Night photography does not necessarily mean shooting in complete darkness. Low light, scattered light sources and mixed lights teach a photographer lessons in self-discipline. Night underlines a very significant difference between human eyes and camera sensors. As opposed to a human eye, a sensor is capable of accumulating light. However if there is no light, the physics is uncompromising, there will be no image. But if there are just a couple of photons roaming the scene they will be a delightful bite for a sensor and a sufficiently long exposure time will bring an image even with some additional bonuses.
Low light, an unusual ratio of highlights and shadows will force a photographer to think a bit more than before a common daylight shooting. The hunt for light will force you to use your gear to the fullest potential. Even if night photography is a game with colours and tones, there are several technical questions to be considered before one starts shooting in low light.
Night watchers – f/4.5, 1/30s, ISO 1250
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ISO - the sensitivity of the sensor should be kept as low as possible. Majority of night scenes will include dark areas, almost without a light signal, tending to produce digital noise. The higher the ISO, the higher the amount of noise may appear. On the other hand a low ISO will increase the demands for aperture and exposure time.
EXPOSURE TIME – long exposure times are the gate to night photography. Long exposures make use of the light-accumulative capabilities of the sensor and the resulting image may unveil colours and light effects which are hidden to the human eye. Long exposure times (minutes or even hours) call for using a sturdy tripod. Shooting with long exposure times one cannot rely on the built-in exposure meter, since it is limited to measure exposures with a shutter speed in the range of 30 seconds (or 60 seconds). If you exceed the value (using the BULB [B] mode) you cannot rely on its accuracy.
APERTURE – The aperture value influences some significant aspects of the image. Firstly it alters the depth of field. You should be aware of it, not because of the bokeh, but how it relates to the hyperfocal distance (i.e. higher aperture values will bring more of the image into sharp focus).
The aperture value will also alter the shape of bright spot light sources. At higher values the bright spots tend to produce rays around them. The number of rays is usually the same as the number of aperture blades on the lens. Sometimes the rays may disturb. You can get rid of them by lowering the aperture value (i.e. using a larger aperture).
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