Originally posted by bbluesman Ahh an expert chimes in
Interesting notes Douglas
Glad I could enlight you!
Dust are important for photographs!
Sometimes an enemy: on the sensor or film slides/negatives. When the Mie-light-scattering of particles in the air turn the sky greyish without a single cloud.
Sometimes an allied: when the particles makes a sunrise or sunset more spectacular.
You might not realise what an effort any lens maker, electronic manufacturer, CCD/CMOS producer etc does to keep dust particles away from their products. They buy loads more particle counters than we researchers do.
In a city you breath between 10,000 and several 100,000 particles per ccm (now considering this is a street shooting thread...the risk is that non of you will dare to change lenses any longer...). This is not good levels to breath all the time. On a 9 million population of Sweden (with half the population living in cities) estimates range between 500 and 5,000 deaths per year due to these particles. More than are killed in traffic. You can scale the numbers to your own city. It will roughly apply everywhere.
In rural areas you have a few 1,000 per ccm. In remote areas, say Northern Canada or Sweden, Amazonas, remote oceans, you have a few 100 per ccm.
When I was on the North Pole, I saw the particle counters go down to 1 per ccm. The air had no smell at all. Cleaner than a clean-room in Pentax lens factories.
Now I will stop. Sorry for going off topic. Don't want to get another infraction.