I comprehend fine; you fail to understand the objection.

You may intend to have no "pre-formed conclusion," but simply by being an average person with an ordinary background you already have pre-formed opinions about how things are supposed to look.

You can't help it. They are already there. And many of them are wrong.

The only way to actually perform this neutral observation we both agree is warranted, is to have sufficient education in perspective, optics, the behavior of cameras and film, etc., to be able to spot the illusions and false expectations you otherwise bring to the table without even knowing you have them.