Wordy Wednesday #102: “Cruise Night in Escondido”
More and more cameras are offering higher ISO setting and along with the good news comes the bad. Noise in digital photographs is the visual equivalent of static in radio signals and most digital cameras add some noise to images. Digital noise has many causes: Dark noise is produced by heat from the camera’s sensor during capture. The dark current produced is collected along with the light passing through the lens. Random noise is created by fluctuations within the camera’s circuitry or electromagnetic waves outside the camera.
Signal noise is caused by fluctuations in the distribution of how light strikes a sensor. You’ll sometimes hear the term signal-to-noise-ratio ratio, which is a measure of signal strength relative to background noise. Amplified noise is caused by high ISO speeds and is the digital equivalent of “pushing” film to achieve greater light sensitivity. Then there’s accumulative noise, which is caused by using slow shutter speeds.
Some nighttime photography involves trial and error. While photographing cruise night on the main drag on Escondido California, I kicked the EOS 50D’s ISO up to 800, set the camera in Aperture Priority mode just lived with a 0.3 second exposure because I was more concerned about the mood than capturing these street rods in sharp focus. I experimented with Exposure Compensation and increased this shot by one-thirds stop but it was still slightly underexposed.