Addon for Blender to maintain a camera's focal length/distance ratio.
See promotion video here: https://youtu.be/db8TEAO8qDM
See a video explaining how to use it here: https://www.youtube.com/watch?v=6pBx33feU4c&lc=UgyskxmQ_82Gvtjy8gp4AaABAg
Note: if you are experiencing trouble installing the addon, please click > Code > Download ZIP. And then unzip the file. Go to Blender and install the Python file that is in this unzipped directory.