Shutter speed calculator for sharp people pictures

The two rules behind it

For your hands, the old rule is one over the focal length: 1/85 for an 85 mm lens on full frame. On a crop sensor, multiply the focal length by the crop factor first. On a high-resolution body, double it, because more pixels show smaller shakes. Each stop of stabilisation halves the speed you need, though real-world gains are usually a little below the number on the box.

For the people, rules of thumb from wedding and event work: about 1/125 for posed portraits, 1/250 for walking and talking, 1/500 for dancing, 1/1000 for running children or sport. Hands and hair move faster than faces, so the edges of a frame blur first.

The calculator takes whichever of the two is faster and rounds to a speed your camera offers. That is the whole method, and it is deliberately cautious: a frame you can't use costs more than a little extra ISO.

Read the last column twice. On a dance floor, stabilisation makes almost no difference, and the lens barely matters either. People who have pushed to 1/60 with a stabilised body and wondered why the first dance came back soft are seeing exactly this.

When the light won't give you the speed

• Raise ISO before you slow down. Noise can be cleaned up; motion blur can't.
• Shoot short bursts at the peak moments. One frame of three is often sharp when the other two aren't.
• Use flash on the dance floor. A short burst of flash freezes the people even when the shutter stays open longer for the room.
• Drag the shutter on purpose, for movement you want to show, and keep one sharp frame of the same moment.

Bursts are where culling comes in. CullTone groups each burst, marks motion blur with a plain reason and keeps the sharpest frame, so shooting three to get one doesn't cost you an evening (how the culling works).