and load that. Instead, take the original mask and calculate the complement, or negative image.

Subtract the map from 1. This will make its complement or negative image.

If the original map node is called M, I'm saying you want:

1 - M

Now it should be obvious how to do this, right?

Math node

Mode subtract

Value_1 = 1

Value_2 = 1

Value_2 connected to M

How about if we want a grayscale version (so as to have a single number) of a color map?

Just connect it to any math parameter value and it will be converted to grayscale.

What if we want to multiply a color map with a number, perhaps to make it lighter or darker?

Add an HSV node. Set the color to white, and connect the color parameter to whatever you're trying to change the brightness of. Then set how bright in the Value parameter. That parameter is multiplied with the color parameter and what is plugged into the color parameter. It is a 3-element multiplication.

 

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