Is it possible to save to my disk from the photos app?
The other way, which takes a (very) few more steps, is to click on the photo you want to save to your disk. Then, in Photos, go to File > Export, and choose to export the edited photo (shift - command - E), or the original unmodified file. You will then be presented with some options as in the picture below, and when you click "Export," you can even choose where to save the picture. Works great.