I do all my work in a 1920x1080 sequence and shameless crop and blow up (all the way to 1080x1920) on export as needed. It’s ephemeral media that’s going to live for a few weeks on people’s phones as a hyper-compressed mp4, not a museum installation. Don’t sweat about it unless the piece you’re working on is all graphics with crisp lines and type, in which case you might want to work native.
I make every deliverable at the native size. When I bring in references I size them to 10bit 1080x1080, 1080x1350, or 1080x1920, depending on the delivery requirements. I drop a copy of my 16x9 timeline on top and resize to suit using the native size sources. I don’t ever have to worry about what crops to use on exports, or anything like that. Most title animations I get are re-configured anyway, so I have them rendered to the delivery size if I’m not making them myself. Most of the titles I do, I make at 4k anyway. I got burned when a client got to see a native rez title next to a blown up one, so I stopped doing the blowup.
I agree on making a naitive size but what do you do if you have all of your source material at 1920x1080. Would you do a blowup to 1080x1350 for the 4x5 version?? Or would you leave the vertical Rez at 1080 and lower the Rez on the horizontal. Ie 866x1080.
I would stick with the full rez size and blow up footage if needed. I like to stay consistent. I would still take advantage of the sharper titles even if the footage “suffers,” (What the hell, people just look at this shit on their phones anyway) but I seldom see that size unless its sports stuff from TV. Even most stock I get these days is at UHD.
When I have a job that calls for social deliverables, 90% of the time I master at either UHD or HD depending on the client’s largest ask. Then in my Autodesk Folder Template that I keep on my storage outside flame, I have a TEMPLATES folder that has a .png at every raster size I’ve ever had to deliver. 1920x1080, 1080x1920, 1200x1200, 1080x1080, 1080x1350, 972x250… you get the idea. When I setup the project and drag the folder in, I make sure the import settings are at the desired bit depth and frame rate and they then sit dormant until needed.
At the end of a job when I have to make a certain size they didn’t specify (or know to specify up front), more than likely I’ll have a single frame ready to go that I can open as a sequence and drop the master in. The resize node is automatically applied, and it’s a matter of pan&scan or animate the position of each shot to keep the product legible in the frame.
The size of the 4x5 I’ve always used is 1080x1350, because all of my clients that ask for that ratio specify that size. I know it scales up, and so do they, but it checks the box on their deliverables grid which makes them happy.