First off, new to mac, so bear with me. I have downloaded photos from my camera to my macbook pro 13" and want to transfer them to my ext hdd so as to save space on my internal SSD. Each time I try to do this, the Photo Application will not allow this. I can do this on my Photoshop software, but not on the Apple Photo app. Am I missing something here, or is there a simple item I am overlooking. I generally get a message saying "could not write files to destination (1016). Am almost at the point of just deleting photos and starting over.