I’m very new to Natron, so my apologies first up for what is probably a basic question.
When I create a new project, I set the project settings size.
In the viewer window, I can see white box that represents the dimensions of my project.
Once I “read” an image, this project dimensions box disappears and I have no way of knowing if my sequence will be within bounding area of my project when I go to write it.
So my question is, how I can I see the project dimensions when using the viewer?
I think I worked out a way to display the project dimension bounding box by adding a merge and a checker board.
If there is a better way of doing it. Please let me know 
You’ve got the right idea. You merge it over something is the size you want to work at, usually footage. You can also use a reformat node if you want to composite at 4K but then output at 2K for example.
Its always the first footage you import that makes the calls on output resolution. Even though I set the project format to 1080HD, the Output Format is changed when I import a footage that doesn’t match the output resolution.
ALSO. When you merge, the B-side of the merge makes the calls. It doesn’t change render resolution. Only Viewer resolution.
IF you have a 4K footage on the B-side merge anywhere, it doesn’t mean the output will get rendered in 4K. The output will be in whatever resolution is set in the Output Format.
More on this in this video (actually I recommend watching the entire playlist):
