diarrhea

When you pro out here look at a photo how can you tell if it has some sort of lens distortion on it? How can you tell? What are the signs/anatomy of a lens distortion?

fotobill

There are different types of distortion. Some lenses may have barrel disstortion or pincushion distortion.

Are straight lines curved, more pronounced curvature near the edges?

Are things that should be the same size not the same size in the center as they are toward the egges?

A very wide angle lens may have things at the edge smaller because they are actually further away than the center items.

Are circles true or stretched?

These are some things that come to mind, I hope it helps.