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Gaussian Blur

Gaussian blur is a filter we can apply to our image to soften or blur it, as much or as little as we want.

The temptation can be to apply a lot of this kind of blur, however be very careful, as it does not follow the rules of depth of field and can look extremely unnatural. 

We have two ways we can apply Gaussian blur to our image, depending on what we’ve done to the image beforehand.

If we’ve done some copy/flip, Content Aware or similar we can either:

  • simply apply it to a non-smart object image layer, like our smooshed layer that we’ve been using in earlier lessons (note: duplicate your smooshed layer first!!). We can then mask it in.
    • The problem with this is that we can’t change the amount of blur, or remove it from the image. It’s applied to the pixels. As soon as we save and close Photoshop, or go further down the editing path, we will struggle to undo that effect if we change our minds. It is inflexible editing.
  • The other option is to make a duplicate of your smooshed layer, click Filter > Convert for Smart Filters. This will make it a Smart Object of sorts.
    • Now, when we apply the Gaussian blur filter to the layer, it is applied as a Smart Filter which means we can turn it off, edit it, make it stronger or weaker, etc. It is flexible editing.

If you do not have other image layers/a smooshed layer & are still working with your original:

  • make a new version of your smart object (Duplicate will work here, as if we go into Camera Raw Filter we want any changes to apply to the gaussian blur layer too)
  • go to Filters> Gaussian blur
  • Apply the blur.

Since you’re working on a Smart Object layer already, it will be applied as a Smart Filter, so the effect will be editable at any point. 

Professor Snoot's Tips

Using Gaussian blur will remove all the noise from that part of the image.

Hooray! Right?

Well… not necessarily. Depending on how much noise the rest of your original image has, your blurred area might stick out like a sore thumb, as it’s now unnaturally smooth and perfect.

To counter this, and to make sure your blurred area still fits the rest of your photo and looks natural, you might want to add some noise (I highly recommend it!). 

To do this, go back to Filter > Noise > Add Noise. You’ll probably only need between 1-3%, depending on how noisy your original image is.