# calculate the 1/x format of shutter speed from given floating point value

How to calculate the x in 1/x format when all i got is decimal floating point representation of the shutter speed ( for example 0.0101316 and possibly other data in exif )?

## 1 Answer

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.

• The "traditional" speeds are just like the "traditional" apertures - They're rounded to the nearest (usually) round number. Aug 18, 2014 at 12:51
• can you recommend some "complete" shutter speed tables? I'm trying to make a software that has to show shutter speed and to make it usable for photographers i need to round to the nearest "common" shutter speed and i have a hard time coming up with a complete table because there are so many variables - exposure, stops etc. Aug 18, 2014 at 13:02
• what i get is the number i get from RAW image decoder with a bunch of other undrounded metadata like aperture (14.05),iso (200) etc. Aug 18, 2014 at 13:03