Creative Underwater Photography: Creating Motion Blur Against a Bright Blue Background

When taking photos underwater, you probably already know that you can use a slower shutter speed to make the background appear brighter. This article adds on that to show you a technique for capturing a sense of motion when photographing swimming fish. (Report by: Yasuaki Kagii)

EOS 5D Mark II/ EF100mm f/2.8L Macro IS USM/ FL: 100mm/ Manual exposure(f/9, 1/15 sec)/ ISO 200/ WB: Auto

When taking underwater photos, I usually tend not to vary my ISO speed or flash output, and also use a fixed aperture setting. For example, if my intent is to achieve a photo that resembles a documentary drawing in a field guide, I usually stick to f/7.1, whereas when I want a softer effect, I often fix my f-number as f/5. In other words, when I want to change how my photos look, I vary my shutter speed.

For the photo above, there was no direct sunlight in my shooting location. As there were shadows in some areas, I decided to use a slow synch flash to bring out the sense of motion. I wanted the shapes of the fish to be clearly visible, and to achieve that effect, I directed my flash onto the fish, set my aperture at a narrower f/9 and the shutter speed to 1/15 second, and then panned the camera to the right as I released the shutter. This created a motion blur effect in the background that suggested speed in the swimming fish.

Also read: How to Slow Sync with a Built-In Flash

Using a slow shutter speed also helps to brighten the background

In underwater photography, your choice of shutter speed can affect how the background colours appear in the actual photo. A fast shutter speed results in a darker background, as in the example below taken at 1/100 seconds. In the example at the top, the shutter speed was a relatively slower 1/15 seconds, which allowed more light to reach the sensor resulting in a final image where the water appeared bright blue.  

You may be interested in: 4 Keys to Capturing Lovely Underwater Photos in Shades of Aquamarine 

EOS 5D Mark II/ EF100mm f/2.8L Macro IS USM/ FL: 100mm/ Manual exposure(f/9, 1/100 sec)/ ISO 200/ WB: Auto

1/100 second

Using a shutter speed of 1/100 second results in a darker background. A fast shutter speed like this also “freezes” the swimming fish in place, suggesting stillness instead of motion.

For more tips on external flash photography, check out:
In Focus: The Basics of External Flash Photography

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