Might be a good idea to stare at the light reflected from a white sheet of paper. The wavelength won’t change but the intensity (and FOV coverage ) certainly will

How about putting a diffuser (like a sheet of paper) in front of it?

Of course! The red LED is actually fairly dim, it's designed for pilots trying to read charts while flying at night!

I got it for use with a telescope for looking operating a telescope without losing night vision.