Created by Aleksandra Zając, MD
Reviewed by Dominik Czernia, PhD and Jack Bowater
Last updated: Jan 15, 2023

This blink-free photo calculator is the perfect tool for curious people who love to apply science to everyday life. It tells you how many photos you should take to be (almost) sure that nobody blinked at the wrong moment.

Have you ever wondered how many times you blink a day? Or why we blink at all? We've got the answers ready for you! Were you ever annoyed by that cousin who always blinks in your family photograph? Well - you are not the only one! The eternal question of how not to blink in photos resulted in interesting scientific research... and even an Ig Nobel Prize!

We blink all day, hardly even noticing that we're doing it. Why? Well, blinking is a reflex - that means our bodies do it automatically, without even thinking. So why is it so important - why do we blink?

• It is a protective reflex - you might have noticed that when an object suddenly approaches your face, you will close your eyes immediately to protect them;
• It takes care of your eyes - with every blink, your eyelids cover your eyes in a secretion - a mixture of water, oils, and mucous. This keeps your eyeballs from drying out;
• It keeps your eyes clean - blinking brushes aside the tiny particles of dust that are floating in the air and removes any particles on the eye with water. Do you remember going out on a windy day and blinking more frequently? This is because the wind was carrying more dust than usual, as well as that air movement drying out the eyes;
• It fights against infections - tears contain substances that kill bacteria and viruses, and squinting spreads tears;
• noticed that blinking might play a role in cognitive behavior. Their theory is that every blink is a short break for the brain, which helps us stay focused throughout the day.

The length of a blink varies between 100-400 ms, and the average person blinks about 15-20 times a minute. That gives us 900-1,200 blinks an hour, which is 14,400 – 19,200 times a day. Now you'll no longer be caught unaware if the question "How many times do you blink a day?" comes up in your next quiz. 😎

The frequency of blinking depends on various factors - emotions, health, and even the weather. Your age and sex don't really influence it, though.

• You're in dry air or a windy area;
• You're stressed (don't worry about a good blink-free photo if you're nervous about it), anxious, or tired;
• You're exposed to smoke, irritating smells, etc; or
• You've got an inflammation in the eye area - like conjunctivitis or even hordeolum.

The blink-free photo calculator is easy to use. It pre-filled with an example group of five people so you can understand how it works intuitively. But let's walk through it together!

Fill the field for the group size. You'll immediately see the chance probability that the photo will be blink-free.
Below that, we also give you how many photos you'll have to take to be 99% sure of a good photo. We've counted it using the following steps:

1. We have already calculated the probability of success ($\mathrm{PS}$). We can express it using the probability of failure ($\mathrm{PS}$) symbol:
$\mathrm{PS} = 1- \mathrm{PF}$
1. We want to make sure that the photo will be okay. So, let's compare the probability of success to a number that will satisfy us. Let's say 99% (because 100% is nearly impossible):
$\mathrm{PS}≥ 0.99 \\1 - \mathrm{PF} ≥ 0.99$
1. But hey, we have multiple tries here! We raise $\mathrm{PF}$ to the power equal to our number of trials ($\mathrm{T}$) needed.
$1 - (\mathrm{PF})^\mathrm{T}≥ 0.99$
$T≤\log_{(\mathrm{PF})}(0.01)$
1. Finally we'll change the sign ≤:
$T≥-\log_{(\mathrm{PF})}(0.01)$

Let's see an example for a group of five!

We know the $\mathrm{PS}$ from the calculator.

$0.8154 = 1 - \mathrm{PF} \\\mathrm{PF}=0.1846$

To be 99% sure that we get a blink-free photo, we need to take T pictures:

$T≥-\log_{(\mathrm{0.1846})}(0.01) \\T ≥ 2.7257$

Since we can't take half a photo, we've rounded the result up to three.

This example assumes good lighting conditions. When there's bad light, e.g., at noon on a sunny day, people might blink more, and so we assume that an average number of blinks gets closer to the maximum of the physiological range - we use a value of 15 times per minute.

Now you know how to count the number of trials needed to get the perfect picture - and so you can use this method whenever you want. Or, you can take it easy and make the blink-free photo calculator do the work for you. 😉

How to not blink in photos is a mainstream problem, but only a two people found it so upsetting that they decided to put science to work: Nic Svenson and Dr. Piers Barnes from (Commonwealth Scientific and Industrial Research Organisation). Svenson was annoyed that in the group photos she took, almost every time somebody had their eyes closed. She wondered how many times she would have to repeat the photo to get the perfect shot... so she asked her friend, Piers Barnes, for help.

Nic Svenson and Dr Piers Barnes ()

2. On average, a person blinks 15-20 times per minute. But when somebody is taking a photo, you try not to blink too much and so the mean frequency drops to ten times per minute.
3. A blink lasts for 250ms = 0.25s.

Then Dr. Barnes came up with the formula for calculating the probability of one person not blinking in a photo:

$P = 1 - x × t$

where:

• $P$ - probability;
• $x$ - blinking frequency = 10 times/ 60s; and
• $t$ - length of a single blinking = 250ms = 0.25s
$P = 1 - 10/60s × 0.25s = 1 - 2.5/60 \\P = 1 - 1/24 = 23/24 = ~0.96$

So, the probability of one person in the photo NOT blinking is 0.96 (or 96%). If we want to find the probability for a group photo, we have to raise the probability to a power, where the power is equal to the number of people in the photo.

Let's have a look at an example for six persons, where we want to find the probability of a good photo:

P = 0.96⁶= ~ 0.78

$P = 0.96^6= \text{\textasciitilde}0.78$

For their discovery, the scientists received the , a prize for 'achievements that make people LAUGH, then THINK'. The prize has been given out annually since 1991 and is run by the , a scientific humor magazine. The prize's name is a nod to the , which the Ig Nobel prize parodies, and a wordplay - think ignoble.

You know now why we blink and that it is natural and healthy. Still, when taking a photo, you would love the world to see your lovely eyes. And, if you're a photographer, you've probably had nightmares of group photos, where everything is perfect... Except for that one person with their eyes closed! Let's look at some tips both for posing and photographing people - so that you've got pictures that you would like to present to everybody!

If you are taking a photo:

1. Don't make them 'SMIIIIIIIILE' by saying 'SMIIIIIIIILE'. It will look unnatural and enforced;
2. Instead, ask them to look slightly down and then raise their gaze at 'three', when you count to three;
3. Another method is to ask the group to close their eyes completely and open on 'three'; and
4. Try asking people to blink on purpose on 'two', when you count to three. This will give a natural look on 'three', when you press the shutter.

How to not blink if you are posing for a photo?

1. It sounds trivial, but try to relax ☺️;
2. Don't forget to breathe;
3. Think of something that makes you smile with a hint of joy, like babies or puppies; and
4. Listen to the photographer's instructions. If they don't provide you with one, close your eyes slightly and open them just before they finishes counting - you won't have time to blink randomly another time before he takes the photo.

Interested in photography? Make sure to take a look at the following:

Aleksandra Zając, MD
Number of people
Light quality
Good light
Probability
80.83
%
You've got a 80.83% chance of taking a blink-free photo when photographing a group of 5. 📸

You have to take 3 photos to be 99% sure you'll get a good one. 🤳 🤳

Below, we present you a chart ilustrating how many attempts you should try while photographing a certain number of people. 🧑🏻‍🤝‍🧑🏻

Hit the 'Advanced mode' button to customize the chart to suit your needs.
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