If you create an image of a human face at actual size, in both HD and 4k, the level of detail between the shots will be identical.
Canon 50mm f1.4 lens shot at f4
400ASA | 4500k | 25fps
Cameras: BMCC vs BMPC4k
Sensor Sizes: Micro Four Thirds vs Super 35
Resolution: 1080p vs 2.4k vs 4k
Camera distance from subject relative to resolution: in order be able to make a 1:1 comparison, we need to alter the camera distance so the subject is the same size and we end up with the same composition. Since 4k (UHD, actually) is twice the size of 1080p, we shoot from twice as far away.
4k will be more detailed than everything else because it's higher resolution. The picture is bigger.
2.4k will be less detailed, but better than HD.
The Production camera will probably create more detailed images than the Cinema camera because it has a larger sensor, and because it's 4k - double the dimensions of HD and 4 times the area.
I can know things rationally - and I can know things emotionally. And I can have a fuller understanding of things if I interact with them over time. Nonetheless, experience is often tainted by purely emotional assumptions. I did not get the results I expected. My emotional assumptions that told me 4k was better were so thoroughly trashed I went into a rage over it. I've had a marketers notion of what 4k is, even after working with it. The *only* thing that makes 4k seem sharper, more detailed, higher resolution, is *display* resolution. 4k is good for lots of things, but in terms of detail, if you are viewing in HD, it's more of a liability than a benefit.
More here: Resolution is resolution.
I don't know what the proper technical term for what I'm comparing is. I'm using the word DETAIL in a very common sense sort of way that anyone can understand: how true the rendering of the image is to the object in front of the camera. Can you make out fine details? Can you read Gandhi's name? Is it sharp? Acutance? Resolving power?
Búsqueda exploratoria #006 - Noce à Lens, by Circus Marcus
In the updated version, the only thing changed was the final comparison between HD and 4k from the same distance. Originally the 4k was *fit* on a 1080p timeline, then magnified. In this new version, the 4k is left actual size on the 1080p timeline, before magnification, which is not 400% of 4k, it's 400% of 1080p. In the old version, the 4k *really* is magnified 2 times. In the new version, the 4k *really* is magnified 4 times, ie. it's actual size.
Images were not sharpened or colour corrected beyond:
BMCC HD vs 2.4k Raw - 6% increase in contrast to match shots; raw converted in Resolve without adjustments
BMPCC HD vs 4k - colour temp adjusted to match as I reshot the 4k because I thought the first shot must not have been focussed well enough. There was very little difference in sharpness, but the lights had changed temperature.
Camera distance from subject relative to resolution:
HD = 129cm = 4.23ft
2.4k = 161cm = 5.28ft
4k = 258cm = 8.46ft
Cows graphic nicked from Teds Tees
4k has lots of advantages. I know this. I'm not trying to trash the format, but to note it's a different format - and what I emotionally feel is the big difference, seems not to be the big difference. 4k gives you incredible flexibility and new options when it comes to editing. You can reframe shots. You can crop in, effectively doubling your lens length. Stabilisation works better. Tracking works better. You can pan and scan shots. 4k is the future. 4k is to HD as HD is to SD. And when Vimeo is 4k and when Apple makes 4k iMacs and people have 4k TVs, it's going to be amazing.