Exactly match orthographic camera to object so it fills frame?

Hi folks,

Imagine this:

I’m doing some compositing in DaVinci Fusion.

I want to bring an image sequence into Blender to do some specific effect (like Eevee bloom).

So i export my 1920x1080 sequence, bring it into Blender by loading it as an “image as planes”.

Now, i set up an orthographic camera and, by some pixel peeping, i discover that i need to set the orthographic scale to 1.778 in order to exactly fill my frame with my 1920x1080 image.

My question is: is this the best way to do it, or is there some more automatic way to precisely zoom the camera to the object so i get an exactly matching scale when i export and bring my render back into fusion?

I know i could also do this by bringing my image sequence into the compositer, but i want to do it in the viewport as that give me more possibilities and realtime.

Clear as mud I’m sure!

Anyone have any ideas on this?

Thanks!

From playing around a little withe the orthographic camera, it seems that, with an orthographic scale of 1.0, the longer side of the camera window (depends on the set resolution) is always 1.0 long.

This means, that if the image sequence loaded as a plane is 1.0 wide and 1080/1920 tall (just the dimension of the plane), then an orthographic scale of 1 should fit the plane exactly.

AHA! … and if we divide 1920 by 1080, we get 1.778, the magic number from my previous post!