Hi Frischvergiftung,
Here are some examples, adjusted in the Material for the ratio. Yes, it is round, but use the timeslider to go to frame 72.
The Scale and Offset in the Texture node need to be set so that it maps each image to a 1:1 starting point. Vignetting is present, so scale down and offset. Just as each camera lens or projector lens, without framing, would create a circle larger than the sensor or film. The numbers relate to the Lower Left Corner of the image. The Offset is then set to -1 to position that corner of the image in the upper right. Hence, only values between make sense.
The Material holds three Texture Nodes; connect them to see the ratio. Use the time slider to adjust the final size.
https://projectfiles.maxon.net/Cineversity_Forum_Support/2025_PROJECTS_DRS/20250821_CV4_2025_drs_25_RSip_01.zip
Screenshot 2025-08-21 at 9.38.00 PM.jpg
You can set presets for the Texture Node; test these carefully with your footage ratios before going into production. The file is just a demo.
All the best