Noise in low-light photography can be caused by high ISO settings, long exposure times, small sensor size, or a combination of these factors.

The primary purpose of noise reduction in low-light photography is to reduce the amount of visible noise in an image, which can make the image appear grainy or speckled.

Common techniques for noise reduction in low-light photography include using a noise reduction filter in post-processing, shooting at a lower ISO setting, and using a tripod to stabilize the camera.

Using a noise reduction filter in post-processing can reduce the sharpness of the image, increase the file size of the image, and take a long time to process.

Shooting at a lower ISO setting in low-light photography can reduce noise, improve image quality, and increase dynamic range.

Shooting at a lower ISO setting in low-light photography can lead to slower shutter speeds, increased risk of camera shake, and the need for a tripod.

Using a tripod in low-light photography can reduce camera shake, resulting in sharper images and increased depth of field.

Using a tripod in low-light photography can reduce mobility, increase setup time, and require additional equipment.

Common types of noise reduction filters used in post-processing include median filter, Gaussian blur filter, and bilateral filter.

Median filter preserves edges better, Gaussian blur filter produces smoother results, and median filter is more computationally expensive.

Bilateral filter preserves edges and textures, reduces noise effectively, and can be applied selectively.

Bilateral filter can be computationally expensive, may not be suitable for all types of noise, and requires careful parameter adjustment.

All of the provided options are good starting points for noise reduction in post-processing, depending on the specific image and the desired result.

The best way to determine the optimal noise reduction settings for a particular image is to experiment with different settings and compare the results, use a preset or automatic noise reduction tool, and consult a photography expert if needed.

Shooting in RAW format, using a lens with a wide aperture, and avoiding overexposing the image are all good practices for noise reduction in low-light photography.