Exposure Stop Calculator
Compare shutter speed, aperture and ISO changes in photographic stops and calculate the net exposure difference between two settings.
Compare exposure settings in stops
Compare two shutter, aperture and ISO combinations and see the net exposure change.
How the Exposure Stop Calculator works
Exposure changes are conveniently expressed in stops because one stop represents a doubling or halving. For shutter time the stop change is log2(new time ÷ old time). Aperture uses two times log2(old f-number ÷ new f-number) because aperture area changes with the square of the f-number. ISO is compared as log2(new ISO ÷ old ISO).
How to use this exposure stop calculator
Enter the baseline exposure triangle and the new settings. Shutter time is entered in seconds, so 1/125 second is 0.008 and 1/1000 is 0.001. The calculator reports each component separately and then sums the stop changes. This makes it easy to verify whether one change was compensated by another.
How to interpret the result
A net result near zero means the two combinations are exposure-equivalent in the simple exposure model. A positive result is brighter and a negative result is darker. The separate component values are useful for understanding trade-offs: faster shutter reduces motion blur, wider aperture reduces depth of field, and higher ISO changes camera amplification/noise behavior.
Assumptions and limitations
The calculation does not know the scene luminance, flash contribution, lens transmission (T-stops), auto-ISO logic, highlight headroom or sensor response. Nominal shutter, f-number and ISO markings can also differ slightly from measured values. Treat stop arithmetic as a planning and comparison tool rather than a metrology result.
Practical example and workflow
Changing from 1/125 s at f/4 to 1/250 s at f/2.8 keeps ISO constant. The shutter loses about one stop while the wider aperture gains about one stop, producing a net result close to zero. That is a practical way to trade depth of field for motion control without changing nominal brightness.