The Gaussian Blur filter is used to blur a picture or a selection. Go to Filters > Blur > Gaussian Blur to use the Gaussian Blur filter. The blur strength is affected by the radius. An example of the Gaussian Blur filter's dialogue window It includes a preview of an image with a blur radius of 5.0. Radius: Sets the distance in pixels that shapes each side of the blur. This value does not have any effect on monochrome images. Amount: Use this slider to change the amount of blurring. To lighten or darken an area, increase or decrease the amount of exposure used when taking the photo. Tool Size: Changes the size of the blur. Smaller values result in a sharper image with more detail, while larger values smooth out image details. Crop Mode: Selects the portion of the image that will be kept after blurring. Can be useful when you want to blur only a part of the image. Color: Displays the color profile for the selected layer. You can use this information to adjust the colors in your image before applying the Gaussian Blur filter. Profile: Displays a dialog box with several options for converting the selected image to the sRGB color space. See here for more information about sRGB. Gamma: Displays the gamma settings for the selected layer.