Are there any resources online that help to understand perspective and the warping it causes?

When I search, all I get is info on how to use Photoshop's perspective warp. I would like to understand which way I need to adjust my camera to get perfectly centered compositions. I know I could "fix it in post", but there are often objects that give it away. Sometimes, it'll look to me, for... show more When I search, all I get is info on how to use Photoshop's perspective warp.

I would like to understand which way I need to adjust my camera to get perfectly centered compositions. I know I could "fix it in post", but there are often objects that give it away.

Sometimes, it'll look to me, for example, like the bottom and left edges are straight, but the top and right edges are at an angle. So I adjust for that, of course, ending up making my bottom and/or left edges angled... So what want to understand is how the camera affects the angles, and how to adjust for them.

This is for shooting indoor spaces, paintings, things like that.
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