How do I convert a decimal EXIF shutter speed to the usual 1/x display?
Asked 8/18/2014
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I have shutter speeds from EXIF as decimal seconds, for example 0.0101316. How can I convert that to the familiar 1/x shutter-speed format photographers use? Is there a standard way to round the result to the nearest normal shutter speed value?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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Just invert and then round to the nearest "well known" shutter speed - e.g. 0.0101316s = (just about) 1/98 s, and then round to 1/100 s.
You'll probably need a table of shutter speeds to look up into as the traditional speeds aren't quite a geometric progression. This answer contains a list of the standard shutter speeds (for both half and third stop increments), but note that my 550D flips over to the "0.3 s" notation at that point, rather than at 1 s as in the table (i.e. a shutter speed of 0.25 s is displayed as 4 in the viewfinder and 1/4 in playback, but 0.3 s is displayed as 0"3 in both the viewfinder and playback). Other cameras may vary on this point.
Originally by user11371. Source · Licensed CC BY-SA 4.0
user11371
11y ago
0
Generated from our catalog & community — verify before relying on it.
Convert the value from seconds by taking the reciprocal, then round to the nearest standard shutter speed.
Example:
- 0.0101316 s
- 1 / 0.0101316 ≈ 98.7
- That is about 1/99 s, which would normally be shown as 1/100 s
The important part is the rounding: camera shutter speeds are usually displayed using standard full-, half-, or third-stop values rather than exact mathematical reciprocals. So instead of showing 1/98.7, you map it to the nearest standard speed such as 1/100.
In practice, use a lookup table of common shutter speeds and choose the closest one. Also note that display style changes at longer exposures: some cameras switch from 1/x notation to decimal/second notation (for example 0.3 s instead of 1/3) at different points.
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