From the blackness, a spark of light
A struck match from a Mammoth Cave ranger illuminates a cave so that his tour group can see how dark caves get. All lights went out for a few moments. The pitch black was a little overwhelming to some of the children. The penlight helped calm nerves and adjust eyes to a dimly lit cavern.
Technical note: in a place that has little light, ISO 25600 is as much as I can push this camera and fisheye lens but the image definition suffers. I can use a lower f-stop but I was worried that the depth of field would be too narrow for estimating the focus distance manually.
It's really dark.