Are you using movement to tell stories with your photos?  Motion can transport you into the photograph to truly bring it to life.  Using a slow shutter speed in your camera can help capture motion, but there are many times when that isn’t possible or practical.  But if you can’t capture it in camera, post-processing can often be used to add that emotional story-telling element.

Photoshop has long offered motion blur and radial blur filters, but they only creation motion in a perfect line or circle. They don’t let you create different amounts of blur to deal with depth in the image or a subject that may be speeding up or slowing down. And blurring in a straight line won’t even work if the subject is moving directly towards or away from the camera (which is part of the problem in my tutorial video below).  Fortunately, Photoshop now has the “Path Blur” tool (since Photoshop CC 2014). This incredible tool lets you create very sophisticated and realistic blur effects. I’ve posted the tutorial video below, as well as more information in my latest blog post, to help you master Path Blur.

In the video, I’ve also included an overview of the luminosity masks and exposure blending I used to prepare the image, how to blend the blurred layer into the image, and (most importantly) how to deal with artifacts at the edge of any blur. If you’re already familiar with those topics and just want to see how to use Path Blur, you may wish to skip to 3:42 in the video.  Note that even if you don’t have Photoshop CC, this tutorial still includes many great tips that are relevant to working with the older blur tools in Photoshop.

Steps to use the Path Blur filter:

1. Stamp all visible layers into a new layer on top by pressing <shift>-<alt/option>-<ctrl/cmd>-E.  You will create the blur on this separate layer so that you can later blend in motion just in the targeted areas of the photograph.
2. Convert the clone stamp to a smart object.  This will allow you to later revise the blur and to help correct some artifacts that may be created in the blurring process.
3. Click on Filter/Blur Gallery/Path Blur to start using the path blur tool.
   • Click and drag to draw blue arrows to define the path that your subject is moving in the image.
   • You may continue clicking and dragging to create as many blue arrows as you need.  This is helpful for multiple subjects.  It is also helpful for a subject that is coming towards or away from the camera (such as the escalator stairs and handrails in my tutorial video above).
   • Adjust the endpoint speeds to control how much blur is at the beginning and end of each blue line.  This value is specific to the endpoint that is currently active (click on an endpoint to make it active).
   • Adjust the speed setting to increase or decrease the amount of blur on all lines (ie, this is a global setting that is applied on top of the endpoint speeds).  It is important that this is set to a value above 0, or you won’t see any motion in the image.
   • You may wish to adjust the taper value.  This is also a global setting.  It controls how quickly the blur settings transition from one part of the image to another.  I often use a value in the middle of the slider (such as 20%).
   • Continue to tweak the various settings until you get the desired result.  It’s an iterative process, as the sliders interactive with each other.
4. Add a layer mask on the blurred layer to control which parts of your image are blurred (paint white on the mask) and which should be left alone (paint black on the mask).
5. Edit the smart object if you need to remove any blurring artifacts.  These are likely to occur at the edges of the blurred area when the nearby pixels look different from the blurred part of the image.
   • Use the clone stamp, healing brush, and content-aware fill to replace adjacent areas with content that looks similar to what you are blurring.
   • Don’t need to worry about being overly accurate, just getting “good enough” should make for a realistic blur.