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Old 25th July 2009, 08:15 PM
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Default Shutter speed in 1/3, 1/2.....

Hi,
In the book View Camera Technique from Leslie Stroebel 7th Edition on page 71, there's a formula to calculate the intermediate f-Numbers in 1/3, 1/2, 2/3 and full stop.

I was wondering if there is a formula for shutter speed in 1/3, 1/2, 2/3 and full stop.
Thank you
Jacques
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Old 26th July 2009, 09:03 PM
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The general formula is to multiply the original time by 2 to the power of the fraction. Divide instead of multiply to subtract a fraction of a stop:

x = y2^n where x is the new time, y is the starting time, n is the fraction (1/3, 1/2, 2/3 3/5, etc) and ^ means "to the power of".


Examples:

To find 8 seconds plus 1/4 of a stop, multiply 8 times 2^0.25 = 8 x 1.19 = 9.5 seconds.

To find 10 seconds plus 1/2 a stop: 10 x 2^0.5 = 10 x 1.41 = 14.1 seconds.

To find 32 seconds minus 1/6 of a stop: 32 / 2^0.167 = 10 / 1.12 = 28.6 seconds.
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Old 27th July 2009, 05:59 AM
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This stuff always baffles me. Maybe I should stick to guesswork and using a hat as a shutter!
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Old 27th July 2009, 06:15 PM
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Bob, thank you.
Jacques
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