Exposure Values

An Exposure Value is one which tells you which Aperture Setting and which Shutter Speed
setting is needed to achieve the same exposure.
For instance an Aperture of F16 at a Shutter Speed of 1/125 will give me an EV of 15.
So, with this is mind I can set various permutations of apertures and shutter speeds, for
the same illuminated scene.

Below is a table of all useable Exposure Values, that you will encounter,
in the beginner-intermediate levels of photography.

The aperture values are in Blue, the shutter speed values are in green and the EVs are
in red.

To use this table, use the F16 rule as an example;
The table shows that at F16(blue), follow down to 1/125 (green),
then across to find that the EV for F16 @ 1/125 is 15.

With this in mind you can also say that for the same EV (in this case-15), that....
F2 @ 1/8000, F8 @ 1/500 and F22 @ 1/60, also have an EV of 15.
This table shows 11 such permutations for EV 15.

Some typical scenes