When people take these shots of their abs, are they flexing as hard as they can to make the six-pack show?

[Couchpotato1999]

I am just wondering because I do a lot of weighted sit ups (with a 45 pound weight), and my abs don't look like that when I flex. For example is this guy flexing here?

[Markasaurous]

They have what is called a "pump" meaning they exercise and get their muscles pumped before the picture making them look bigger. Same goes for arms or any other part of the body, if you lift weights your arms look bigger and stronger with veins popping out because of the "pump".

Also, the lighting has a ton to do with it. And their genetics.
Also, their muscle, it is possible for it to be defined, not sure about these guys but close enough.