How to Reduce CMOS Noise

CMOS image processors have been criticized over their noise when compared to CCD sensors and Digital SLR cameras. So how do we reduce CMOS noise? Well, first we need to understand what noise is and how it is caused.

What Is Noise?

When we talk about noise in digital images, we are referring to small color specs that should not be there. For example, a photo shot in a low light situation might be covered in small white specs or a blue sky can have pink specs. Why does this happen? After all, digital images and audio are supposed to be superior to everything before it. The cause of the noise problem begins in the image sensor. This is where analog light is converted into digital photo electron signals. 

Heat and Noise

The first cause of a noise problem might be heat. Your digital image is comprised of photo electrons. Heat produces thermal electrons, which could contaminate an image with noise. The only way around this problem is to turn the camera off to let it cool down for a while.

ISO and Noise

Perhaps the biggest noise problem in a CMOS or any digital camera is the ISO. The ISO controls the sensor's sensitivity to light. A higher ISO level means that less light is needed for exposure. But, using the ISO to compensate for low light sacrifices your image to noise. Why? Well, it's because the high ISO amplifies the signal received by light photons. Unfortunately, it does not discriminate between electronic signals and also amplifies other background electrical signals, and that's what creates the noise.

How Manufacturers Are Reducing Noise

Digital SLR cameras don't suffer from noise problems like other cameras do. The reason is because they have a larger image sensor. The large image sensor allows larger pixels to be captured without overlapping on each other and causing noise. This does not mean SLRs are noise free. They still suffer from noise at high ISOs, they're just more resistant to it than other cameras. Quality with high ISOs varies from camera to camera.

Some manufacturers are building CMOS chips that incorporate algorithms to reduce noise. You can also buy noise reducing software to alter your photos after you shot them.

How You Can Reduce Noise

Exposure is dependent on ISO, shutter speed and the aperture. Leaving the ISO at the lowest setting possible will reduce the most noise. If you need to compensate for exposure, then do it first with the aperture because slowing your shutter speed may produce some noise too.


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