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Night Photography Guide: Techniques
Sep 6 2011 5:00:00 pm EST
In the previous article of this series, I outlined desirable equipment for night photography. In this article, I explore some basic photographic techniques to achieve different effects.
Small Aperture, Low ISO, Long Exposure
A long exposure will soak up low light levels, creating daytime detail in an otherwise darkened environment. With a tripod, inanimate objects will appear crisp and clear while objects in motion will appear blurred or even invisible, if fast moving. Objects that are stationary for a portion of time, then moving, will appear transparent.
A small aperture, or large f-number will prevent too much light from entering, creating an overexposed image. It will also make a wider depth of field, bringing more of the background and foreground into focus.
A low ISO setting will also serve to prevent overexposure and minimize noise.
This technique is best performed with a tripod, a shutter cable, and lens hood. Vibration and light pollution are to be avoided during long exposures. The tripod keeps the camera stable, while the shutter cable prevents touching the camera, introducing hand vibrations. If your camera has a mirror up mode, it’s worth using, as the slapping of the mirror can introduce vibrations.
The lens hood blocks any light entering the periphery of the lens, creating a washed out effect. Likewise, if your SLR camera has a shutter on the viewfinder, it’s best to close it, preventing any light entering.
Any long exposure noise reduction settings should be activated. The long exposure will otherwise be grainy.
Large Aperture, High ISO, Short Exposure
Sometimes, you don’t want to use a tripod or flash. Instead, you want to take as much detail as quickly as possible in a low light environment. I recommend this approach when capturing fast moving subjects in a low light environment, where a flash might wash out the subject, or remove too much emphasis from the background.
I use this technique any time I can’t bounce a flash off a ceiling or wall, like when I am outside, or when there is detail beyond the flash range that I want to pick up.
Setting a wide aperture, like f/2.8 and lower, will soak up light quickly. The tradeoff is depth of field. At f/1.4, the depth of field is very shallow, and may make too much out of focus. However, the bokeh, or blurring effect of the background is considered desirable in many situations.
A high ISO will increase sensor sensitivity, while increasing noise. I recommend turning on any high ISO noise reduction, if your camera has it. I also recommend testing an acceptable limit for ISO. While some cameras can go over 10,000 ISO, the end result is perhaps too grainy for your preference.
If you set your ISO high enough and aperture low enough, you can capture your subject without a tripod. It’s always a fine balance to minimize graininess and produce just the right blur.
Flash Fired, Short Exposure
Most people are accustomed to this strategy. In essence, you rely upon the flash to illuminate your subject. The distance to your subject must be within your flash range. Everything beyond your flash range will be dark and subdued.
Typically, sharp contrast is your enemy when using a flash. A straight flash will often produce a harsh glare, sharp shadows, and an underexposed background.
If your flash can be adjusted, try bouncing it off a ceiling or wall. This will cast a more even tone, unless the wall is dark, in which case the subject will be underexposed.
In outdoor situations or when bouncing a flash is not desirable, a good diffuser will scatter the light, creating a softer, more even exposure.
Flash Fired, Long Exposure
In a sense, firing a flash during a long exposure is like taking two pictures at once. When the flash is fired, anything the flash illuminated is captured in vivid detail. For the remainder of the exposure, any inanimate foreground object is filled in greater detail while the background is also filled.
Any animate foreground object that moves after the flash is fired creates interesting effects. A person, for example, who walks out of the field of view will allow the background to fill in their flash impression, making them appear transparent when the exposure is completed.
Tripod vs Handheld
While a tripod is often desirable for a crisp, steady image, holding the camera can introduce some interesting blurring effects. For example, twisting the camera during exposure can produce a whirlpool effect, or panning from side to side can create horizontal banding.