I’m curious why you would upscale the Blu-Rays instead of simply using the existing 4K transfer that’s already on disc. Seems like you’re just making more work for yourself that way.
The answer is simple : the final original masters for Episode I - II - III will always be 1080p. And everything released from that point that is and considered “superior” to the 1080p versions will always be an upscale. Even the officially released 4K masters. I would have avoided a step for my 4K Filmized Remaster by using the 4K masters, for sure, but I think Disney did a pretty bad job with their upscaling method (on Episode I, at least).
Here is a quick and bad example of their process : wide shots almost always looks over-sharpened on the official 4K master, while my 4K Filmized Remaster off the 1080p master looks much more natural. See the screenshot below :
4K Ultra HD image
4K Filmized Remaster (off 1080p source)
4K Ultra HD image
4K Filmized Remaster (off 1080p source)
