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.
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.
Yes. Star Photography 500 Rule Calculator is completely free, with no sign-up and no usage limits.
Yes. Star Photography 500 Rule Calculator runs in any modern web browser. There is nothing to download or install.
Yes. Star Photography 500 Rule Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.