Images uploaded to media library after updgarde are all very small

I upgraded to 3.5.1 and now the images I upload to the media library are all 360 x 241 at full size, whereas before the full size was closer to 3900 x 2600. I have checked the images on my computer and they are as big as before, so I’m not sure what’s happening. I haven’t done anything differently (apart from update). Any ideas?