You misunderstand
's intentions.
As
@Meta4 has stated, a tiff file from a 3840×2160 video screen grab will never be better than a dedicated still DNG shot at 5472 × 3648 with an appropriate shutter speed at the identical moment. With your prior still photography background and experience, I am surprised that you would continue to argue that it could be. That's like saying a .JPG is better than a DNG. You have thrown away more than half of the sensor information before you even get started with post processing. The ideal shutter speed for a cinematic video is the reciprocal of twice the frame rate, designed to
get motion blur. The ideal shutter speed for an aerial still is as fast as you can get it, to
minimize motion blur. The resolution is significantly smaller on a 3840 x 2160 video screen grab than a 5472 x 3648 DNG. Just multiply out the pixels. 8MB vs. 20MB. Capturing the screen grab as a larger lossless TIFF file doesn't create any improvement in resolution. It just means less loss while manipulating the file later in post processing. Your 4K video recording is not raw video. It is highly compressed using the H.264 compression algorithm. A 20MB still DNG recorded by the drone camera is a true raw file with the fullest dynamic range.
As
@Meta4 has stated, you are doing the best you can from your 4K video, but it will never be as good as a DNG still, properly recorded at a high shutter speed by the camera at the same moment, which
is "Photography at Its Best" instead of using a sceen grab from a 4K video recording.
All that being said, shooting continuous video in 4K gives you far more images to choose from, in the individual video frames, than the still camera settings allow in frames per second to capture that decisive moment. 30 fps at 4K provides both stellar video and great screen grabs that can be printed up to 16x20 or larger, as long as you don't stand too close to the print!
However, a DNG still image could potentially be used for a billboard, while any screen capture from the 4K video will fall apart at that size.