[edzo4]

from the article you posted:

"This was actually taken with "Cam4", which is a little wider angle than Cam2 and pointing in the same direction."

and

"It is a Canon T3 Rebel set up as a webcam. Images are captured about every 40-45 seconds. 3.5/20 second exposure/ 1600iso. I only run it on clear nights or when there could be severe weather."

so see where it says 3.5/20 that means the wider angle was a 3 to 5 ratio and exposed for 20 seconds, so instead of the angle I posted earlier which was a 1 to 1 ratio and at 10 feet from the lens it had a 10 ft field of view this particular camera would have a 50 ft field of view 30 feet from the lens or if 3 miles away it would be five miles wide and an even greater distance to travel before leaving the frame than I had previously speculated.

[Jack Black]

In photography lenses and exposures are almost always described as f-stop, lens focal length.

The full way to write that would be: f/3.5 20mm and if you were going to be complete, an exposure time like 1/100th of a second.

According to this Nikon table a 20mm lens has an 84 degree horizontal angle of view.

yours, MrEverythingfag