6 Replies Latest reply on May 5, 2017 9:31 AM by dragonfly57

    Radial Blur Bleeding Through Selection


      I am attempting to use radial blur on clouds to create a look of long exposure movement.  It is a cityscape image and the filter is being applied only to a sky selection (i.e. the lower half of the image, including the buildings, are excluded).  The problem I’m having upon running the filter is the buildings blur into the selected area as well.  The clouds are not right up against the selection.  I realize that I could mask and brush the unwanted blurring out, but it is extremely difficult to achieve a realistic outcome this way.  Is there a way to prevent the radial blur filter from allowing non-selected areas from bleeding into the selected area?

        • 1. Re: Radial Blur Bleeding Through Selection
          c.pfaffenbichler Level 9

          You could lift the selected area onto their own Layer (cml-J).

          • 2. Re: Radial Blur Bleeding Through Selection
            dragonfly57 Level 1

            I think I understand, so the "offending" pixels would not even exist (on the new layer) when the filter was run, correct?  I'll give it a try when I get home tonight.  Thanks.

            • 3. Re: Radial Blur Bleeding Through Selection
              SJRiegel Adobe Community Professional & MVP

              Also, lock transparency on the new layer so the blur doesn't bleed into the area over the buildings

              • 4. Re: Radial Blur Bleeding Through Selection
                dragonfly57 Level 1

                Good point, I'll do that too.  Thanks so much.

                • 5. Re: Radial Blur Bleeding Through Selection
                  Trevor.Dennis Adobe Community Professional

                  As a rule of thumb, I like to separate the components into their own layers.  You need to make the selection anyway, so make use of it.  This also allows you to reload the selection easily by Ctrl clicking the relevant layer.  However you do have options.

                  If you want to work on a single layer and blur a selection, then the lens filters do that without expanding outside the selection.  In this case Path Blur does the trick.  I can't show you the Layers panel in this screen shot, but I have Full Image copy selected, with and accurate selection of the sky.

                  That OKs as this.

                  In any composite situation, it usually works best to layer up and overlap so that the background extends under the composited layers.

                  So one of the buildings layers is moved to the top of the stack (turned off for now), and the sky layer selected.

                  The selection is expanded (Select > Modify > Expand)

                  I've then Ctrl Alt clicked on the buildings layer thumbnail to leave this band.  It is actually a good idea to expand this selection a few pixels again, because we are now going to use Content Aware Fill to expand the sky beneath the buildings, and you will get edge artefacts as things stand.  They would be easily fixable with the Healing brush, but why give yourself the trouble?

                  You now have an expanded sky that you can use Motion blur on or do what you like, and the building layer will cover any thinning of the border

                  This is what I got from motion blur, and it reveals that by CAF was not nearly big enough.  You could copy the layer a few times to firm it up, but it wouldn't fix it completely, so I should have been bolder with the CAF. 

                  I could have used CAF on all the transparent pixels.  The reason I didn't was this image was 6000 pixels wide, and my system was lagging.  I have downsized to 2000 pixels to do this.    You could certainly use motion or radial blur now.

                  But the bottom line is that the Lens Blur filters make selection edge bleed a non-problem, so why would you use anything else.


                  Spin Blur is a good case in point.  Do you remember all those problems you've had with radial blur on things like propellers and wheels.  I used to copy the area to a Smart Object layer so I could open in a new window and easily get the rotation point in the right place, but you still had problems with ellipses.  Spin blur fixes all the problems, and has some more cool tricks into the bargain.


                  This one by Steve Caplin is good.  Check out his How to Cheat at Photoshop site, and then on the Movies and Updates tabs.

                  • 6. Re: Radial Blur Bleeding Through Selection
                    dragonfly57 Level 1

                    Thank you for the great information. Question: Can you describe in a bit more detail as to how you are specifically using CAF in the above scenario?  Thanks so much.