Those listed are full stops. Most cameras allow you to increment shutter speed and aperture in half-stops or one-third stops, and you can select intermediate values manually.
- If you have the camera set to half-stops, then you'll have 1/350 between 1/250 and 1/500.
- If you have 1/3 stop increments set, you'll have 1/320 and 1/400
To work these out, a full stop is double the light. A half stop then is the square root of 2 times, or 1.4 (so that if you go up a half stop, then another half stop, you multiply the 1.4 factor together, and 1.4 * 1.4 = 2, which is your full stop)
- So 250 times 1.4 = 350
- and 350 * 1.4 = 500
For 1/3 stops, it's the cube root of 2, or 1.26x
- 250 * 1.26 = 315 (rounded to 320)
- 315 * 1.26 = 396 (rounded to 400)
- 396 * 1.26 = 500
1/2 1/3<br/>
Stops Stops
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<kbd>250 </kbd><kbd>400 </kbd><br/>
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<kbd>125 </kbd><kbd>250 </kbd><br/>
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