What’s the correlation between the exposure time of your photographs and the time of the day?

My digital photo archive spans 15 years and holds about 12,600 pictures (not so many, after all). I’m curious to see if there is a correlation between the exposure time of my photographs and the time of the day they were taken. A rather simplistic observation, perhaps.

In short: there’s nothing spectacular about this correlation, but it’s nice. The morning hours are the ones with the lowest average exposure (the plot is reversed, so you can look at familiar integer numbers) time at around 1/320 s between 9 and 10 AM. There’s a sharp increase between 12 and 1 PM, then it increases again after 4 PM towards dusk. I don’t take many pictures at night!

See for yourself.


The most frequent values for exposure time are in the table below. 1/30 s is the typical exposure time when using the flash, and it’s recognisable in the plot above.

1/n s occurrences
800 1986
1000 1178
30 943
400 547
250 488
640 458
200 450
500 388
320 342
160 337

The Python and R scripts are at https://gitlab.com/steko/expotime (giving GitLab a spin since GitHub is a monopoly and I don’t like that). I’m still doing some experiments with the source data, then I’ll upload those as well.