Changing the Aperture and Shutter Speed without changing the exposure…

…and not changing the ISO - When you change the aperture from f 8 to f 11, the amount of light is cut in half - likewise, when you go from f 11 to f 8, the amount of light is doubled.

When the shutter speed is changed form 1/125 to 1/250 the length of time the is cut in half - like wise, when you go from 1/250 to 1/125 the length of time is doubled.

For instance, an average exposure on a bright day outside at ISO 100, the basic exposure would be 1/125 @ f 11

Take for instance this scale:

f stop f 4 f 5.6 f 8 f 11 f 16 f 22 f 32

shutter speed 1/1000 1/500 1/250 1/125 1/60 1/30 1/15

Each one of these setting will give you the same exposure - by cutting the amount of light, and doubling the amount of time the shutter is open, it gives you the same exposure. by doubling the amount of light, and cutting the amount of time the shutter is open, it give you the same exposure. WHY DO THIS . . .

If you want to increase / decrease your DOF (depth of field)

If you want to stop action

There are trade-offs for each!