DPP Home Technique (R)evolution Photoshop Blur Filters, Part I

Tuesday, November 5, 2013

Photoshop Blur Filters, Part I

Take complete control of the blur effect in your images in the computer

This Article Features Photo Zoom

7) Motion Blur
Blurs That Simulate Analog Effects
Motion Blur's two sliders produce a linear blur that spreads in two directions to a distance and at an angle of your choosing. The Motion Blur filter can convincingly simulate simple linear motion blurs of either subject or camera made during exposure; slightly more complex motions can be simulated by adding the Liquify filter into the mix afterwards. But no filter will produce the effects of extremely complex motions during exposure or reveal the background behind moving subjects—a second exposure is required.

Radial Blur offers two other directions for motion blur effects: Zoom and Spin. Radial Blur's preview isn't dynamic, so you have to apply the filter to see the effect of different settings, which often leads to many rounds of undoing and reapplying. You position the center of the effect in the dialog box to get closer to your target. Or, you can draw two guides to create a crosshair pinpointing a location and then expand Canvas Size to reposition the midpoint of a file on the crosshairs and thus the position of the effect, and after applying the filter, crop the added canvas.
Blur can be controlled at the point of capture and in postprocessing. Thoroughly understanding your postprocessing options will help you make choices about when and how to control blur in your images before, during and after exposure.
Just as Gaussian Blur is the go-to simple synthetic blur you use again and again, Lens Blur is the go-to sophisticated analog simulation blur you'll use most. Lens Blur is the filter that most convincingly simulates lens bokeh (the quality rather than the amount of blur). The differences between it and other filters are best seen in small patches or points of light. Where other blur filters might reduce these points of light uniformly or remove them altogether, Lens Blur transforms them into semitransparent shapes, mimicking the look and feel of effects produced by a camera lens iris. Lens Blur offers six Shapes to choose from: Triangle, Square, Pentagon, Hexagon, Septagon and Octagon.

8) Shape Blur
You can control the amount of blur with Radius, further spread and smooth the effect with Blade Curvature, and turn the angle of the shape with Rotation. You can control the Brightness of Specular Highlights and the Threshold at which they appear. Adding simple Noise (Uniform or Gaussian) in this interface adds extra convenience should you want to compensate for the super-smooth, sometimes synthetic-looking effects digital blurring can produce. For more control over noise, use another filter like Grain or a plug-in like RealGrain on a separate layer. (See my previous DPP column.)

In addition, you can apply the filter selectively by loading a mask channel or Depth Map and use the Blur Focal Distance slider to control the amount of the effect. Complicated at first glance, you'll find you most frequently use the four controls of the Iris section and two controls of the Specular Highlights section. This one is worth mastering.

9) Smart Blur
(Note that Lens Blur isn't available as a Smart Filter because it can make calls to an alpha channel, which, if deleted, would prevent the filter from working. You can enable Lens Blur to work as a Smart Filter by visiting the Adobe website and downloading the Enable All Plugins script from the Adobe website (www.adobe.com). Place the script in the folder Presets > Scripts. Then go to File > Scripts > Browse, and Load the script.)

In Part 2 of this series in the January/February 2014 issue of DPP, we'll cover Blur Tools, Smart Filters and more.

John Paul Caponigro, author of Adobe Photoshop Master Class and the DVD series R/Evolution, is an internationally renowned fine artist, an authority on digital printing, and a respected lecturer and workshop leader. Get access to a wealth of online resources with his free ennews Insights at www.johnpaulcaponigro.com.


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