# Fine-tune results with the Noise Brush

The Noise Brush allows you to selectively undo or fade the effects of noise removal. You simply brush on parts of the image where you want to reduce the amount of filtering. This is typically useful in cases where the filter has been too aggressive in areas of fine texture, which may be difficult to discern amid noise. Thanks to the Noise Brush, you are not left at the mercy of the noise reduction algorithm when you disagree with its decisions.

To use the brush, activate it by clicking on the Noise Brush selector button:

Now, paint with the mouse over the area that you want to undo or fade. If you change your mind, you can right-click or control-click to reverse the effect of the brush. Also, you can undo/redo individual brush strokes or all brush strokes using the corresponding buttons:

There are several controls that you can adjust to modify the behavior and size of the brush:

- Mode This controls the basic operation of the brush. In Undo mode, pixels in the filtered image are blended with pixels from the original image. In Redo mode, filtered pixels are blended back in. In either mode, you can reverse the operation of the brush by right-clicking or control-clicking.
- Channel You can apply the brush to the luminance channel, the color channels, or all channels of the image. Usually, you will get the best results by working in the luminance channel. Most detail is contained in the luminance channel, so you can fine-tune in this channel without reintroducing color noise (which is often more displeasing than luminance noise)..
- Edge type With a soft edge, the blending action of the brush is strongest in the center and weakens gradually toward the edge. With a hard edge, the blending action is uniform across the brush area.
- Radius This controls the size of the brush.
- Strength The strength slider controls the degree of blending in each stroke.

You can also adjust the size and strength of the brush by moving the corresponding sliders. The brush pattern is displayed when you make changes to the size or strength.

## Using the Noise Brush after batch processing

The Batch Processor allows you to filter many images automatically while you do other things. However, you can still use the Noise Brush on batch-processed images:

1. Open the filtered image that you want to touch-up with the Noise Brush.
2. Use the "Load undo buffer" command in the File menu to open the corresponding original image. This will load the unfiltered image into the undo buffer of the filtered image.
3. Now you can use the Noise Brush normally on the filtered image.