Certified Professional Photographer (CPP) Practice Exam

Which type of noise is caused by heat-generated electrons and accumulates over time?

1. Signal

2. White

3. Dark

4. Quantization

The correct answer is: Dark

Dark noise, also known as thermal noise or dark current, is generated by heat-generated electrons within the sensor of a digital camera or any electronic imaging device. As the sensor's temperature increases, some electrons gain energy and may contribute to the signal even in the absence of light. Dark noise tends to accumulate over time, especially during long exposures, leading to an increase in noise levels in the resulting image. This type of noise is particularly important for photographers to understand, as it can affect the clarity and quality of images captured under low-light conditions. Managing dark noise is often achieved through techniques like dark frame subtraction, where a reference image taken in complete darkness is used to correct the noise in the actual image. Other types of noise, such as signal noise, white noise, and quantization noise, have distinct characteristics and causes that differ from dark noise. Signal noise relates to fluctuations in the light signal, white noise encompasses random variations across the spectrum, and quantization noise arises from the digitization process, but none directly stem from heat-generated electrons accumulating with time in the same manner as dark noise.