Noise can creep into almost any image that is dark, like a nighttime shot, or one that has shadows. Noise can appear grainy in some areas and even have odd colors in the darkest areas. Pixel density on a camera sensor (many crowded into a small space), smaller sensor sizes such as in a cell phone, High ISO, and long exposure times can all contribute to unwanted grain in an image. How much is too much? Some like the artistic look of a little grain, especially in a black and white image. However, most would agree when one can not see important details in an image, it is too noisy.
Most photographers understand the importance of shooting a well exposed image, but sometimes shadows will appear in some images and nighttime shots as above can be tricky at best to get a good exposure. Some photographers will also sharpen certain images during the editing process, which may only worsen the appearance of noise.
Consider the Cityscape image above. Some may want to sharpen areas of detail such as the buildings. But, looking at the sky, there is no detail so it makes little sense to sharpen the entire image. There is a relatively easy way to limit what may be sharpened without necessarily resorting to a complex Photoshop selection or layer masks.
During the editing process, many people will start with Lightroom or Adobe Camera Raw. For what we area talking about in this post, the process will work exactly the same.
By using these quick and easy tips, you may find that you may not need to go much further in reducing noise in your image. One additional tip: