The Rule of 500 is a formula used by photographers to calculate the (shutter speed) for capturing sharp, pinpoint stars without visible "star trails" caused by the Earth's rotation. The Formula:
While the basic rule applies to , modern digital sensors often require adjustments based on their specific hardware:
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Many modern photographers now use a "Rule of 400" or the more precise NPF Rule because high-megapixel sensors are more sensitive to tiny amounts of movement, making the Rule of 500 too "liberal" (resulting in slight blur). 3. Cultural Context: "1923" Episode 7
For cameras with APS-C sensors (like most entry-level DSLRs), you must first multiply the lens focal length by the camera's "crop factor" (usually 1.5x or 1.6x) before dividing.
It identifies the threshold where the movement of stars across the sky begins to blur into streaks rather than appearing as distinct dots in a long-exposure image. 2. Application and Adjustments
Shutter Speed (seconds)=500Focal Length of the LensShutter Speed (seconds) equals the fraction with numerator 500 and denominator Focal Length of the Lens end-fraction
Example: For a 24mm lens on a Nikon crop sensor (1.5x), the effective focal length is 36mm ( ). The rule would be
