Moonlit Landscape Exposure Time Calculator

Moon percent illuminated:
Exposure time: seconds.


What's the use of this?

  • Planning night shoots. Do I really need to rent that f/1.4 lens, or I can I make do with a f/2.8 zoom?
  • Timelapse video scenes in which the moon rises partway through. How do you know your settings when the moon isn't around to take a meter reading?

I aim for this calculator to be accurate within 1/2 stop. It does not take into account:

  • light pollution, haze, or clouds. Most of the shoots that I used to calibrate this were done at high altitudes in the mountains.
  • very low moon elevations. If the moon is near the horizon, it won't illuminate as much.
  • personal exposure preferences. It's normal to underexpose by a stop or two at night.
  • vignetting. If you put your subject in the corner of the frame, it will likely be a couple stops darker.
  • transmission differences in lenses. If you're using a lens with a zillion elements, you might need to add 1/3 stop of exposure. This calculation assumes a lens with an average transmission. Most of the data that produced this was collected on a Rokinon 24mm f/1.4, Nikon 14-24, Tokina 11-16 v1, or Tokina 16-28. Also some lenses straight-up lie about their apertures (looking at you, Canon 85mm f/1.2L).
  • incorrectly-reported ISOs. Older Canon DSLRs were 2/3 of a stop more sensitive than they claimed. I don't know if there are current cameras that do this.

Other notes:

  • At small moon phases, the sky is the brightest area around. The f/2.8, ISO 6400, 1 minute exposure reported here will produce a fairly bright sky and a landscape that is 1-2 stops underexposed. You can probably keep this setting up until a 20% moon, at which point the landscape and sky will both be fairly bright.
  • For middle and large moon phases, this provides exposure settings that result in filling of the camera's dynamic range. White subjects will be nearly (but not quite) blown.
  • How this was produced: unfortunately, I did not take metered readings off an 18% gray card at every possible moon phase and use those to produce this. I found a formula for the light emitted by the moon as a function of phase. I then looked up my settings and moon phases for ~25 timelapse scenes. After compensating for varying apertures and ISOs, I multiplied the exposure time used for a particular scene by the lunar flux at that time. This produces a "correct exposure" number in arbitrary units. I took the median of these, and the "correct" night exposure settings for a given night are produced by dividing this number by the lunar flux of that night. Look at the source code of this page for the details. I've plotted my data points (and the theoretical model, which is what this calculator returns) below.


If you find this useful (or wrong and useless), let me know.