Hello, i am in the last part of the blenderguru-tutorial. I want to use compositing in order to change the final image. The problem is backdrop won´t let the image appear in the background of the node-editor. The only hint i have is as follows: in the video it appears that andrew used "Last: Link Nodes". I don´t know what that exactly means...
You will need to ⇧ Shift + A add a Viewer node and connect your Image or Render Layer node to the Viewer as well as your Composite.
At the header, tick the option for Backdrop like you have, and the image should show up in the background of the node editor.
1$\begingroup$ thank it kinda worked, but the image in the background is way too big now. How can i scale it down? ...oh i found it: i can zoom out at "Zoom" $\endgroup$ Jan 16, 2017 at 19:18
$\begingroup$ You can use <kbd>V</kbd> and <kbd>Alt</kbd>+<kbd>V</kbd>, also for zooming, and <kbd>Ctrl</kbd>+<kbd>Shift</kbd> left click on a node to watch his output. $\endgroup$ Jan 16, 2017 at 21:02
$\begingroup$ Is it possible to display the backdrop with the viewr and the composite node inside a node group? outside the node group is only the render reult node. $\endgroup$– DanielMay 9 at 14:02
$\begingroup$ No, not as I am aware of. The Viewer node is what is displayed only, and the Final Composite node is the way the full render gets output. The ability to only show a certain group would need a duplicate viewer node so that you can select which one shows in the backdrop. $\endgroup$ May 10 at 15:09
The answer is that you will have to press (shift A) go to output, then pick viewer, after that just connect the yellow image wire to the viewer and there you go. if you press v it will shrink the backdrop image or if you press alt v it will enlarge the backdrop. This answer works in v2.79 so far and may update answer if it changes in the future