Theoretically, the Lab color space contains every color the human eye can see and the entire gamut of RGB and CMYK. It's an excellent color space for editing digital images, as it doesn't have some of the color limitations of the other color spaces. Lab color comes in quite handy when targeting noise, as it breaks down the image into specific criteria. The Lab color space is comprised of a luminosity channel and two chromatic ranges, called a and b. The luminosity channel represents the black and white information in your image, as well as the lightness. The a channel basically contains your greens through red, while the b channel ranges from blue to yellow. Since digital noise is contained in the chromatic channels, we can edit the a and b channels while keeping our black and white detail intact. Otherwise, we'd have to adjust either a single color channel (Red, Green, or Blue) or the entire image, making it harder to preserve image detail while reducing noise. Convert to Lab modeThe conversion to and from Lab mode is very clean. While going from RGB to CMYK can cause muddy colors, transforming your color space to Lab is quick and painless.
Adjust the channelsThe first step to fixing our noisy image is to view the specific Lab channel we're targeting.
Look unsharp!Now that we've blurred our a and b channels, it's a good idea to sharpen up the details in the Lightness channel to counteract the blur and keep the image looking crisp overall.
For our image, we set the Amount slider to 125%, the radius to 1.3, and the Threshold to 6 levels. Again, each image is different, so be flexible and try different combinations to get the best result. Our Problem and Solution images show RGB versions of an enlarged portion of our image before and after we applied our filters. We've reduced the noise without overly blurring the image and losing detail. By taking the time to adjust the image one channel at a time, we can keep the image looking good while minimizing the detrimental effects of noise. |