People always seem to compare The Conversation to this and say that both films are different ways of expressing the fact that you can see/hear something on a sensory level but still not understand what it is. The Conversation is about that, certainly, but it only forms a small part of this film. And I love The Conversation, but this one digs a lot deeper. The Conversation asks is “can we understand what really happens by just perceiving it?”. The question Blow-up seems to ask, at least partly, by putting its main plot on the backburner until late into the film are “do we care to understand?”. (semi-sort-of spoilers):

It’s might not be just that Hemmings’s character is trying to comprehend something that’s incomprehensible, it could be that he’s too distracted and exhausted to bother comprehending something that simply seems incomprehensible. I love the setting of swinging London, and almost feel like it was meant to seem dated for future audiences, because it easily shows the ridiculousness of it all. We go apeshit over things that are popular in the moment, but then when the moment’s gone, no one cares anymore. Like the scene with the Yardbirds. Our pleasures and conveniences distract us, make us fickle, and distort our reality away from some sort of notion of absolute truth.

But at the same time, maybe what Hemmings was trying to understand was really impossible, even if he didn’t get distracted. The final scene seems to illustrate this. Reality, if it exists, is awfully confusing. Who says what you’re seeing is the right thing? Who knows if there is a right thing you should be seeing? Who knows if what you’re seeing is even real or not, and isn’t just a projection of things you imagine to be there? Maybe we realize this and, because the world is so ridiculous, we absorb ourselves into the ridiculousness and turn off the part of our brains that has any notion of fundamental truth. When someone like Hemmings tries to turn that part of their brain back on, they get burned.

I’m still struggling to get a clearer interpretation, but a clear one might not be necessary given the plot. Anyway, it’s a great film, and one that you should be patient with.