Friday, August 20, 2010

Bulb Based Exposure

The techniques for taking long exposures can vary depending on what you’re
photographing or the effect you want to create. For example I tell people when they are
photographing stars, whether it is star-trails or astro-photography, “the exposure is in the
aperture”. This is what I would call an “aperture based exposure”. More on that later.

Another type of long exposure photography that is popular involves using light-trails as
an image element. In this case I will be discussing using the light trails from cars and
trucks on our roadways.

If you want the vehicles light to “write out” a certain trail or pattern it is often difficult to
select the necessary shutter speed to match exactly what is needed. The world is a
dynamic place and the pace of things change. Maybe you would like to have the light-
trail extend throughout the frame or last for a portion of the exposure. In these instances
you may not be able to use a set shutter speed, personally these days I use bulb. So the
exposure constants are aperture and iso. I call this “Bulb Based Exposure”. Bulb based
exposure has been for me an evolution in my practice of long exposure photography.

Deconstructing "History ..."

Take for example this image, “History Repeats Itself”.

History Repeats Itself

I had two unknown time variables in regard to how long the shutter must be open. One, I
wanted to walk into the frame and using my flash manually fire it to illuminate each flag.
This meant 6 firings. Fortunately I was using a flash with a fresh set of nimh batteries and
was getting recharged in less than 4 seconds. The second variable, I wanted the lights from
the cars to travel throughout the frame, writing a serpentine reversed “s” in the frame.

Exposure 32 seconds, f22, iso50 with 6 manual flash firings at full power. In this case the
exposure would be to bottom out the iso, close down the aperture and open the shutter for
as long as you need to. It did take me 4 or 5 attempts to get this and bulb helped me get
what I wanted.

If you want to see “me” in the shot check out the image on my Flickr stream!

Please leave comments, be great to hear from you!

2 comments:

  1. Great explanation, not only of the technique used but of the composition. You should write a book!

    ReplyDelete

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