F-Stop to Shutter Speed?

Question

What is the easiest way to determine the equivalent of an exposure of an F-Stop to its shutter speed.

ex. f/2.8 % 500 is equivalent to f/4 @ 250

and f/4 @ 250 is equivalent to f/ @ 500.

Answer 1

Construct a chart - even if it's only in your mind - starting with f/1.0. (Wouldn't THAT be nice???) Every number doubles.
1 --- 2 --- 4 --- 8 --- 16 --- 32
Now, if you can remember any other "usual" aperture, like 2.8, for instance, put that where it belongs and double it the same way. If you can remember to start with 1.4, it is easier, but not necessary. Okay, there are some deviations from the absolute double, but if you have any familiarity with f-stops at all, you will know that there is not an f/11.2.
--- 1.4 --- 2.8 --- 5.6 --- 11 --- 22 --- 45
Now merge them together.
1 ------ 2 ------ 4 ------ 8 --- 16 --- 32 plus
--- 1.4 --- 2.8 --- 5.6 --- 11 --- 22 --- 45 yields
1 - 1.4 - 2 - 2.8 - 4 - 5.6 - 8 - 11 - 16 - 22 - 32 - 45

This is a chart of every "single step" (single EV value) for apertures. Put it on a strip of paper with each value one inch apart from the one next to it.

Now, using the same spacing, put the shutter speeds on another piece of paper, starting with 1/2000. Go along and cut the value in half each time. Just use whole numbers instead of fractions.

2000 - 1000 - 500 - 250 - 125 - 60 (an exception) - 30 - 15 - 8 (an exception) - 4 - 2 - 1

Now, once you know one set of values, like f/2.8 at 1/500 sec, line the papers strips up so those numbers match up. If you used equal spacing on each strip, you can just read the corresponding EV settings directly.

Even if you end up not using this slide rule device, just going through the exercise and studying it for a couple of minutes will show you the pattern and you won't need to use it any more.

Or... Some digital SLR's (and many other cameras, I am sure) do this for you. If you use the "P" mode on a Nikon DSLR, for instance, it will "suggest" an exposure once it has taken the light reading. If you just rotate the command dial, it will step up or down in the same progression as the chart I just described. Nikon calls it "variable program" or something similar.

Once you have worked with it for a little bit, it becomes second nature and it is as easy as making change.

Answer 2

Note to Dr. Sam:

Have you forgotten Leica's f1.0 lens, the Noctilux? For some reason I'm thinking both Nikon and Canon did also. Could be wrong...