Many of the trees here in eastern Iowa have continued to hold their leaves this year. It is a little later in the year than normal. Last night, the temperature got to 26˚F which prompted a phenomenon called abscission. This morning in the warm sunshine, the leaves started dropping quickly. We’ve watched this occur each fall for many years as cold weather approaches.
I have an app on my iPad called NightCap Camera. It is normally used for low-light and night sky photography. One setting is for lines left by moving objects. The iPad is set to be stationary while the exposure takes place. It captures sequential images recording locations of objects that moved during the exposure. It works in the dark or daylight. This first image was about 20 sec. Exposures of 1/288 sec were recorded as the leaves dropped.
Here is a second image lasting about 2 minutes. This a visual definition of fall.