Adobe Premiere Pro is a leading application for composing videos. But, those familiarizing themselves with this application will undoubtedly get frustrated at the fact that it does not allow changes to resolution/dimensions (or just about any other settings) of a sequence once created. However, you can create another sequence with the settings you need and then copy and paste everything, including A/V clips, timing, key frames, and effects, from one to the other through the timeline panel.
After creating a second sequence with the correct settings, the timeline will have a separate tab for each sequence. Follow the instructions below to copy your work from the old sequence to the new one.
- Select the old timeline tab (the sequence with all your work).
- Select everything in the timeline (Ctrl+A for PC, Cmd+A for Mac).
- Copy the selection (Ctrl+C for PC, Cmd+C for Mac).
- Select the new timeline tab (the empty target sequence).
- Paste the copied selection (Ctrl+V for PC, Cmd+V for Mac).
You may have to adjust size and position of any clips that are not set for “Scale to Frame Size” and any that have motion effects. But, at least to don’t have to waste your time completely rebuilding a sequence from scratch.
David's Technical Blog 