Shutter Speed Calculator
Shutter Speed
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As Fraction
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Understanding the Exposure Triangle
The exposure triangle links shutter speed, aperture, and ISO. This calculator uses the APEX system: shutter speed t = N^2 / 2^EV, adjusted for ISO. EV (Exposure Value) represents scene brightness, with sunny days around EV 12-15 and dim indoors at EV 4-6.
Higher ISO values increase sensitivity, allowing faster shutter speeds. Doubling ISO is equivalent to one stop brighter. Wider apertures (smaller f-numbers) also admit more light.
Fast shutter speeds freeze action (1/1000s for sports), while slow speeds create motion blur. The reciprocal rule suggests using at least 1/focal-length for handheld shooting.
Frequently Asked Questions
What shutter speed freezes action?
Use 1/500s or faster for walking, 1/1000s for running or sports, 1/2000s or faster for birds in flight. For water, 1/500s freezes drops while 1/15s creates a smooth silky effect.
How does ISO affect shutter speed?
Doubling ISO lets you use a shutter speed twice as fast. Going from ISO 100 to 800 (3 stops) lets you go from 1/30s to 1/250s.
What EV values match common scenes?
EV 15: bright sun on sand/snow. EV 12-14: sunny to overcast. EV 8-10: bright indoors. EV 4-6: dim indoors.
What is the exposure triangle?
The relationship between aperture, shutter speed, and ISO. Changing one requires adjusting another for correct exposure.