Star Photography 500 Rule Calculator
When you shoot the night sky, the earth rotates and the stars slowly streak across a long exposure, so there is a maximum shutter time before pinpoint stars turn into short trails. The 500 rule gives a quick limit: divide 500 by your full frame equivalent focal length to get the longest exposure in seconds that keeps stars reasonably sharp. This calculator applies the 500 rule using your focal length and sensor crop factor, and it also computes the stricter 300 rule for demanding pixel level sharpness. Enter your focal length and pick a sensor, and you get the recommended maximum shutter time for a static tripod shot of the Milky Way or a starfield. A wider lens buys you a longer exposure and cleaner shadows. All calculation happens in your browser with nothing sent to a server.
How to use Star Photography 500 Rule Calculator
- Enter your focal length.
- Select your sensor size.
- Optionally enter aperture and pixel pitch for the NPF rule.
- Read the longest shutter speed before stars blur.
Frequently asked questions
What is the 500 rule?
It estimates the longest exposure before stars trail by dividing 500 by the full frame equivalent focal length, so a 20 mm lens allows about 25 seconds. The tool adjusts for your sensor size.
How does the NPF rule differ?
The NPF rule is stricter and factors in aperture and pixel size for pixel level sharpness, usually giving shorter times than the 500 rule for high resolution sensors.
Which rule should I use?
Use the 500 rule for a quick field estimate and the NPF rule when you need pinpoint stars on a detailed, high megapixel sensor.
What is Star Photography 500 Rule Calculator?
When you shoot the night sky, the earth rotates and the stars slowly streak across a long exposure, so there is a maximum shutter time before pinpoint stars turn into short trails. The 500 rule gives a quick limit: divide 500 by your full frame equivalent focal length to get the longest exposure in seconds that keeps stars reasonably sharp.
Is Star Photography 500 Rule Calculator free to use?
Yes. Star Photography 500 Rule Calculator is completely free, with no sign-up and no usage limits.
Does Star Photography 500 Rule Calculator work in a web browser?
Yes. Star Photography 500 Rule Calculator runs in any modern web browser. There is nothing to download or install.
Is my data private with Star Photography 500 Rule Calculator?
Yes. Star Photography 500 Rule Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.
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