See, I live in an old apartment. The corners aren't 90°, the wall a picture is hanging on is convex. When I'm lying in bed and look at the picture it looks like it's crooked but I used a level several times on it and it's as straight as can be. It's driving me insane.
I worked on an industrial robot once, and we parked it such that the middle section of the arm was up above the robot and supposed to be level. I could tell from 50 feet away and a glance that it wasn't, so we checked. It was off by literally 1 degree.
Degrees are bigger than we think, but also our eyes are incredible instruments.
I remember we once installed something on a beam 40' feet up. While waking through an inspection of many such things, the engineer stops, cocks his head for a second, and says "that's not quite straight"
And then it wasn't. Like a cast of manual breathing, the thing I had been frequently walking past for weeks was suddenly wrong, ever so slightly
Nah, we just went up and fixed it. I think I did it while the guy on the ground eyeballed it... It's weird how it's impossible to see up close, but from 40 feet away humans can tell to a fraction of a percent, I was tapping it with a wrench to dial it in based on the intensity of hand gestures. Honestly, we were more impressed by how he spotted it at a glance, it's not like we did shoddy work - it was barely not tongue click, as he put it
It helped that I liked the engineer. Always cheerful and he gave me mini multi tool pliers for my birthday. Totally unexpected and not expensive, but I've got them right next to me right now, I still use them years later. And he was like that to everyone - he was a stickler for the details, but actually took an interest in us as people
Just a good guy all around. It's hard to be upset with someone like that, even when they make you redo work now and then