It is very useful reading and seeing thoughtful opinions on this, as I know people who buy Blu-ray often 'sit on the fence' regarding older titles and upgrading to 4K at home. I'm told the color gamut is improved, but again wonder if this actually translates to a significant gain in projection.
I've seen the new 2K Blu-ray, but not the 4K UHD. The increase in resolution on the Blu-ray is immediately noticeable, it is a significant improvement over any previous versions I’ve seen. I would imagine the 4K would enhance these details even further, subtle though that may be with older...
The increase in resolution is apparent from the opening of Seventh Victim, seeing (studio) trees jiggling about behind the large stained glass windows. And though that film is softer overall that the razor sharp Zombie, it is a huge improvement over anything I'm seen on this title before.