F STOP LIST FULL
F STOP LIST ISO

Note that these programming languages will also expect trig angles to be radians instead of degrees.

For example, the common approximation log 10(2) = 0.3 is valid in base 10, but in programming languages, log e(2) = 0.693147. Which works fine, no issue at all, except mixing with assumed constants from the wrong base won’t match.

Logarithms in programming languages (such as Excel, Javascript, Python, C, or Fortran) use log e instead of log 10.

It’s good for precision to use a couple of extra significant digits in the factors of exponents.

Fractional stops (like third, half, or tenth stops) simply add the fraction to the exponent of 2 or √2.

F STOP LIST ISO

Shutter speed and ISO numbers and ratios are Not reversed or squared, only f/stops Or n = 11.314/2.828 = 4 f/2.8 compared to f/11ĮV = log 10( n²) / log 10(2) = +4 EV differenceīut shutter speed and ISO are powers of 2, and run forward, so : N = 2.828/11.314 = 0.25 (with precise values of f/stops)ĮV = log 10( n²) / log 10(2) = -4 EV difference (log of fractions are negative) (f/stop ratios are reversed division due to f/stop numbers running backwards) To compare f/11 to f/2.8 (which we know f/11 is -4 EV from f/2.8) Which is what makes Guide Numbers so handy, automatically compensating for the Inverse Square Law. Guide Number calculation is an exception, when f/stop is not squared, because Inverse Square Law of distance is also a √2 factor. Value of f/stop NUMBERS are necessarily squared first in exposure calculations (because f/stop NUMBERS are powers of √2 but exposure stops are powers of 2).Īnd EV ratios of f/stop numbers are reversed and squared (because f/stop numbers increase exposure running in the opposite direction). Shutter speed 1 second and also fstop f/1 are stop number 0 because 2 0 is 1 (any number to power of 0 is 1). These sequential exponents of two are named to be Stop Number. Negative exponents compute fractions (less than 1), for example nominal shutter speed 1/30 second is the fifth sequential stop (counting from 1 second as stop number 0), so 2 -5 = 0.03125 = 1/32 second. Log₂(X) (below) is simply the exponential power of 2 that equals X (and we measure exposure in powers of 2, called EV).

Differences of exposure in EV units are also the sequential powers of 2 (i.e., 1 EV difference is a factor of 2x).

The precise goal of setting calculations are detailed below.

F STOP LIST FULL

ISO values are also powers of 2, but are modified to make ISO 100 become a full stop (and third stop numbers be relative to it). Actual camera design uses setting stops of exact powers of 2 for shutter speed values (1, 2, 4, 8, 16, 32, 64, 128, 256, etc), and powers of √2 for f/stop NUMBERS. For example, what we call 1/1000 second is actually binary 1/1024 second, which is unimportant in photography practice, but math needs the precise number.

The settings marked on cameras (shutter speed, f/stop, ISO) are Nominal values (approximate or rounded convention for human use), and are Not the exact Precise Goal Values that are used by the camera or in exposure calculations.

If these first basics are not clearly obvious, a longer version follows below. Several of the calculators here use these same basics.įirst, a Quick Summary of Exposure Computing I try to keep the math isolated here, but the math relates to several calculators on the local site pages, for example EV and EV Chart for page evchart.html are shown, and then also the charts of camera nominal and precise setting values for page fstop2.html. But if interested in computing with the camera exposure settings, here’s a few details which may be of interest. This page is Not likely of interest to those just wanting to take a picture. Camera Math of photography settings and EV A few math details about EV, f/stop, shutter speed, and ISO

F stop list