Blink-free Photo Calculator

Why Group Photos Catch Blinks

A typical blink lasts about 250 ms. In posed photos people blink less often, around 10 times per minute in comfortable light, or closer to 15 times per minute in harsh glare. CSIRO researchers Nic Svenson and Piers Barnes used those facts to estimate how many frames you need. Their work later received an Ig Nobel Prize.

Blink-free Probability Formulas

Chance that one person is not blinking during the shutter:

$$P = 1 - \frac{x}{60} \times 0.25$$

With $x = 10$ blinks per minute, $P = 23/24 \approx 0.9583$. For $n$ independent people:

$$P_{\text{group}} = P^{n}$$

Number of independent shots $T$ needed so that at least one frame is blink-free with 99% confidence:

$$T = \left\lceil \frac{\log(0.01)}{\log(1 - P_{\text{group}})} \right\rceil$$

Five people in good light have about an 80.83% chance on one frame, so three shots reach 99% confidence.

Related tools: Camera Tool and Among Us Impostor Odds Calculator.

Frequently Asked Questions

Why does chance drop so fast as the group grows?

Each extra person multiplies the one-person success rate. Even a 96% individual chance becomes about 81% for five people and about 66% for ten.

Does shouting cheese help?

Forced smiles often look stiff and can increase blinks. Count to three, have everyone look down then up, or blink on two and open on three.

Are blinks independent?

The model assumes they are. Real groups can sync a little from the same countdown, so treat the result as a planning estimate, not a guarantee.

What shutter speed does this use?

It uses blink duration (250 ms) as the window when closed eyes would show, not your camera shutter. Fast shutters still catch a blink if the lid is already closed.

Should I take more shots outdoors at noon?

Yes. The poor-light setting uses 15 blinks per minute, which lowers group success and raises the shot count.

How many times do people blink in a day?

At 15 to 20 blinks per minute you get roughly 14,000 to 19,000 blinks in a 16-hour waking day.

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Why Group Photos Catch Blinks

Blink-free Probability Formulas

Frequently Asked Questions

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