Dragging the Shutter
I shot a wedding last weekend. It was an exposure nightmare. The wedding was held at Alderbrook Resort out on Hood Canal in a small meeting room on the front side of the building. A nice enough setting, but one definitely not made for wedding photographers. The room had a fire-place set between several large windows. The bride, groom, and minister stood in front of the fireplace. The curtains were pulled shut on the windows, which was fine because any views out those windows would have been totally blown out. However, with the curtains shut, the room was dark – the lighting provided a nice mood, but not much else. Obviously I had to use a flash.
I wanted to preserve some room detail with the ambient room light, not light up everything with the flash (while simultaneously blowing the bride’s dress out into an overexposed white blob). This called for using a slow enough shutter speed, coupled with a wide aperture, to allow for some of the ambient light to show. I ended up using shutter speeds from 1/30th to 1/50th of a second, with an aperture of f/4 to f/5.6 (yes, I could have opened up the lens a bit more, but I was trying to keep a little depth of field). After the ceremony, we took portrait shots around the hotel. The lighting was not much better in most locations. Again, I wanted to save some ambient light in the background – long shutter speeds were needed.
Now there is a standard rule of thumb in photography that says while hand holding a camera, you shouldn’t have a shutter speed slower than the reciprocal of the focal length of the lens. Here’s an example for the math impaired – say you are using a lens with a focal length of 100 mm, than your shutter speed should be no less than 1/100 of a second. However, I must be a pretty shaky guy, I find things tend to get a bit blurry whenever I go below 1/60 of a second, even with small focal lengths.
The rule-of-thumb, of course, assumes a non-stabilized lens, like the one I was using. I was using my 24-70mm zoom lens for most the shots. I was mostly using it at its upper end, say 40 to 70mm. Now, my camera has a 1.6 crop factor, so it was as if I was using the lens at 64 to 112mm. So, I should be using shutter speeds between 1/60 and 1/120 of a second, yet here I was shooting down as low as 1/30th.
So, at those low speeds, how does a shaky cameraman like me keep the subjects from blurring? The flash does it – freezes everything in its path. Not just camera shake, but moving subjects as well. Electronic camera flash units fire at about 1/1000 of a second. A burst of light so fast it freezes even my worst camera shake – not to mention a nervous bride (not that she was nervous in this case, but you get the idea). So this quick blast of light from you flash unit allows for longer shutter speeds to let in more ambient light. The technique is called “dragging the shutter” (which I think sounds cool) or slow shutter sync (which does not). When using this technique, you probably want to set the camera to rear- or second-curtain synchronization. (What is that you ask – that my friend is the subject of another blog; stay tuned!)
So I was dragging the shutter all day long, all over that hotel; and I was happy with the results. Hopefully the bride will be too.