Sunset?
Hi gb
The clouds on Venus are formed continually out of SO2 and H2O reacting and making H2SO4, which then drifts down into the heat and is decomposed back into the gases. Thus the 30 km basement of the clouds - that's the level the vapour gets cool enough to form the droplets out of the component gases. No rain ever hits the ground as the droplets evaporate and the sulfuric acid is broken down before it gets close. Maxwell Montes is still too hot by about 35 degrees for sulfuric acid to be stable.
As for air columns sunlight has to travel through a lot of air when it's near the horizon, so that might make for a fair comparison.