Thursday, March 1, 2007

Say goodbye to noise with the Noise Reduction Filter in Photoshop CS2

PHOTOSHOP GURU

By Eddie Tapp

Creating a "noiseless" image is easier than you might think with the Photoshop CS Noise Reduction Filter. But you may wonder how and why your images became "noisy" in the first place.

Digital noise is usually created when an image is being shot in low light. Noise or grain is most noticeable in the darker colors or areas of an image and can often be found in just one of the colors.

Noise can be either chrominance (splotches of color, usually red or green) or luminance (specked pattern that looks like film grain). The Noise Reduction Filter does a good job of fixing both types of noise without abandoning the image's detail.

In short, the Noise Reduction Filter can reduce the grainy appearance of an image taken in low light and also remove a compression artifact from a JPEG.

To begin, open your image and create a duplicate layer. Always create a duplicate layer when manipulating an image. That way, you will have the "untouched" original to go back to if you're not satisfied with your adjustments.

Next, go to the Filters menu and select the Noise option. Select Reduce Noise and adjust the sliders until the noise is removed from your image. Feel free to play around with the sliders, but be watchful of creating too much blur.

Adjust the Reduce Color Noise slider to the right until most of the noise is removed. Then experiment with the other three sliders to add back detail and sharpness, as shown in Figure A. Use the Remove JPEG Artifact checkbox when the JPEG image you are adjusting has suffered degradation.

FIGURE A

First, adjust the sharpness. (click for larger image)

To further utilize this filter, check the Advanced option box and a per channel option will appear. This allows you to fix each color individually depending on which colors contain the most noise. To achieve the best results, use the two sliders below the color channel selector, as shown in Figure B.

FIGURE B

Next, try adjusting the individual color channels. (click for larger image)

If, when utilizing the Remove Noise Filter, you lessened another part of the image, simply use the history brush or a layer above the original layer to bring back those parts of the image that were better before. To do this, erase away with a soft-edged brush.

Details become less pronounced when an image contains noise. So by removing the noise, you can greatly improve the quality of your photograph. Unfortunately, you may not even realize that your digital camera is creating noise in your shot until you look at the image more closely.

So, it is important to be aware that when you are shooting in a low light situation, you will most likely have to rely on technological advances in Photoshop CS and the Noise Reduction Filter to tweak your image to perfection!

Eddie Tapp is an award-winning photographer, lecturer, consultant and author on digital imaging issues. Hailing from Atlanta, Georgia, as an award-winning photographer with over 20 years of experience in computer technology, Eddie has been actively involved in educating and consulting with corporations, studios and agencies in the applications of digital imaging workflow, color management, pre-press and digital photography globally through workshops, seminars, on-site consulting and training. In addition, he has a series of informative and interactive educational CD's produced by Software Cinema.