This short tutorial demonstrates how to use the Photoshop Gaussian Blur filter to blur photo backgrounds. Blurring a photograph's background can help minimize distractions like onlookers at the zoo. If you want to hide people or objects in the background of a photograph it's pretty easy using blur filters described here, but you can also completely remove a photo background in this other tutorial.
The Photoshop Gaussian Blur filter allows you to blur an entire layer or a selection with the ability to adjust pixel radius. Filter > Blur > Gaussian Blur. I have found that you don't need to apply a very high pixel radius to obscure people in the background. In fact, a pixel radius of 1.5 will tend to be just fine when people are standing in the distance. But, you may need to adjust this number depending on how close people are standing. In this tutorial I am using a photograph I took of a giraffe at The Brevard Zoo in Florida.
Below is the original photo of a giraffe at the zoo with people in the background that I want to obscure using blur:
Important: Always make a backup of your original photos before modifying them. I typically modify a copy.
1. Use the Photoshop Polygonal Lasso Tool to outline the foreground object you want to isolate. In this case I am outlining the giraffe.
2. If you want a more precise outline I recommend using Photoshop's Zoom feature Cntrl and plus key (+) to zoom in. Cntrl and the minus key (-) will zoom out. See the example of the giraffe zoomed-in below:
3. Once you have traced your foreground subject, choose from the top menu Select > Inverse or Shift+Ctrl+I. This will select everything outside of the selected area (outside the giraffe).
4. From the top menu choose Filter > Blur > Gaussian Blur. Here you will be able to choose the amount of blur pixel radius. You can preview portions of your photograph by clicking and dragging the image inside the preview window. In the case of the giraffe I'm starting with a 1.5 pixel radius.
7. Click OK to apply. See examples below of gaussian blur applied at a 1.5 and 3.0 pixel radius.
Gaussian Blur at 1.5 pixel radius (To me this looks the most natural, but the child stroller near the giraffe's mouth is still a bit distracting)
Gaussian Blur at 3.0 pixel radius (Here you will see that more blur helps to hide the child's stroller a bit better)
Related Photoshop Tutorials:
How to Apply Photoshop Gaussian Blur to Photo Backgrounds | Removing a Zoo Photo's Background and Replacing it to Hide People | Photoshop CC Spin Blur Effect | Photoshop Clone Stamp Tool to Alter Landscape Photos | Best Ways to Cutout an Image