I'm really surprised by the quality of the visuals in some new movies this year (2018). I'm curious to know in what resolution these cameras typically record to experience this quality on a cinema screen?
When distributed to the theaters, new digital films will likely be 4K, with better color depth and resolution than home 4K. But theaters will not be able to show at that resolution if they have not upgraded their projectors to the latest capabilities.
Also, older movies being shown again will be at a lower resolution than movies released in the last few years, unless they have been remastered.
Here's a Wikipedia except that seems to have been written several years ago:
The theoretical resolution of 35 mm film is greater than that of 2K digital cinema. 2K resolution (2048×1080) is also only slightly greater than that of consumer based 1080p HD (1920x1080). However, since digital post-production techniques became the standard in the early 2000s, the majority of movies, whether photographed digitally or on 35 mm film, have been mastered and edited at the 2K resolution. Moreover, 4K post production is becoming more common (Dec 2013). As projectors are replaced with 4K models the difference in resolution between digital and 35 mm film is somewhat reduced. Digital cinema servers utilize far greater bandwidth over domestic "HD", allowing for a difference in quality (e.g., Blu-ray colour encoding 4:2:0 48Mbit/s MAX datarate, DCI D-Cinema 4:4:4 250Mbit/s 2D/3D, 500Mbit/s HFR3D). Each pixel has greater detail per frame.
According to this page (from 2017):
...most major cinemas in the UK and a lot in the US will now use 4K digital projectors, and will have been doing so for several years.
The page also claims that the first movie to be shot in 8K resolution is Guardians of the Galaxy, Vol. 2, so it won't be possible to see movies shot digitally prior to that in any resolution higher than 4K. One advantage of shooting on film is that film could be re-digitized at higher resolutions when they become available.
And regarding comparison to analog film print projection:
For comparison purposes, 70mm film - still considered by many to be the gold standard - is roughly equivalent to a 12K resolution in digital terms, so digital's still got some catching up to do on that score.
I will point out that for most of my lifetime prior to the advent of digital projection, 70mm analog projection was pretty rare. I was able to see a 70mm print of Ben Hur in an art house theater in Los Angeles once. It was very impressive. Most movies were projected from 35mm prints.
I did see one of the first North American digitally projected shows ever - the digital remaster of Akira - around 2001. It was mostly impressive, even with a much lower resolution than today, but there was a pixel that got stuck partway through and stayed stuck the rest of the show. The 70mm Ben Hur experience was overall superior.
I'd imagine they would capture in Ultra HD (3840 x 2160) at the very least, though with the recent push to release 4K (4096 x 2160) to the home market I'd suspect many are filming in that resolution.
Don't forget, some (like Quentin Tarantino) still prefer to use actual film, and shoot on 70mm film for best results.
For more info than you'll ever want to know, take a look at this web page about professional film cameras and all that goes in to making your video as good as possible.
Apparent visual quality in a movie is a function of several things coming together. Resolution is part of the story, but it isn't the whole part - or even really a big piece of it.
Digital Production: First, many film producers are using digital production all the way through post-processing. This allows for more rapid assessment as to the general quality of the shot. Of course, it goes without saying that it is easier to tweak the digital video shots for lighting, brightness, contrast, saturation, etc. - which is abhorrent to most cinematographers, but that's the way it is now. This makes it easier for the visuals to "pop." Most of the time this is 4K resolution, but I've heard of even higher used.
Digital Projection: In the cinema, perhaps the biggest hitter in terms of visual quality has been the replacement of film with digital projection technology. I've heard people mutter about film having higher resolution -- hogwash. The human eye is incapable of perceiving pixels from a 2K source in a normal theater screen (25-30 feet wide) at a normal seating distance; thus, resolution has very little to do with the overall quality (in large format, 4K is a must-have due to the enormous screen size). In fact, the vast majority of theaters do not use 4k projection. There is no benefit for the cost in 90% of houses.
What digital projection brought was better technology all around. Whereas film projection used mechanical means to transport and show the picture, digital has no moving parts. The steadiness of the digital image is immediately apparent. Additionally, the light from the xenon lamp had no optical path - it went straight from the reflector through the film, lens, and onto the screen. If the lamp was mis-focused -- as they often were -- you'd have a bright center and dark corners. Digital projectors have an integrator prior to the light processing engine which evens out the light and ensures uniform brightness across the screen. Colors are more accurate because digital projectors are field-calibrated for color temperature by RGB channel. Last, but not least, the digital image is brighter and more pristine than the film because the specification is better enforced than it used to be (and because digital doesn't accumulate dust and dirt).
Bottom Line: The quality of your digital image depends on a lot of things, with resolution being a small, generally negligible part.