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Language of Stop >

A flower bed was photographed with the light of a full moon.

The photograph looks like it was taken in daylight because daylight was used.

That is, the sunlight reflected off of the moon was the light source.

We expect moon light to be blue.

That's because film makers use a blue filter for day-for-night scenes.

Click Photograph to Enlarge

The exposure was as follows.

ISO 1600

f/8

60 Seconds

How would the above numbers change if we "trade" stops between the three countries?

Let's change the ISO from 1600 to 100.

That's a four stop change.

We have to trade four stops.

Let's trade between ISO and lens opening.

The new lens opening is f/2.

ISO 1600	f/8	60 Seconds
ISO 100	f/2	60 Seconds

We traded four stops from the ISO to lens opening.

The ISO is now four stops less sensitive.

The lens opening now gathers four stops more light.

1 Stop	1 Stop	1 Stop	1 Stop
f/8 to f/5.6	f/5.6 to f/4	f/4 to f/2.8	f/2.8 to f/2