There are many reasons to explore blur in your images: remove distractions, direct attention, enhance space, modify mood and add interesting visual artifacts are a few among many. 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.
When it comes to postprocessing, you have options! Photoshop currently offers 14: Field Blur, Iris Blur, Tilt-Shift, Average, Blur, Blur More, Box Blur, Gaussian Blur, Lens Blur, Motion Blur, Radial Blur, Shape Blur, Smart Blur, Surface Blur—in order of appearance in the Filter > Blur drop-down menu. (If you want to extend your software palette even further, explore onOne Software’s FocalPoint.)
At first glance, the list is overwhelming. Where do you start? Get started with this quick survey of available options.
First, play process of elimination. Forget Blur and Blur More; they’re just fixed settings of Gaussian Blur. Put Average at the back of the back shelf; it averages all colors in an image into one, producing a flat field of color; it has extremely limited usefulness.
Second, start with the simple tools, grouping them by similar functions, and work your way up to the more complex ones.
Gaussian Blur is the ultra-simple workhorse everyone needs. It has one slider, Radius, which makes the effect stronger. It averages neighboring pixels; the higher the Radius, the farther its reach. At maximum, it can reduce an image to a flat field of color, a somewhat different color than Average. It’s extremely useful for modifying masks and special effects. It can be synthetically uniform and doesn’t convincingly simulate the more complex aspects of analog lens blurs or bokeh.
Many other blur filters are essentially Gaussian Blur with additional modifiers to alter the effect.
Box Blur produces a blur with a square shape. Rather than uniform, it’s linear, but not as gestural as Motion Blur and offering only 90º angles.
Shape Blur lets you choose from many different shapes, both geometric (these are the most useful—try circles, spirals, grids, triangles, etc.)—and iconic (they’re gimmicky—cats and dogs? Really? Why not?).
Surface Blur preserves contours. Like other blur filters, Radius controls the strength, but unlike others, Threshold controls the modifying effect. With Threshold set at the minimum of 2, no effect takes place. Even with Threshold at a maximum, the original image can be seen through a haze of color.
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.
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.
(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.