# The Noise Brush page

The Noise Brush allows you to partially or completely protect regions of the image from being filtered, by simply painting with a brush-like tool. The effect is shown immediately in the Preview window. The Noise Brush can be useful for preserving hair or fine texture that is close to the noise threshold. Instead of spending a lot of time tweaking profiles and filter settings to optimize results, you can often get the results you want with a few quick strokes of the brush. Also, using the Noise Brush is generally easier and quicker than trying to do the same thing using Photoshop selections and layer masks.

The Noise Brush creates separate masks for the luminance and chroma components of the image. Most detail in an image is contained in the luminance channel, while the ugliest noise is often in the chroma channels. By applying the Noise Brush only to the luminance channel, you can preserve detail while eliminating color noise.

The Mode radio buttons control whether the brush increases or decreases the masking effect when it paints.

The Channel selector determines whether the brush is applied to luminance, chroma, or both mask components.

The Brush traits controls change the size, strength, and style of the brush. Tip: You can press the "." and "," keys to on the keyboard to increase or decrease the brush size.

The Erase mask button clears the filter mask for the entire image.

The mask created by the brush remains in effect until you erase it or quit the plug-in. So, you can go back and make further adjustments to the profile and filter sliders after using the brush. Also, as you scroll around in the preview window, the mask is scrolled along with it, so the preview always reflects how the final, filtered image will look.

You can view the filter mask by pressing and holding the View Filter Mask button . The luminance component of the mask is displayed in green, and the chroma component is displayed in red. Other colors like yellow denote areas where the two components overlap.

## The Noise Brush and batch processing (actions)

When you apply Noise Ninja to a batch of images via a Photoshop action, you don't have the opportunity to use the Noise Brush before the images are filtered. If you want to fine-tune the filtering results of individual images after a batch has been processed, there are a couple of possible solutions:

1) Use layer masks in Photoshop to blend the filtered and original image. Load the original image and the filtered image into separate layers of the same image document, with the filtered version in the top layer. Select the filtered layer, and choose "Layers->Add layer mask->Reveal all" in the Photoshop menu. Set the blending mode for the layer to Luminosity or Chroma depending on what components of the image you want to blend. Activate the brush tool, and select the layer mask of the filtered layer in the Layers palette. Using the brush, paint with black to blend in the original pixels, and paint with white to restore the filtered pixels.

2) You can use the "Load undo buffer" feature in the Standalone version of Noise Ninja. First, open the filtered image in the standalone application. Then use the "Load undo buffer" command in the File menu to open the original image. Now you can use the Noise Brush in the standalone application to tweak the filtered image. See the User Guide for the Standalone application for more information.