I am struggling with remembering fstops and hot to utilize math in conjunction with aperture. I understand that the largest aperture is 1.0 and everything below is a fraction but cannot understand/memorize the math that is involved when switching fstops. Is there a guide/graph out there that explains fstops and a simple way to remember how to calculate between stops?

Thanks,

Deaner

## Comments

I don't think there's an easier way of remembering the stops than just to memorize the common full stop numbers. Shutter speeds are direct - half or double the speed is a one stop change. ISO numbers are also direct - half or double the ISO number is a one stop change as well.

On the D3200 and I presume the 3100 as well, the electronic selector proceeds in 1/3 stop increments. Three clicks moves you a full stop. So if you have a desired exposure value that says "this speed at this F stop", you can change the speed by one click faster, and restore the exposure value by changing the aperture one click wider. If you are shooting manually, and start with the meter's recommendation, each click represents a 1/3 stop deviation.

Here's a chart of equivalents if you want it on paper. Many charts of varying complexity exist and can be found if you hunt.

http://lynnfreeny.blogspot.com/2013/01/charts-to-help-you-better-understand-f.html

Here’s my own strategy for remembering them:

7 of the 10 stops are whole numbers. That is: 1, 2, 4, 8, 11, 16, 22

So if you’re taking a written test, write them out first. Start with 1. Then multiply it by 2 and write down the number. Repeat this 3 more times and you’ll come up with 1, 2, 4, 8, 16.

Most lenses have a minimum aperture of f/22, so remember that and write it down. Half that number to get 11.

Put the numbers into sequential order and you now have 7 of the 10 aperture stops.

The other 3 stops are 1.4, 2.8, and 5.6. You’ll need to just remember them somehow. For me, I find it easy to relate them to something concrete.

For example:

f/1.4 is the max aperture of most high-end primes.

f/2.8 is the max aperture of most fast zooms.

f/5.6 is the max aperture of the kit lens at the long end.

(Or you could just remember 1.4 and then its next two multiples of 2)

Again, put the numbers into sequential order and you’ll end up with the 10 full stops between f/1 and f/22.

Once you have a firm grasp of what the full stops of aperture, shutter, and ISO are, it becomes simple to adjust the aperture and then compensate.

Let’s say you start off with your exposure at f/2.8, 1/30, ISO 400.

You now want to shoot at f/5.6 which means you reduced the amount of light by 2 stops.

So if you want to maintain the same exposure, you must compensate those 2 stops of light with shutter and ISO.

The options are:

f/5.6, 1/8, ISO 400 (slowed shutter by 2 stops)

f/5.6, 1/30, ISO 1600 (increased ISO sensitivity by 2 stops)

f/5.6, 1/15, ISO 800 (slowed shutter by 1 stop and increased ISO sensitivity by 1 stop)

1 x 2^0 = 1

1 x 2^1 = 2

1 x 2^2 = 4

1 x 2^3 = 8

1 x 2^4 = 16

1.4 x 2^0 = 1.4

1.4 x 2^1 = 2.8

1.4 x 2^2 = 5.6

11 x 2^0 = 11

11 x 2^1 = 22

So you just need to remember 3 numbers (i.e., 1, 1.4, and 11) and then take their powers of 2. Then put them all in sequential order.