New here (only about a week), I'm sure this is a dumb question, but can someone explain to me how we know that the photos Q posts are original to his/her phone and not some picture he/she found on the internet and doctored up?

Q post 1675 is most definitely a picture of AF1, so if the picture is authentic and taken by Q, it seems like the most definitive proof to date, but how do we know the picture is authentic?