Difference between the Mix and AlphaOver node?

I’ve only been using the compositor in Blender for a short time so I’m discovering new things all the time. One of the nodes I always use is the mix node, basicly everything comes together in this node so I’m curious about what the AlphaOver node offers over the Mix node?

What is the actual difference between the color -->Mix node and the color --> AlphaOver node. From my limited experience with the compositor the AlphaOver node is just a Mix node without the blending options. I have noticed some difference with blending alpha channels but thats it.

If anyone could give me an example of when to use the Mix node and when to use the AlphaOver node, in such a way that it is unwise to use one over the other.

Don’t use the mix node as a stand in for alpha over. It requires more work to achieve the same results. Instead use the mix node to control/alter the opacity of other types of mattes that will ultimately be used as an alpha channel. You do this by setting the mix node to “Multiply”, setting the “Fac” to 1.0, plug the matte into the top socket and set the color of the bottom to some uniform level of gray that the matte is to multiply with. The gray color determines the opacity of the matte when plugged into the alpha socket of a “Set Alpha” node. There are many other uses but this is probably the most common.

My problem is actually the opposite, when I use the Mix node or the AlphaOver node I get the same results. The only difference I’ve been able to discover is the Blending options in the mix node and the ConvertPremultiply in AlphaOver node.

I use the mix node when I need the Blending options (add, multiply, etc.) your example is very specific, the mix node can be used more and I actually use it more then the alpha over.

You asked for specifics for when to use one as opposed to the other and you got them. Now you’re complaining because I didn’t give you an exhaustive review of the node’s capabilities?

I don’t struggle with the compositor in any regard but I foresee many hours of sheer frustration in your future.

Mix node has many mixing methods. It mixes to the degree specified by the Fac socket, regardless of the alpha channel. AlphaOver mixes where the alpha channel (transparency) says to. If there is not alpha (transparent) overlap, the Mix on Mix mode and AlphaOver will give the same results.

My point is, what can be done with the AlphaOver node can be done with the mix node. You mentioned that I shouldn’t use the Mix node as a stand in for the AlphaOver node and then you give me an example that doesnt illustrate this. Instead you give me a random example of how the mix node can be used. I already use the mix node, Its the AlphaOver node I never use

Temper, temper.
I was asking for clarification, no need for this.

Thanx, thats all I needed to know.