Want to know how many pictures you need to take of a group of persons, to be statistically sure noone has their eyes shut or is in mid-blink? Admit it. Intriguing, isn’t it? It is even more intriguing to know that there actually is a formula to take care of that:
1/(1-xt)n
where:
x = the average number of blinks per second of a person
t = the camera’s shutter speed plus de duration of an average blink
n = the number of people in the group
A little bit complex, isn’t it? But here’s the rule (applicable to groups smaller than 20) condensed into an easy manner:
- In good light, divide the number of people by three
- In darker conditions, divide by two (with the shutter open longer for a better exposure, there’s more time for blinks to creep in)
For this discovery, Nic Svenson and Piers Barnes won the 2006 [Ig Nobel prize] - an annual award that recognizes zany scientific research - in the mathematics category. You can read more about it [here]
Obviously, this rule does not apply to people that pathologically shut their eyes when pictures are taken of them, like Earl:
