Adding noise to an image

When viewed at high magnification levels, most images obtained from digital cameras and scanners do not have perfectly uniform colors. Instead, the colors you see consist of pixels of many different colors. In image editing, "noise" refers to these random color variations in the pixels that make up an image.

Sometimes, such as when you are pasting part of one image into another, the difference in the amount of random color variation in the two images can stand out, preventing the images from blending together smoothly. In such a case, you can add noise to one or both images to create the illusion that both images come from the same source. You can also add noise to an image for artistic reasons, for instance, to simulate an old photograph or static on a television screen.

Original photograph; after adding noise

To add noise to an image:

1. Select the image.
2. Do one of the following to open the Add Noise dialog box:
   • In the Property inspector, click the Add Live Filters button, and select Noise > Add Noise from the Filters pop-up menu.
   • Select Filters > Noise > Add Noise.

   NOTE

   Applying a filter from the Filters menu is destructive; that is, it cannot be undone except when Edit > Undo is an option. To maintain the ability to adjust, turn off, or remove this filter, apply it as a Live Filter, as described in the first bulleted option in this step. For more information, see Using Live Filters.

3. Drag the Amount slider to set the amount of noise.

   Values range from 1 to 400. An increase in amount results in an image with more randomly placed pixels.

4. Select the Color check box to apply color noise. Leave the check box unchecked to apply monochrome noise only.
5. Click OK.