About Shutter Speed Calculator
Prevent star trails in night sky astrophotography using the Rule of 500, Rule of 400, and NPF rule, with motion freeze thresholds for action sports.
Key Capabilities & Features
- Astrophotography Rule of 500 and conservative Rule of 400 exposure time calculators
- NPF rule approximation for pinpoint star sharpness on high-resolution modern sensors
- Handheld reciprocal rule motion blur threshold calculation
- Motion freeze reference guide for waterfalls, walking subjects, sports, and flying birds
How to Use Shutter Speed Calculator
1
Enter Focal Length
Input your lens focal length in millimeters.
2
Select Sensor Size
Choose your camera sensor to account for crop factor.
3
Read Max Shutter Time
Review maximum exposure seconds before star trailing begins.
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100% client-side calculation. Your data stays private in your browser.
Frequently Asked Questions
What is the Rule of 500 in astrophotography?
The Rule of 500 states that maximum exposure time before noticeable star trailing equals 500 divided by the 35mm equivalent focal length of your lens.
Why use the NPF rule instead of Rule of 500?
High-megapixel sensors (33MP+) resolve tiny details that reveal star trailing earlier. The NPF rule provides tighter exposure bounds for pixel-level pinpoint sharpness.