user23732: I have a multicam setup mixed with 1080p cameras and 2160p cameras (So I can zoom in on them)
But when I import the 4k clips into my 1080p sequence, they are "zoomed in 200%".
Is there a way to automatically set UHD clips to 50% size on import?

user24155: You can achieve this by the using Default Media Scaling preference, which takes effect when you subsequently import media and/or add to the timeline.
Edit > Preferences > Media > Default Media Scaling and choose "None", "Scale to Frame size" or "Set to Frame size"
Scale to Frame size: Will resize the media clip virtually at import - such that when added to the timeline at 100% it fits the frame.
Set to Frame size: Will set the media scaling dynamically using the effects control, such that at 50% (in your example) it fits the frame. Importantly - you can then rescale the media up on the timeline without loosing the original quality.
You can also use Clip > Video Options > Scale/Set ... (with clips selected in the Media Library or Timeline) to rescale clips in the manner stated above. 


23732: <p>I have a multicam setup mixed with 1080p cameras and 2160p cameras (So I can zoom in on them)</p>

<p>But when I import the 4k clips into my 1080p sequence, they are "zoomed in 200%".
Is there a way to automatically set UHD clips to 50% size on import?</p>
 24155: <p>You can achieve this by the using Default Media Scaling preference, which takes effect when you subsequently import media and/or add to the timeline.</p>

<p><strong>Edit</strong> > <strong>Preferences</strong> > <strong>Media</strong> > <strong>Default Media Scaling</strong> and choose "None", "Scale to Frame size" or "Set to Frame size"</p>

<p><strong>Scale to Frame size</strong>: Will resize the media clip <em>virtually</em> at import - such that when added to the timeline at 100% it fits the frame.</p>

<p><strong>Set to Frame size</strong>: Will set the media scaling dynamically using the effects control, such that at 50% (in your example) it fits the frame. Importantly - you can then rescale the media up on the timeline without loosing the original quality.</p>

<p>You can also use Clip > Video Options > Scale/Set ... (with clips selected in the Media Library or Timeline) to rescale clips in the manner stated above. </p>

<p><a href="https://i.stack.imgur.com/EWVtO.gif" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/EWVtO.gif" alt="Set Import Scaling"></a></p>
