What tends to be confusing for most of us - in our quest to understand aperture - is that the
aperture size (f-stop number) seems to be backwards. The larger the f-stop number, the smaller
the aperture opening! The smaller the f-stop number, the larger the aperture!
Why?
The f in f-stop stands for function. The function used to determine the aperture is a mathematical
thing with a lot of complex calculations. Fortunately, for our purposes we won’t need to get an
advanced degree in mathematics to understand how to work with the aperture settings.
NOTE: This is NOT a mathematically correct explanation, but it will do the job to help us
understand what a function is and why a larger number is a smaller hole in the lens.
Just think of the name of the aperture (hole) size as a fraction with 1 as the numerator. So f- 4
could be thought of as 1/4. F-8 then becomes 1/8 and so on.
Considering fractions, we all know that 1/4 is a larger number than 1/8. When we think of an f-
stop as a fraction, we can see that f-4 is actually a larger hole than f-8. F- 16 would be a much
smaller hole than f-2!
In macro/close-up photography, to solve our shallow depth of field issues, we have to use as
small an aperture as our lens will allow.
I find it to be hilarious that you can take a landscape photo and have it be in sharp focus all the
way to the horizon, but when you try to shoot an insect, one side can be in sharp focus while the
other side is nothing but a blur.