I am experiment the cicles material nodes.
I am trying to do a punched sheet metal, and i already no how to make transparent, but cycles don make the shadows correctly …
if someone can help help me… sory if double post… but i searched and no help …
Never use ADD closure, only Mix. Same for multiply with one of arguments > 1. Reason is you broke render GI equation and ADD light energy without notifying internal algorithm (use emission/background for that).
In your example, you have output alpha always > 1 (opaque) because of Diffuse BSDF(R, G, B, 1) + Transparent (R, G, B, T) = Output (R, G, B, 1+T)
Maybe it is good idea to put warning when someone use Add closure at color route.
Edit:
In your case you need to multiply, but you can try to use Mix Frac input as transparent texture, use Diffuse BSFD as one mix color and Transparent as other.
i there the anser is to pro … thanks i will try out what i can understand … D:
Do you now were i can find some information on node maping for cicles
??
I went ahead and started looking at a node setup that might work for you. I’ll explain it on a node by node basis.
The node editor image:
Node A: Material Output. Self explanatory.
Node B: Mix Closure. It takes two other material closure nodes, and sends the results to the output. The Fac value defines how much weight each closure gets.
Node C: Image texture. The image I set to this texture was a black-and-white checkerboard. When attached to the Fac input on Node B, it will serve as a mask for the Mix Closure.
Node E: Diffuse Closure. Adds color to one of the inputs on mix.
Node F: Transparent Closure. Adds transparency.
Node G: Another Image texture. It’s one of my previous renders. This one is attached to Node E, to make the non-transparent Diffuse pieces of the plane more interesting.
The image resulting from rendering. You can download the .blend below. Have fun. 
Attachments
Cycles-Alpha-Mask-material.blend (1.51 MB)
You are the bosss… thanks allot … that’s why I love open-source … 
thanks … i will show you the final results …