I have a Mac Pro 5,1* with an Nvidia Quadro K1200 graphics card. Note that while this card is not officially supported by Apple, it works perfectly with Nvidia's graphics driver. The K1200 powers two Dell P2415Q 4k monitors (4k@60Hz). I am very happy with the monitors, as the 4k is a massive improvement over the 1080p monitor I was using before.
However, my computer would beg to differ. For some reason, MacOS has decided not to recognize the screens as 4k. All of the System Preferences, System Report, and other display information insists the screens are 1080p60.
Photoshop recognizes the screens as 4k (for example, when a 24MP image opens full screen, the zoom is ~40% (on a 1080p screen, it would be ~15%). When I take a screenshot that is 2px wide and 4px tall (as recognized by the system), I can count 4px across, and 8px vertically.
More information: I am running MacOS Sierra 10.12.2 build 16C67. This discrepancy is on the "default" resolution scaling. I can choose other scaled resolutions, but only up to 3360x1890, which is significantly smaller than the official 3840x2160 the screen supports (which I appear to be getting).
My question: why does this discrepancy exist?
*Note: the computer is actually a 2009 model (4,1) but has the (5,1) firmware upgrade.
This is the output of
Graphics/Displays: NVIDIA Quadro K1200: Chipset Model: NVIDIA Quadro K1200 Type: GPU Bus: PCIe Slot: Slot-2 PCIe Lane Width: x16 VRAM (Total): 4095 MB Vendor: NVIDIA (0x10de) Device ID: 0x13bc Revision ID: 0x00a2 ROM Revision: VBIOS 82.07.7f.00.14 Metal: Supported Displays: DELL P2415Q: Resolution: 1920 x 1080 @ 60Hz (1080p) Pixel Depth: 32-Bit Color (ARGB8888) Display Serial Number: Main Display: Yes Mirror: Off Online: Yes Rotation: Supported Adapter Type: DisplayPort Automatically Adjust Brightness: No Television: Yes DELL P2415Q: Resolution: 1920 x 1080 @ 60Hz (1080p) Pixel Depth: 32-Bit Color (ARGB8888) Display Serial Number: Mirror: Off Online: Yes Rotation: Supported Adapter Type: DisplayPort Automatically Adjust Brightness: No Television: Yes