I think that is a little bit deceiving because the Fram is VERY light colored media compared to the Prime... there is plenty of light coming through that material.
Here is some more Fram Extra Guard and Prime Guard photos.
Fram leaf spring ripples=a good spot for NO filtration! Sadly, the fiber endcap Extra Guard is better with rippled leaf springs than the more $ high end Frams!
I like the under the microscope views, and don’t know much about filtration. I know a lot about light. I wouldn’t put much into a visual difference about how much light passes. In a mesh it’s not that meaningful. It has more to do with the weave vs the size of any gaps.