In digital imaging, noise refers to a coarse, pointillist pattern that is applied to create a graphic feel in an image. Noise is often used when an image is blurry to start with and resists sharpening with Photoshop's standard filters. In this case, you may like the effect created when you add noise and create a graphic look for the image, masking the lack of sharpness.
Open the File
Choose File, Open and select the file you want to modify.
Select the Noise Filter
Choose Filter, Noise, Add Noise to open the Add Noise dialog box.
Set the Amount
Move the Amount slider to control the amount of noise in the image. Observe the effect in both the preview window in the dialog box and in the original image area.
Set the Distribution
Select either the Uniform or Gaussian option to control how the effect is applied. The Gaussian option tends to mimic more closely the noise that appears on the emulsion of photographic film.
Select the Monochromatic Effect
Enable or disable the Monochromatic check box and observe the effect this option has on the image. By default, noise is added to an image using randomly colored pixels. These colors can be distracting in some images; the Monochromatic option adds noise using grayscale pixels.
Apply the Effect
Click OK to close the Add Noise dialog box and apply the effect.
Noise on a Layer
Instead of applying the Noise filter directly to the image, create a new layer filled with a color. Apply the Noise filter to the new layer and then adjust the opacity or blending modes to combine the color layer with the image layer. This approach lets you turn the effect on and off and apply it selectively using layer masks (see Part 11, Task 7, "How to Add a Layer Mask").