blur selected layer only with gradient

[bartonlew]

I've created a layer of the leftmost edge of this image which is outside and mostly behind the subject.  I want to blur this layer by using a gradient to create a gradual blur beginning at the bottom of the layer extending up the layer.  With the layer selected I went to Filter>Blur>Gaussian Blur and entered a value of 42.9.  I then selected Gradient and dragged up but got the result in the 2nd screenshot.  I assume there's some masking I need to be doing but I'm not sure what.  Can anyone help?  Thanks.

[Myra Ferguson · Accepted solution]

To apply a Gaussian Blur to a portion of the photo, do the following:

1.  Convert the Background layer to a Smart Object (with the layer selected, go to Filter > Convert for Smart Filters)
2. Apply the Gaussian Blur to the Smart Object (it will become a Smart Filter)
3. Select the Smart Filter Mask (it'll show up below the image thumbnail and the filter in the Layers panel
4. Select the Gradient Tool and draw your gradient on the mask (black conceals, white reveals)
5. You can also paint with the Brush tool on the mask or make selections and fill them in with a grayscale color (black, grays, and white)

[PECourtejoie]

Hello, a good method that is often used.

For a different result, that does vary the amount of blur, and not a varying opacity of a fixed amount of blur, 

I'd recommend to use the Blurt Gallery/Path blur, with one end point speed set to O px. 

This way, there is a real gradual amount of blur applied.

An alternative would be to use the Tilt-shift blur, with one side off the canvas.