Today’s Post by Joe Farace
As DSLRs and mirrorless cameras get better and better, they are offering higher and higher ISO settings. The Pentax K-1 Mark II, for example, has a high—not extended—ISO of 819,200. That’s not a typo.
At the same time, newer cameras are getting better and better at coping with digital noise, with most not only having cleaner high ISO results but in-camera noise reduction that works well depending on the cause of the noise and the camera used.
Like film grain, digital noise has many causes. Here are a few of the most common ones:
Accumulative noise increases during long exposures with high ISO settings, in other words your typical night time photography scenario. The noise varies with color and brightness and is different for most digital cameras and is more obvious in underexposed areas where it’s spread across the frequency spectrum.
Amplified noise is caused by using 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 a single image but when shooting rapidly in continuous mode there isn’t enough time between captures to dissipate the heat generated. So the heat is collected along with the data from light passing through the lens and added to the image.
Random noise is created by fluctuations within the camera’s circuitry or even from electromagnetic waves (sunspots?) 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 pronounced at high altitudes.
Here’s a few tips you can take to reduce noise before making a digital photograph:
- Avoid placing any external battery packs close to the camera. Some packs contain transformers that raise voltage levels to produce faster flash recycling but they also emit electromagnetic interference, which can result in banding.
- Avoid taking pictures close to strong sources of electromagnetic energy. I’ve been told that it’s common to see banding in images that are shot from the observation deck at the Empire State Building in NYC due to the presence of all the antennas at the top of the building.
It’s World Book Day in the United Kingdom and Ireland that, since 1995 pursues placing a book in every child and young adult’s hand. Here in the USA you can help by picking up a copy of Better Available Light Digital Photography with new copies are available for $21.87 or used copies starting at giveaway prices—less than five bucks—from Amazon, as I write this. For some reason, the Kindle price is really high.