Noise in photography refers to the random variation of brightness or color information in images, which is usually an aspect of electronic noise. It is an undesirable by-product of image capture that obscures the desired information, and can range from almost imperceptible specks on a digital photograph taken in good light to optical and radioastronomical images that are almost entirely noise. There are two broad types of noise in photographs: shot noise and digital noise.

• Shot noise: This is randomness due to photons in the scene you are photographing, which are discreet and random. It appears when you photograph in low light conditions and use high ISO values.

• Digital noise: This is randomness caused by your camera sensor and internal electronics, which introduce imperfections to an image. It can be caused by a number of factors, including poor lighting conditions, high ISO settings, long exposure times, and heat.

Noise can be a frustrating part of photography, but it doesnt have to ruin your shots. By changing your camera settings and using noise-reducing software, you can reduce the amount of noise in your photographs. Some tips to avoid noise in your photographs are:

• Use a lower ISO setting if youre shooting in low-light conditions.
• Shoot in RAW format.
• Use a tripod or other stabilizing equipment to reduce camera shake.
• Avoid long exposure times.

To measure noise in an image, you can look for areas in the image where you have smooth transitions between colors, such as in the sky, and compare the standard deviation of the pixel values in that area to the average value of the smoothed image in the same area.