Running a 3840 pixel display on a 2013 Mac Pro. When the display is set to default, Lightroom reads the display resolution correctly in the Catalog Setting/File Handling/Standard Preview size/Auto setting. Lightroom shows 3840 and in "about this mac" the Graphics/Displays Hardware readout shows a resolution of 3840 also.
However if you choose a scaled setting for the monitor, such as 3008 pixels, this shows properly in the hardware readout, but shows as being 6016 pixels (Double the actual resolution) in the Lightroom 6 readout under the Catalog Auto Setting. This causes problems with the zoom functions. You can't zoom in to actual 1-1 pixels when set at this resolution. Plug-ins in Lightroom handle the resolution correctly as does Photoshop. Couldn't see the readout in Lightroom 5, but the problem is there also. I realize Default resolution is best for looking at the pictures, but sometimes you need bigger text. Thanks