I shot an engagement session with another photographer. She claimed she has done photography for 20 years but yet she showed up with no external flash shooting at 4 pm! Anyway, she told me that my flash is messing up her focus. Is that statement true? I understand messing up her exposure, I don't know about focus? Oh also she was using a zoom lens that is about 18-100mm maybe? She had the hood rotated wrong. The long sides were on the sides! I didn't tell her because I didn't want to sound like a jerk. I am pretty sure she will see the hood if she is shooting wide. Or maybe this is an advance technique I didn't know about?