Explain how cinematographers achieve the "inside the camera" look.

It’s a cell they add in post.

Ahhh, thanks!

Or a cardboard cutout taped to the lens….

What is “a cell they add in post”?

Sorry- it should be ‘cel’. It was four am so I plead the first sip of coffee.

And “post” means “post-production” or editing. Once the photography is complete, a film goes into post-production, and the director and editor “cut” the film to the director’s satisfaction. In post, the editor can add effects, such as “from the camera’s lens” view, with computer software like Final Cut Pro.