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PHOTOGRAPHY

Exposure Calculator

Find the longest shutter you can use before stars trail — for any brand of camera and lens. The NPF rule (accurate, default) and the 500 rule, side by side. Not in the list? Enter your kit by hand.

Longest shutter · before stars trail
15 s
f/2.8 · 14 mm
500 rule (500 ÷ focal): 30 s+

Pixel pitch 4.88 µm. · NPF is shorter than the 500 rule on high-resolution sensors (and more accurate).

Tips
  • Manual focus — set infinity on a bright star in live view.
  • Shoot RAW; white balance ~3500–4000 K (you can correct later).
  • Tripod + a 2 s shutter delay or a remote release.
  • Stopping down 1/3–1 stop from wide open cleans up stars in the corners.
● For ISO, white balance & a printable cheat sheet →
● Reverse · decode a frame

Already have a shot?

Paste a settings string — yours or one from the gallery — and read back what each value did, the aurora it suggests, and whether the stars would trail.