Defocus Node help

I was wondering if the defocus node can work on an image after its rendered .what i mean is I tried to render out to a exr file . it works if i use the defocus node in the compositor before i render but if i render the file, save it as a exr file and put the z buffer into the node like normal it dosent do anything…

Defocus and all other nodes work solely on pre-rendered files. This means that you didn’t save your image with any z-buffer information. Go to the format tab and enable the button labeled “Zbuf”, re-render the file and save. Import the image and all will work as advertized.

thanks . i didn’t see that i before