Clips resize (shrink) on adding Fusion composition

Does anyone know why a clip resizes (shrinks) the instant I enter the Fusion tab (and thus create a Fusion composition on the clip)?

Steps to reproduce:

1. Select any clip in the timeline (edit tab).
2. Click on Fusion tab (thus creating a fusion comp on selected clip).
3. Observe how the clip does not occupy the full canvas in Fusion viewport.
4. Return to timeline (Edit tab). Observe how the selected clip is now shrunk in the edit viewport.
5. Right click clip and select "Reset Fusion Comp" from the context menu.
6. Observe how the clip returns to normal size.

I've experienced this behaviour since Fusion was first integrated in Resolve 15. I usually start my Fusion node trees with a transform to scale up the input, but this seems like a sloppy workaround.

Does anyone know why this is happening?

What is the resolution of the clips you are having the issue with?

I've experienced this issue with footage and projects of all sizes.
Currently I'm working on a project with 7k and 5k footage.

Try opening Project Settings, going to Image Scaling>Input Scaling and set it to Center Crop No Resizing and see if that helps.

Hi and thank you for this suggestion! I had never tried fiddling with the Input Scaling settings.

When I set it to Centre Crop, it does indeed stop resizing the timeline clip when round-tripping through Fusion. However, all clips are now heavily cropped in timeline so it seems to work this way I would need to change my Timeline/working resolution to match the footage (undesireable as 7k is heavy and it's not my delivery format anyways).

But this has helped uncover what's going on here:

1. Hi rez clips are imported and downscaled to fit the timeline resolution.
2. Fusion imports the clip pre-scaled at timeline resolution, but placed in a full-sized canvas (as per clip metadata), so clip appears small in canvas with large black margins.
3. Resolve Timeline reads back in the full-sized canvas from Fusion and thus resizes again to the timeline resolution, hence a double-shrunk clip.

So the best solution would be to have Fusion import the original, un-resized/un-stretched media, rather than the resized timeline version.

Any insight into how this might be possible?
Thx!

One (sloppy) workaround would be to change the per-clip Input Scaling setting individually for each clip that will have Fusion work applied, and always be sure to add a Resize node (manually set to project setting) at the end of each Fusion graph.

However, this is not ideal as one can, for example, no longer change the project resolution without having to dive into each and every Fusion comp to manually adjust.

EDIT: Bizarrely, even this workaround doesn't work. Fusion sill imports media scaled to Timeline resolution but within a full-rez canvas, even when that particular clip's Scaling settings are set to crop. It seems Fusion only respects the Project defaults.

EDIT 2: "Fusion>Fusion Settings>Frame Format" settings have no effect (appears to set defaults only).

There are, weirdly, several new posts about Fusion resizing. I hadn't noticed it until now. Not sure if this was an issue prior to 18.1?? In my case, grouping 4k clips into a Fusion clip turns them into 1080 which is not desirable.

UPDATE: I found a solution to my issue which may or may not be the solution to your issue. I'd though I'd set everything to 4k but there was 1 1080 setting in the cog wheel menu. Apparently that's what Fusion uses as its size reference. There are a lot of places that the resolution needs to be set. Great for flexibility I suppose.

Maybe I misunderstood, but the new fusion comp normally is the same resolution as your timeline and imported clips get scaled accordingly?
I use the legacy loaders to import my image sequences into fusion to keep things consistent.

So what happens is the Fusion comp is the resolution of the source clip (which is larger than the timeline resolution), however the clip is imported into the comp at the timeline resolution (i.e. pre-scaled-down) such that it does not fill the entire Fusion canvas. There are empty pixels around the 1080-scaled image out to the perimeter of the full res (8k) composition.
Then when going back to the timeline, the whole comp is shrunk back down to 1080 to fit the timeline, resulting in a now much smaller clip surrounded by a fat black border. This occurs without any work done in Fusion at all. It's the result of simply creating the comp.

UPDATE: I've discovered this bug only occurs in free Resolve. Switching to Resolve studio kills this bug and everything behaves as expected, with no wonky re-scaling.
Therefore the bug is caused by the fact that the Edit Timeline in Resolve free is max-resolution locked, while Fusion is not. Hence the mis-match and the weird compensation between the two modules. My recommendation: Upgrade to Resolve Studio when working with high-resolution source.

Or scale your media in Fusion according to the restricted resolution of your free software.