I have been working on an animation and I have come across a problem. The z pass doesn’t seem to be rendering or at least I am not able to access it in composting, I can look at it after the render by selecting the z buffer but still I can’t save it or use it else where. I have got no idea on how to solve this or why this is happening. I have tried to re-install blender delete the appdata file for blender but still no success.
Pleas help me
Try running the z output through the ‘Normalize’ node.
Z pass is already normalized in the Compositor…
Just plug a viewer node and you should see it as a black and white image in the backdrop. If you have no Z output socket on the Render Layer node, check at the bottom the Layers tab of the Rendering panel. You must have deactivated it.
To save it, altho I can’t imagine a use for it, you need a recent version from the Buildbot ( http://builder.blender.org/download/ ) which allows you to see and save the view of the current viewer node from the UV/Image Editor.
Maybe it’s supposed to be, but a few months back was doing the ‘underwater’ tut and could not get a haze look until I ran Z pass through a normalize node. Maybe it was a bug and it fixed now.
Thx, I put the z pass in to the normalize node and it fixed my problem , so I no longer just get a plane white z pass 
Thx again
The Z depth is not normalised when you render
To save it, altho I can’t imagine a use for it, you need a recent version from the Buildbot ( http://builder.blender.org/download/ ) which allows you to see and save the view of the current viewer node from the UV/Image Editor.
You’ve been able to save the output from a viewer node for years by using the uv/image editor window, even in the blender 2.4x era
I stand corrected about the Z pass… That’s why you usually need a Map Value node or else your Z pass appears all white.
As for saving the output of a viewer, seriously, I’ve never seen the option in my entire life with Blender since 2.48… except a few days ago. In the compositor, I use the backdrop and I use the UV/Image editor only to save the final render. It’s easy to miss this little option… apparently.