[ChrisM]

With photographing rotating lighthouse beams, the challenge was to get enough exposure without blurring, so maximum ISO and maximum aperture.

Both pics: Nikon D7000, 17 mm, ISO 12800, f/2.8
First pic 0.6 secs
Second pic 3 secs. Castle Rock, approximately 1 km away, is partly illuminated by the beam.

Chris