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Photographing Waterfalls: 1000-fold Exposure Range

When photographing a waterfall (or other forms of moving, turbulent water), the choice of shutter speed determines whether you get a stop-action view of every droplet in motion, or whether you get a smooth,  time-averaged view of the currents.  What is the best shutter speed to use with waterfalls?   I had the opportunity last year to do an experiment, an attempt to answer that question.  Of course, there is no single “best” shutter speed.  It is a mater of taste and creative vision.  But the experiment was useful nonetheless, since it resulted in a visual catalog of how a waterfall looks over a thousand-fold range of shutter speeds.

These pictures were all taken at Niagara Falls, with a Pentax K-7 DSLR, with a Tamron 28-75mm zoom lens at 28mm.   There are 21 shots, taken at 1/2 stop shutter speed increments, from 1/6000th of a second to 1/6th of a second.  In order to ensure the same exposures while varying the shutter speed I made compensatory adjustments to the aperture and the ISO settings.  (With a neutral density filter one could extend this to shutter speeds 2-stops slower.) Post-processing was limited to white balance and cropping.

So what did this tell me?  With shutter speed down to around 1/60th of a second, the waterfall looks pretty much the same.  From there down to 1/20th of a second you get gradual softening, and at the slowest shutter speeds you get effects ranging from painterly to otherworldly.  My favorite is 1/10th of a second.

I suspect the important factors here are:

  1. The speed of the water
  2. The distance of the camera from the water
  3. The focal length of the lens

These combine to determine, from the perspective of the camera sensor, the speed at which the water’s image moves, in pixels/second.  If the image is moving at 1 pixel/second, then shutter speeds faster than 1 second will show no blur.  But a shutter speed of 15 seconds will show a blur over 15 pixels.  I bet if I took the original 1/6000 second shot, loaded it in Photoshop and applied a motion blur until it looked as close as possible to the water in the 1/6 second exposure, I could work backwards to determine the speed of the water.

Shutter Speed Photograph
1/6000 second
1/4000 second
1/3000 second
1/2000 second
1/1500 second
1/1000 second
1/750 second
1/500 second
1/350 second
1/250 second
1/180 second
1/125 second
1/90 second
1/60 second
1/45 second
1/30 second
1/20 second
1/15 second
1/10 second
1/8 second
1/6 second
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