The reciprocal rule says your shutter speed should be at least 1 divided by your lens focal length, so a 50mm lens needs roughly 1/50 second or faster for a sharp handheld photo. It guards against camera shake only, and it is a rough guide that you will often need to adjust.
How the Rule Works
Longer lenses magnify small hand movements as well as the scene, so they need faster shutter speeds. The rule gives you a simple number to begin with.
| Focal length | Minimum shutter speed |
|---|---|
| 24mm | 1/25 or faster |
| 50mm | 1/50 or faster |
| 100mm | 1/100 or faster |
| 200mm | 1/200 or faster |
| 400mm | 1/400 or faster |
In practice many people round up to the next common setting, such as 1/60 for a 50mm lens, to leave a safety margin.
Adjusting for Crop Sensors
On cameras with a smaller sensor, the image is cropped, so the effective view is tighter. A common habit is to multiply the focal length by the crop factor before applying the rule. A 50mm lens on a camera with a 1.5x crop factor then behaves like a 75mm lens, which calls for around 1/75 or faster.
When to Go Faster or Slower
- Go faster if you use a high resolution camera, because fine detail shows even small movement.
- Go faster if you are tired, cold or standing in an awkward position.
- Go slower if your lens or camera body has image stabilization, which many makers describe as helping by several stops. Results vary by person and by model.
- Go slower when you brace your elbows against your body or lean on a wall.
What the Rule Does Not Cover
The rule only addresses your own movement. If the subject is moving, such as a running child or a bird, you need a faster speed based on how quickly the subject moves. A shutter speed of roughly 1/500 and faster freezes most everyday movement, and fast action may need more.
How to Apply It in the Field
- Note the focal length you are using, or the zoom setting.
- Set the shutter speed to the matching fraction or a little faster.
- Raise ISO or open the aperture if the exposure becomes too dark.
- Take a frame, zoom in on the screen and check the sharpness.
- Adjust the speed until your own hands give consistent results.
FAQ
Does the rule work for video?
Not directly. Video shutter speed is usually tied to the frame rate, so stability comes from stabilization, a gimbal or a tripod instead.
Why is my photo blurry even at the recommended speed?
The cause may be subject movement, missed focus or very fine detail on a high resolution sensor. Try a faster speed and check your focus point.
The Short Version
Use 1 over the focal length as your minimum handheld shutter speed, round up when in doubt and account for crop factor. Stabilization helps, but moving subjects still need their own faster setting.
