Flatbed's neat sunglasses uses the same process as the astronauts have on their spacesuit helmets...gold oxide that reflects harmfull rays yet minimises
darkness and color change.
I ran a test series....

First from the "outside",,,a beautiful skyshot of the Nolan he just found...full morning sun.



Next, an unfiltered pic into the morning ( cloudy ) sun...



Now a minute later, the same scene with the camera behind a lens..



Compare the two,,,,good color rendition with the glasses...

So why would a digger wear such a high tech piece of equipment ???

Answer, , , , , , , , That crafty Flatbed discovered that at that exact wavelength, objects with a hardness of at least ' 8 ' show up somewhat larger than actual..

Here's the last test pic shooting through the lens of 3 screeners showing their finds.