BUG: adding a shape mask to an effect on a non-square pixel aspect (anamorphic) clip causes incorrect shape and unintended cropping
- Create a 1920x1080 square pixel aspect sequence
- To the sequence, add a 1440x1080 anamorphic source clip (ie one with a 1.33 pixel aspect ratio) ... image will correctly fill the frame
- To the clip instance, add an effect eg Lumetri, Gaussian Blur etc ... effect is applied to the full frame image.
- To the effect instance, add a shape mask.
Expected result : effect is constrained to the area defined by the shape.
Actual result: effect is constrained to the area defined by the shape, but that shape is incorrectly squeezed to the sequence's pixel aspect ratio ie 1.333 PAR shape is squeezed by 1/1.333 to become a 1.0 PAR shape, meanwhile all areas of the sequence's source image instance lying outside the effect key's frame buffer are lost ie the full frame 1920 (ie aspect adjusted) image in the sequence, becomes a 1440 (aspect adjusted) image crop.
Basically, it seems like the effect key's image buffer is being created anamorphically (ie per the source) but is being applied as if its square (per the sequence) and everything outside the image buffer's boundary / window is lost.
Workaround is to nest, or use an Adjustment Layer, to apply effects.
Issue has been observed recently across multiple Mac based systems running OS X Catalina and Big Sur.
Alan Govenar commented
Same problem. I took the footage over to After Effects and rendered it there.
Same problem here.
In the wait of a bug fix, a temporary solution is to put the shot alone in a sequence #2 which has the same settings of the sequence #1 in which you edit, then to drag-drop this sequence #2 into your sequence #1 (like you would import a shot - it will appear green) : the effects you put on this sequence-shot won't change its ratio anymore.