I just remembered this, but many years ago when I was in Sacramento CA we had misrable "Tule Fog" in winter that reduced visibility to 600 and even 0 feet. One day it was so thick I had to drive with the car door open and look down at the barely visible dashed line. The end of my car hood was all I could barely see.
more info here: http://en.wikipedia.org/wiki/Tule_fog
I don't know why I did it, but one foggy day I put on my Revo Polarized sunglasses (long before the Luxmonster ruined them) and my range of visibility increased from 50 feet to about 250 ft (tested using a speed limit sign). I could not see great, but I could make out objects that were previously invisible, such things as bridges, intersections, roads and other cars... not exciting stuff but nice to see when you're driving.
With the fog filtering about 70% of the sunlight, and my sunglasses reducing that light another 90%, I was only getting 3% of available light, but I still could see dramatically better with sunglasses than without. The net difference in contrast was startling.
I tried out a Polar Brown A lens, adding yellow and red tint (orange) and throwing on a Blue Mirror coating on front, and backside A/R, with about 50% transmission. The result was amazing. In days I could see only a hundred feet without glasses I could see objects at almost 1000 feet with them.
After I did a pair for a trucker, I ended up doing about 40 pairs of these for the California High Patrol and a bunch for other truckers (our office was near the Highway Patrol office) (its good lesson too on how powerful one referal can be).
So in my case the reduction in total light was more than offset by the increase in contrast over distance due to the reduction of glare. Glare dropped at faster rate than the incoming light did, so contrast increased.
Unfortunately there is no effective way to measure "glare" itself apart from ambient light, glare is inherantly subjective, so there is no way to formulate this mathmatically. But, if you have an extra frame around, you might try a pair next winter if you get fog where you live. They work great.
Maybe glare has some type of threshold that if we reduce it enough contrast increases despite the net loss of total light. At least that's the theory I'm toying with.
Sharpstick
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