Subtle things can really affect your presentation. If you are nervous it can affect the picture, even if you smile. And if you are relaxed and comfortable, it too shows.
After my first makeover, I had my picture taken before we went out to dinner. 11 years later, as she was getting ready to move away, I had a makeup lession with her. I did my own makeup. I wore the same skirt and shoes, and similar bangs in my hair. (The top I wore 11 years earlier was borrowed.)
When I showed her the picture, and looked at it myself closely for the first time, I told her, “I look stiff.” She looked and just nodded. Just feeling nervous that day affected my whole body posture. Feeling confident years later, I just looked more relaxed.
Perhaps you’re feeling something similar. Not being rushed, not worrying about being caught, and just learning to accept yourself changed your face in subtle ways.