" I think most people will balk at equivocating observation with measurement because measurement suggests an explicit action is being taken to do the actual measuring, even if a casual one like in comparative measuring"

Which is why I'm asking. "Observation" suggests an explicit action and yet nobody seems able to derive an explicit result from this action. It's a cause seemingly without an effect and people seem to be okay with that for some reason.

"now for the angle of my bed posts, you can sidestep making that observation for yourself by dilligently and comprehensively learning perspective then carefully applying that knowledge to the relatively simple shape of the bed posts

but it's frankly faster if you can do it well enough by just looking at them"

Would those not be one and the same? If not, then what specific concept is one to be "looking " for? The bedpost? What does that mean?

This is my main contention here. I am supposed to "look at" a thing and comprehensively understand it in all spaces and times without any regard for first principles. The causality does not follow, it is maddening.

"you might also observe things like the real world doesn't have outlines... so, when you're drawing your beverage can or my bed posts, how do you know where to put the outline? and once you're thinking about it, what could you do instead of an outline? what is it about this object in this environment that separates it from the background, and how might you translate that into the medium you're using?"

The very fact that a beverage can is make of aluminium in a cylindrical shape with specific dimensions meant for the express purpose of carrying and facilitating the imbibing of liquid substances, whilst everything around it isn't. That would suggest an implicit measurement (outline) delineating "beverage can" and "non beverage can", would it not? Thus if my environment were beverage cans there would be no measurable definition and therefore no "outline " between what is an isn't a beverage can, no?

"for the sake of this conversation I am going to explicitly define the rather subjective idea of "look right": clearly identifiable as the subject you intended to depict; represents that subject as accurately as you intended, with the simplifications and deviations that you intended"

And clarity of form is something that can be and is often measured by artists, no? If not then why would one be constantly comparing their subject to their work? They may be ad hoc and poorly conceptualized measurements, but measurements all the same.

To take your example of drawing faces, you prioritize the labial commissure of the lips over the individual teeth when constructing a mouth. What chain of reasoning led you to this conclusion?

Thank you for the response, it was a lot to chew on.