Motion Blur

Via Multiple Exposures and

NOT Via Long shutter speed and/or camera motion

We’ve all seen images that employ motion blur as a creativity technique. This is most often done by using a long exposure with a moving subject. We outdoor photographers do this regularly with water –

But – what do we do if the slowest shutter speed possible is too fast to give us the blur that we want (bright day and no neutral density filter)? All is not lost if you know how to do multiple exposures.  The  fundamentals for achieving the blur effect via multiple exposures are the same as doing a long time exposure – use a tripod, use a tripod, continue using the tripod. The only difference is that –

  • Instead of taking a single exposure of several seconds in duration,
  • You make multiple exposures (10 works well) at the slowest shutter speed available at the time.

When a single exposure at your slowest shutter speed won’t do the job, combining ten exposures can give you an image blur almost identical to what you’d have gotten with a single longer exposure.
Here’s a side-by-side example. Click to enlarge.

  • Left – 1/320 sec, water droplets
  • Center – 1/25 second, water streams
  • Right – same as center except repeat ten times to get a result nearly identical to what you’d see after a single 2-3 second exposure. I use a Nikon DSLR capable of in-camera multiple exposures and fire off ten exposures in about two seconds simply by holding down the shutter release in a burst frame mode – easy.

So there you have it. In certain situations you can use multiple exposures to give the same result as you would get via a single long exposure. When you consider that a Singh-Ray 77mm (Thin Mount) Vari-ND Variable Neutral Density Filter will set you back almost $400, this is a tip worth remembering.
For those of you who are technically inclined, take a look at “time averages vs. ensemble averages” for insight as to how/why this is so. Once an engineer always an engineer, I guess. There’s a big advantage in photography in using both sides of your brain when trying to make an image. 😉
Check the Table of Contents under Motion for more on this subject.

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