How many stops?

Calculate the number of stops difference between two exposure settings - enter the values in the upper and lower marked boxes. You can compare complete exposure settings of aperture and shutter speed, or shutter speed or aperture separately. (But obviously, if you fill in one aperture (for example), you have to fill in the other one as well, or the ratio can't be calculated.)

Shutter speed Aperture Exposure
First setting: f / By
Second setting: f /
Example: 1/125 (f/) 5.6
Exposure ratio upper:lower Whole stops
One-third stops
Precise stops

If the two settings are so close that rounding to the nearest whole stop or one-third stop would give a difference of zero, my prissier mathematical nature prevents me from letting this appear. A "smidgen" means less than one-sixth of a stop. Note that because the standard aperture values, f/2, f/2.8, f/4, etc. don't go exactly in a geometrical progression, many settings which are equivalent for practical purposes are actually out by a smidgen. E.g. 1/100 at f/2.8 is slightly more than 1/50 at f/4.

The basic comparison is done to three significant figures, which is vastly more than needed for practical purposes. This does mean that if you compare shutter speeds of 1000 and 1001 seconds, the program claims they are the same. This is not a bug!

Note that the units for shutter speed are seconds, not reciprocal seconds (i.e. "120" means 120 seconds, not 1/120).

Coming soon - what is an f-stop exactly, how do you calculate them, and why can't bank managers understand a geometric progression...