HFS+ and exFAT
Like its smaller cousins, the Production Camera has no option to format disks in camera, although that's an option I would see as dangerous in most sensible workflows anyway. The camera supports both HFS+ and exFAT, and the choice is between a more modern and reliable journaled filesystem or the universal compatibility of exFAT. Anyone wishing to record 4K raw will need to invest in speedy storage – perhaps Intel's recently announced “enthusiast grade” 730 series which are individually tweaked for uprated speed capability at the factory. The camera will accommodate either 9.5mm or 7mm thick SSDs, although 7mm types will flop around noisily inside the SSD bay, potentially stressing the SATA connector, unless the plastic spacer supplied with many low profile SSDs is used. Playback is straightforward, including downsampled playback via 3Gbps SDI of 4K clips, although the camera will only play back files recorded at the frame rate to which the camera is currently set. Since there is no list of files, just a “next” and “previous” button, this can lead to the stomach-churning suspicion that the SSD is for some reason suddenly empty; panic not, just select an appropriate frame rate and try again. It's worth noting that the display strip at the bottom of the image always displays the current camera settings, not the settings at which the currently-visible clip was shot.
Pictures, then. It is, of course, very sharp, and potential owners will need to be careful that lenses they intend to use with this (or any other 4K) camera aren't going to let the side down. The difference between the supplied Sigma 24-105 f4 zoom and a less costly Tamron 28-300 f3.5-6.3 was visible all the way down to f8 in a way that isn't so obvious on 1080p cameras. This is especially true for people upgrading from things like the Canon EOS 5D Mk. II, which were never capable of filling even a 1920x1080 image with accurate information; lenses that looked fine there may embarrass a 4K production.
So far, so predictable; the hunger for resolution of modern sensors, even in DSLR stills work with APS-C chips of ten-plus megapixels, is well known. The flipside of cramming all those pixels onto a super35 sensor, especially with the extra circuitry for global shuttering, is that each pixel is necessarily smaller and therefore less sensitive, or more noisy, which is nearly the same thing. That effect is certainly visible in comparison to the 2.5K camera, even given that camera's smaller sensor. The native sensitivity is at best ISO 400, perhaps even then best overexposed half a stop, with the 800 option suitable for emergencies only. The hike in noisefloor almost directly implies a reduction in dynamic range, too, although a quickly improvised dynamic range chart indicated at least twelve stops. The sensor performance, more than anything, is the major sign of economy on this camera, but anyone willing to do the mathematics will realise that while it might be a quarter the speed of an F65, it's also about a thirtieth the cost, and that's more than fair.