What this calculator does
The Blink-Free Photo Calculator estimates how many photos you should plan to take of a group to have a good chance of getting at least one shot where nobody is blinking.
How the calculation works
If each person blinks independently with probability p, the chance that a single photo has everyone’s eyes open is (1 – p) raised to the power of the number of people, since all of them must avoid blinking at once. Taking multiple shots follows a geometric distribution: the number of shots needed to reach a target confidence level is calculated as ln(1 – confidence) divided by ln(chance all eyes are open), rounded up to a whole photo.
This is a statistical estimate for general and educational fun, not a guarantee. Real blink chances vary by lighting, camera flash, tiredness, and how long people have been posing, so treat the result as a helpful planning guide rather than an exact prediction.