Fix It In Photoshop | How To Create Perspective Motion Blur

David Coultham

When you sit in a car or a train, you will notice that objects closer to you look like they are moving quickly. Whereas, as objects get closer to the horizon, they appear to be moving much slower. We can replicate this same effect in Photoshop. Firstly though, we need to prepare the image so that the objects that we want to remain sharply in focus, are isolated from the background.

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Video | Perspective Motion Blur

STEP 1: Create two copies of the Background Layer by dragging the Background over the Create A New Layer icon at the bottom of the Layers Panel. You can also achieve this via the Application Bar and ‘Layer > Duplicate Layer’. I renamed the top Layer “Foreground Layer” and the middle Layer “Blur Layer” by double-clicking the text on each Layer.

STEP 2: With the “Foreground Layer” selected in the Layers Tab, make a selection of the subject or object you want to stay in focus using your favored method. I used the Pen Tool on this example because I wanted to make sure the shadow under the bus was captured; see  Making Precise Selections in Chapter 3.

STEP 3: Still working on the Foreground Layer, we are going to isolate the subject from the background. To keep our changes non-destructive, we will isolate the subject using a Mask. Click the Add Mask icon at the bottom of the Layers Tab (illustrated to the right). Doing the isolation this way means you can always go back later if you need to refine the selection. 

STEP 4: We need to re-load the Selection of the subject. To do this press and hold Command (on a Mac) or Control (on a PC) whilst clicking the Foreground Layer Mask. Next, we need to avoid ghosting from any of the edge pixels on the subject by expanding the selection. 20 to 30 pixels is normally enough, but this depends on the resolution of your original image. From the Application Bar, ‘Select > Modify >Expand’; then enter 20 pixels and press OK to commit the change. 

Your selection should now look something like this: whereby the selection is outside of the object.

STEP 5: Select the “Blur Layer” from the Layers Tab, head up to the Application Bar, and   ‘Edit > Content-Aware Fill’. This brings up the dedicated window for this function:

Don’t worry too much if the fill doesn’t look perfect. The background is going to be blurred anyway, so any inconsistencies will get masked anyway. Plus, the foreground subject will hide most of the fill areas. The default settings for Content-Aware Fill should be just fine, so go ahead and select OK from the bottom of the window to commit the change.

STEP 6: Before we apply any Filters, it is worthwhile turning the Layer into a Smart Object. This way, we can edit the Filter settings later on if we need to. Make sure you have the Blur Layer selected, and head up to the Application Bar and ‘Filters > Convert for Smart Filters’.

STEP 7: Photoshop still has a Selection loaded, therefore before applying any effects to our Blur Layer, we need to deselect the Selection, otherwise any effect will only occur inside the selected area. Press Command D (on a Mac) or Control D (on a PC). You can alternatively head to the Application Bar and ‘Select > Deselect’.

STEP 8: Still working on the Blur Layer, we are going to open the Path Blur interface. Head back up to the Application Bar, and ‘Filters > Blur Gallery > Path Blur’. You are presented with a dedicated Blur Tools window, and Photoshop places a motion Guide Pin onto your image. You can go ahead and delete this pin by selecting either of the endpoints and pressing Delete (on a Mac) or Backspace (on a PC).

STEP 9: Add Path Blur guides to your image along the perspective lines. You can add as many as you wish. At this stage, don’t worry about the blur effect looking correct, this is solved in the next step. 

It is useful when doing this step to zoom right out of your image so that you can drag the start points of the blur effect off of the image. The reason is that we are going to set the blur here to zero, as they represent the farthest points from the viewers’ perspective.

STEP 10: The next step in the process is to set the blur levels for the beginning and end points of the Perspective Paths Lines. Starting here with the beginning points highlighted in yellow, I set these to 0px blur. 

To do this, you first select one of the beginning points (noting you have to do this individually for each one). Then, head across the Blur Tools property panel and set the slider labeled ‘End Point’ to 0px.

You then repeat this process for the finish points of the Perspective Path Lines. This time though, you set the blur to a suitable value for your image. In this example, I used 190px for the Perspective Path Line that would be farthest away from the viewer, and for the ones closest I used 100px. Thereby replicating the effect that you would get in real life, where objects farther away appear to be less blurred.

NOTE: You can at any point adjust the perspective lines position, or indeed add or remove additional lines. Note also, that, you may notice a slight delay for Photoshop to apply the effect each time you make a settings adjustment. This is purely down to the processing power required to create these complex filter adjustments.

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