I would love an answer to this, too. Does nesting decrease quality of footage?
Nesting, in and of itself, does not affect the quality of the image.
From the info you've provided, I'd wager that quality is being compromised by changing resolution. What is the resolution of your source content, and how exactly are you scaling the nested UHD sequence to lower res sequences. However you're doing it, I expect you'd find exactly the same results if you dropped UHD clips directly into a lower res sequence and scaled it down in the same manner.
thank you, Mark. Also, is there a way to nest that does not clip the image, so that if I want to decrease scale while a nested image plays, I would have image leftover outside the frame for doing that?
I just finished a project with similar requirements. I had to stabilize 6K footage and then edit into 1920x1080.
I did use nesting for the off-line/decision making process, but for the final edit I did export the stabilized 6K (with no crop or auto-scale) and then brought those files back in for the final edit.
The whole process of nesting does crop the image to the nest sequence resolution, so to have the ability to scale without cropping, don't create your nest from within the current (lower resolution) sequence, instead create a full resolution (from original clip) sequence and then drag that sequence into your lower resolution sequence.
thanks, qengineering. I wish I had the experience to understand what you wrote. thanks for writing--i'll have to play around more to understand!
So sorry, I guess my shorthand isn't always clear.
To answer your first question, no, Nesting should not decrease the quality of the footage.
In your second question you say that the nest (nested clips) causes the image to be "clipped" (aka cropped) when you decrease the scale of the nest.
Most of the time you create a nest by highlighting one or more clips in an existing sequence and right-clicking to select Nest..., by default this creates a nest with the same image size as the original sequence. If you scale a nest that is the same image size as the sequence (i.e. 1920 x 1080 nest in a 1920 x 1080 sequence), it will show black edges when scaled smaller than 100%.
To avoid this cropping, your nest must be a larger image size than the sequence you're placing it in. Placing a 3840 x 2160 nest into a 1920 x 1080 sequence will allow you to reduce the scale to 50% before revealing the edges of the nest. A nest is simply an independent sequence placed inside another sequence. To get an independent sequence that is a different image size than the sequence you're working on, you can drag a higher resolution file to the New Item icon, or right-click on the higher resolution file, and select New Sequence From Clip (let's name it 'Nest 1'). Build and modify Nest 1 as desired and when ready, drag the Nest 1 icon from the Project window into the (original) sequence that you were working on. If necessary, double check to make sure Nest 1 inside your original sequence is not set to Scale to Frame Size by right-clicking on the Nest 1 in the sequence.
I hope this helps a little more.