Sharpening is almost part of any image retouching workflow. It can make great improvements on any picture if done right however, sharpening can easily be overdone and may lead to terrible results.
The most common way in Sharpening a photo is the Unsharp Mask Filter. I noticed that applying Unsharp Mask straight up increases the noise especially on the darker part of the image. What I do as an alternative is apply the sharpening in Lab Mode.
So why in Lab Mode, how is it different? In Lab (Lightness, A and B) Mode. I can isolate the Lightness Channel which contains only the luminance or light and dark tones of the image. Since there is no color data on this channel, we can avoid any color noise which causes noisy sharpening.
Here’s how we can sharpen an image in Lab Mode.
Step 1: Open your Image
Step 2: Change the image mode to Lab Color
You can change the image mode by going to Image > Mode > Lab Color

Step 3: Choose the Lightness Channel
To choose the Lightness Channel, go to the Channels Palette and click on Lightness. This should deselect your A and B channels and turn your image to black and white.

Step 4: Apply Unsharp Mask
While on the Lightness Channel, go to Filter > Sharpen > Unsharp Mask and put the necessary values. (I entered Amount: 50% Radius: 2px and Threshold: 1px. Every image requires different values, so you can enter the value that best suits the image)

Step 5: Convert the image back to RGB mode
Go back to Image > Mode > RGB Color
Let’s compare the images before and after sharpening.
Before:

After:


















