"I just need to do something quick." Tidus isn't really embarrassed to explain, but it's irrelevant to their main mission -- and to their side mission, of gathering reminders of home for Jiang Cheng. So his embarrassment is minimal, moreso than it could be, than the desire not to waste time. He points to the screen, to the symbols present.

"You can hold this, so don't worry about holding the bar. This will take a picture, this is the movie feature... Don't worry about practising, okay? You'll see a thumbnail appear here if you take a picture. Try one now."

Just to see that she understands, so Tidus can brb afk soon, and hurry back and join here!