Mirror vs. Photos--anybody else?

I often check myself in a full length mirror--just to see if my clothes are on right side out etc. and when I do that I see "me." I don't think I have lost that much weight--objectively I know because I'm comfortably fitting into a size 8 and started as a 14, so while I objectively know I am smaller, the image in the mirror still looks like my usual old lady dumpy self--just smaller.

We hosted some friends over the weekend and she's all about constant photos and selfies--I usually avoid trying to be photographed, but had to be polite. She sent me a couple of the photos and I was shocked at how different the picture was from what I see in the mirror--I actually look fit and trim.

Why do photos look so different than what we see in the mirror?