Digital noise usually occurs when taking low-light photos (such as night photos or indoor dark scenes) or when using very low shutter speeds or very high sensitivity modes.
When taking photos with a digital camera, an electronic sensor (also known as CCD) is made of very small pixels to measure light for each pixel. The result is a pixel matrix that represents the photograph.
As with all other electronic sensors, the CCD is not perfect and contains some noise (also known as the white noise for its random feature). In most lighting, light is significantly stronger than noise. However, in extreme scenes where light is too low, or when a high amplification is required, noise levels can become important and result in pixels that contain more noise data than real photo light data in photos. These pixels often appear as random spots or spots on the photo (for example, white spots randomly scattered on the photo).
Understanding digital noise in various scenes:
Low light (night photos or dark scenes): When the scene is dark, the amount of light measured by each pixel of the CCD is low. When the light intensity is too low, it may be very close to the noise level naturally found in the CCD. In such cases, some pixels may appear as noise because the noise level measured for them is significantly closer or higher than the actual light intensity.
Slow shutter speeds: More noise will come to the photo when the shutter is held open for a long time. The slow shutter speed turns into CCD, which integrates more light per pixel. The effect can be easily understood as “accumulating” CCD light in each pixel and measuring the total light during the shutter time. However, the CCD also "accumulates" noise. Therefore, some pixels will appear as noise in photographs with low shutter speeds, because the amount of integrated noise for these pixels is significantly close to or higher than the actual light being measured.
High sensitivity modes: High sensitivity in digital photography is implemented by mechanisms that result in amplification. CCD strengthens the measurements it takes. However, there is no way to amplify the real photo light falling on CCD pixels, instead noise and real light are both enhanced. As a result, the CCD becomes sensitive not only to light, but also to its own noise. Some pixels appear as noise when too much amplification is applied.
While it is not possible to completely prevent digital noise, there are several options that allow you to significantly reduce noise. There are two main parameters to play when taking pictures in low-light scenarios such as night photos: sensitivity and shutter speed. Increasing sensitivity creates more internal noise in the CCD, while slowing the shutter allows more noise to be integrated into the CCD. The amount of interference produced by both parameters is different. It is recommended that you set your camera to manual mode and play with several different sensitivity / shutter speed pairs to find the least interfering.
Some cameras have a built-in feature called “digital noise reduction”. Digital noise reduction is implemented by sophisticated software that can identify and remove noise pixels. For example, the software can identify noise pixels based on their randomness and the extreme intensity difference between them and their neighboring pixels. Noise removal can be accomplished by interpolation of a replacement pixel value based on neighboring pixels.
If you don't have a built-in noise reduction feature or it doesn't work properly, you can use PC-based software that removes digital noise. Many photo processing software includes a combination of automatic and manual digital noise canceling. Some software packages can be used to “average” several photos of the same object, thereby removing noise (due to the randomness of digital noise and the difference of noise pixels in each photo taken).
As a result, digital noise should be understood by an amateur or professional photographer. However, for most photographers, digital noise is not a practical problem, even in low light scenarios, usually digital noise is minimal and can be significantly reduced by turning on your camera's noise reduction feature. For professional photographers shooting in more challenging conditions, digital noise can be a real problem and can be handled using a combination of optimizing camera settings and interference with professional software.
No comments:
Post a Comment