>>4474172
Have you even read Ansel Adams, anon?
>I could not find my Weston exposure meter! The situation was desperate: the low sun was trailing the edge of clouds in the west, and shadow would soon dim the white crosses ... I suddenly realized that I knew the luminance of the Moon – 250 cd/ft2. Using the Exposure Formula, I placed this value on Zone VII ... Realizing as I released the shutter that I had an unusual photograph which deserved a duplicate negative, I quickly reversed the film holder, but as I pulled the darkslide, the sunlight passed from the white crosses; I was a few seconds too late! The lone negative suddenly became precious.