Photoshop Tip: Reducing Noise in High ISO Digital Picture

There are no photographers around who haven’t been in a low-light situation, but unable to use flash for any reason. With digital cameras the solution is easy – just boost the ISO value! Unfortunately, as ISO value gets higher, so does the digital noise. It shows in those weird-colored pixels, usually yellow, greenish or bluish in the shadow areas of the picture. Here is a quick tip how to reduce some of that noise using Lab Color mode in Photoshop:

- Open the noisy image in Photoshop, then select from the menu bar Image->Mode->Lab Color (this changes the color mode of your picture from RGB to Lab)
- Open Channels palette by selecting from menu bar Window->Channels (“a” and “b” channels contain color information, “lightness” contains the details)
- Select “a” channel
- While in “a” channel, select Filter->Blur->Gaussian Blur. Increase the pixel radius in the dialogue window until the details in the picture are completely blurred. Make sure you blurred all the rough edges and grain in the picture. You can easily go to radius of 4 pixels or more.
- Select “b” channel and repeat the Gaussian Blur filter
- Select “lightness” – if the edges are not so crisp, sharpen the picture a little using Unsharp Mask filter. Do not over-sharpen!
- Change the mode back to RGB (select Image->Mode->RGB Color

When working with files of the same size all the time, it may be useful to record this procedure as a Photoshop action.