Bridge Time

Coming up the trail from Kirby Cove, it was fully night. Not a pitch black night, because there was a sliver moon and light pollution from the bridge and city. But as dark as it was going to get.

Up on the fortifications of the Marin Headlands, I decided to see how long a time exposure I could make of the Golden Gate Bridge.

First I did some tests at 30 seconds to get the exposure right. My plan was to multiply out the exposure time once I had the right f/stop at this shutter speed (the maximum I can set on my Nikon D200 before going to Bulb). Based on what I was seeing in the LCD after exposure, 30 seconds and f/5.0 seemed about right.

Based on the 30 second exposure, I calculated that at f/22, the most stopped-down (smallest opening) of the lens I was using, 8 minutes would be about right.

Next I set the D200 to Bulb, which means the shutter will stay open as long as it is depressed. Since I really didn’t want to physically hold the shutter open for 8 minutes, I used the programmable Nikon MC-36 remote release.

It’s not too hard to set the MC-36 to whatever shutter time you’d like with the D200 on Bulb, although you need to remember to set Long to the time rather than Interval (it turns out that Interval means the time between multiple programmed exposures rather than the interval length of an exposure). Even though the MC-36 has a dim backlight, a headlamp really comes in handy for making settings in the dark.

I think the exposure as it came out is pretty interesting. A couple of things are worth noting. For some reason the camera’s EXIF data for the image shows an exposure of 479 seconds, one second shy of the 8 minutes I set using the control. Perhaps this is a round-off issue.

Also, you better have a great deal of patience for this kind of exposure, particualrly in cold and dark conditions. I’m using fast Sandisk Extreme III memory cards. Even so, each exposure took roughly 50% of the time the shutter speed time for writing to the card before I could use the camera again. This meant at least 12 minutes of standing around in the cold and dark for each exposure!

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