Noise in Digital Images

As cameras get better and better, they are offering higher and higher ISO settings. The Pentax K-1 has a high—not extended—ISO of  204,800. (You can read my review here.) At the same time, newer cameras are getting better and better as coping with digital noise with most not only having cleaner high ISO settings but also in-camera noise reduction, that works well depending on the cause of the noise and the camera used.

www.imaging-resource.comLike film grain, digital noise has many causes. Here are a few of the most common ones: Accumulative noise increases during long exposures and high ISO settings, in other words your typical night photography scenario. The noise varies with color and brightness and is different for every digital camera and is more obvious in underexposed areas where it’s spread across the frequency spectrum.

noise.japanAmplified noise is caused by high ISO speeds and is the digital equivalent of “pushing” film to achieve greater sensitivity. Dark noise is produced by heat from the camera’s sensor.  There;’s not much heat when you make one picture but during rapid shooting (I am guilt of this in the studio) or continuous mode there isn’t enough time between the captures to dissipate the heat generated. This heat is collected along with data from light passing through the lens. Random noise is created by fluctuations within the camera’s circuitry or even from electromagnetic waves outside the camera. Signal noise is caused by fluctuations in the distribution of how light strikes an image sensor.  There also other sources of external noise, including “pixel death” that is more pronounced at higher altitudes.

Here’s a few tips you can take to reduce noise before making a digital photograph:

  • 1) Avoid placing any external battery packs close to the camera. Some of these packs contain transformers that raise voltage levels to produce faster flash recycling but they also emit electromagnetic interference, which can result in banding effects.
  • 2) Avoid taking pictures close to strong sources of electromagnetic energy. I have been told that it’s quite common to see banding in images shot from the observation deck at the Empire State Building in NYC due to the presence of the antennas at the top of the building.

book

The book on low-light photography that Barry Staver and I wrote, Better Available Light Digital Photography, is out of print but you can buy used copies at really affordable prices on Amazon.com.

Author: Joe Farace

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