I try to take pictures of my jumpy cresties on the floor, that way if they choose to jump or run no injuries can happen. It seems to really help to slowly put my hand in front of their face or path and they usually sit still for a while with this method. When I have my camera in focus and it's ready to go I quickly snap a few shots and repeat as needed. I'd recommend handling them in area that they can easily be caught if they do decide to run away, maybe your bathroom or something similar.