Have some Pi

Pi = 3.14159265358979323846

At the time of this post, I can recite the value of Pi to twenty decimal places!

Why would anyone bother you ask? Great question! I seem to recall a time, during my high school years, where recalling the value of Pi to three decimal places gave me pause to think. I am sure it was due to the fact I was not interested in anything to do with Pi at that time. Today, I have a real world practical application for it.

It wasn't until I became interested in photography that I rediscovered Pi.

Now, anyone can capture photographs, with a camera, without knowledge of the value of Pi. However, I am curious and I like to know how certain things work.

Pi is necessary in the mathematical formula used to calculate the area of a circle. The area of a circle is calculated by taking the radius of the circle squared times Pi. The formula has been around for a long time.

The formula for calculating the area of a circle can be put to good use in deriving the area of an aperture in a photographic lens. As aperture controls the quantity of light entering the lens, one can understand and describe the relationship of lens F stops used to control image exposure. In other words, one can understand why f/4 lets in twice the light as f/5.6.

So, now I have the answer to the question I asked myself many years ago. What will I ever need to know the value of Pi for in real life?

I should point out that twenty decimal places of precision for the value of Pi is not required to calculate a reasonable area result for a circle. The more precision you use the more precise the area. I just memorized the decimal places as a fun exercise.

According to the Guinness Book Of World Records, at the time of this post, Chao Lu, of China, recited Pi to 67,890 decimal places on 20 November 2005. Given that tidbit of information, twenty decimal places doesn't seem noteworthy.