The thing you have to remember with male porn stars (and forgive me if it's been discussed before) is that very few of them are over 5'7" in height. Jeff Stryker, one of the biggest stars in 80's gay porn was insulted when they added an inch to his size to make the dildo cast from his penis, from 7" to 8". You take 7", put it on someone 6'4", and it's going to appear tiny (in contrast) to the same size on a much smaller guy. If I remember, Jonah is 6'2", and I'm sure there might have been a few porn stars much shorter with close to the same size that would look much bigger. John Holmes was at least 2-3 inches shorter.
Then again, you have the real giants like Ken Ryker who is 6'5" and a very real 10"+.
In porn, as in all photography, it's all a matter of proportion (and not just camera angle and lens selection, although that can help too), and most of the female stars ever top even 5', which, in proportion, makes even 6" on a 5'6" guy look huge.
So when trying to judge penis size from any photograph or video, you have to always take into account the height of the people involved. Even long before porn most screen actors were "much smaller in person" because other attributes like eye size, eyelash length, density of hair (and five o'clock shadow) qualities that most people perceive as "attractiveness" come from being much shorter (and smaller bodied) than average. Although there are some exceptions, as in any generalization.
And of course, the less fat anyone carries on their body, the more blood supply there is for everything else...
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