"On top of Maxwell Montes the air is 43 bar at 648 K, but I'm not sure how that translates into visibility distance - the Venus surface views all seemed very clear from all the Venera camera shots and I'm unsure how much scattering happens in CO2 over the distances involved at the visible frequencies that get through all those clouds. At 30 km I think it's the base of the clouds and starting to get hazy with sulfuric acid droplets and those mysterious particulates. Air is about 15-10 bar at 550-510 K. All the action seems to be in the clouds. "

Is it sulfuric acid or sulfur dioxide?
"Minor (ppm): Sulfur Dioxide (SO2) - 150; Argon (Ar) - 70; Water (H2O) - 20;
Carbon Monoxide (CO) - 17; Helium (He) - 12; Neon (Ne) - 7"
http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html

Seems like it's pretty dry around there for sulfuric acid.
But both are colorless substances, requiring droplets to scatter light. And if you have large droplets what stops them from falling as rain- sure, it won't hit the ground but it's transferring energy- so, how much does it rain on Venus?
SO2: 150 ppm might seems insignificant, and Water: 20 ppm even less. But these parts per million are of the entire atmosphere, if it's "raining" say 10 ppm of that H20 per year, you are in range raining more than it does on earth per year, and in that range one dealing with a lot energy being transferred.

Now, apparently all the action involving clouds is occuring in less than 1 atm of Venus' 90+ atm atmosphere. Is the 90 atm Venus atmosphere the purest of the pure and all the "muck" in the 1 atm or less. Or is there some impurity in the 90 atm and far less muck in the 1 atm or less.
And when we speak of Venus could divide it into how much ppm of SO2 and H20 is in the cloud area.
In other words, I want ppms below 40 km and the ppms above 40 km. Or below cloud deck and at and above cloud deck.

Now, let's return to the top of our mountain with 43 bars at 648 K. One km of this 43 bars is similar to looking through 43 km of 1 atm of CO2. And 10 km of this 43 bars is similar to looking through 430 km of 1 atm. Has anyone looked through [in visible spectrum] 430 km of 1 atm of any kind of atmosphere anywhere?

Regarding the Venera camera shots, are there any shots in which show a distance of more than 1 km?