Anyone have an otherwise decent roof prism without phase coatings, maybe in the $200 price bracket? How does it compare to your $100 porro prism? Do phase coatings make that noticeable a difference to the non-expert eye?
I bet the lens coatings on my porro are better than those on my roof, making it a non-even comparison.
I assume the coatings cost more than silver. The silver is actually cheap. It is the chemicals and environmental rules that add cost. Silver or aluminum solve the phase separation, since there is something different about internal reflection vs mirror reflection ... although even water reflection gives everything the same polarity. So I don't know if I believe that.
I wonder what the reflectance is of silver or aluminum from inside glass, and at different angles. I suspect is is different from external reflectance that has protectors or oxidation. I read protected silver is about 98% over a broad spectrum, even though the bare metal is much worse. But those are external reflections in air.