images in photoshop are about half the size I have a Mac with integrated retina screen with 2560 x

I have a Mac with integrated retina screen with 2560 x 1440 resolution, if I measure an image on the screen in any other software or browser, I always see it at the same size (100%), but when I load it into Photoshop, the size is the same as About 50%, how can I solve it?

Sorry for my timing, but I translate from Italian with Google