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(you can also fade image adjustments and brush strokes, etc.). Choose Edit Fade Filter and experiment with different blending modes. The Fade command is almost like an adjustment layer feature, but without the versatility and ability to undo later. It makes use of the fact that the previous undo version of the image is stored in the undo buffer and allows you to calculate many different blends but without the timeconsuming expense of having to duplicate the layer first. Having said all that, the History feature offers an alternative approach whereby if you filter an image once, or more than once, you can return to the original state and paint in the future (filtered) state using the history brush or make a fill using the filtered history state (provided ‘Non-linear History’ has been enabled in the History panel options).

Enabling Lens Blur as a Smart Filter

Smart Filters are mainly intended for use with value-based filters only, such as the Add Noise or Unsharp Mask filter. They are not intended for use with filters such as Lens Blur because the Lens Blur filter can sometimes make calls to an external alpha channel, and if the selected alpha channel were to be deleted at some point, this would prevent the Smart Filter from working.

However, so long as you are aware of this limitation, it is still possible to enable Smart Filters to work with filters like Lens Blur. Go to the File Scripts menu in Photoshop CS5 and choose ‘Browse…’. This opens a system navigation window and from there you will want to use the following directory path: Adobe Photoshop CS5 folder/Scripting/ Sample Scripts/Javascript and select: EnableAllPluginsforSmartFilters.jsx. Once you have located this script, you can click ‘Load’ or double-click to run it, which will then pop the Script Alert dialog shown in Figure 10.7. If you wish to proceed, click ‘Yes’. The Lens Blur, as well as all other filters, will now be accessible for use as Smart Filters. If you want to turn off this behavior, run through the same above steps and click ‘No’ when the Script Alert dialog shows.

Figure 10.7 The Script alert dialog.

Lens Blur

If you want to make a photograph appear realistically out of focus, it is not just a matter of making the detail in the image more blurred. Consider for a moment how a camera lens focuses a viewed object to form an image that is made up of circular points on the film/sensor surface. When the radius of these points is very small, the image is considered sharp and when the radius is large, the image appears to be out of focus. It is also particularly noticeable the way bright highlights tend to blow out and how you can see the shape of the camera lens iris in the blurred highlight points. The Lens Blur filter has the potential to mimic the way a camera lens forms an optical image and the best way to understand how it works is to look at the shape of the bright lights in the nighttime scene in Figure 10.6, which shows the image before and after I applied the Lens Blur filter.

Figure 10.6 The best way to learn how to use the blur filters discussed here is to experiment with an image like the one shown here (which is available on the DVD). In this night-time scene there are lots of small points of light; you can use this image example to get a clear idea of how the Specular Highlights and Iris controls work, and observe how they affect the appearance of the blur in the photograph.

The main controls to concentrate on are the Radius slider, which controls the amount of blur that is applied to the image and the Specular Highlights slider, which controls how much the highlights blow out. To add more lens flare, increase the Brightness slightly and carefully lower the Threshold amount by one or two levels and check to see how this looks in the preview area. The Iris shape controls should be regarded as fine-tuning sliders that govern the shape of the out-of-focus points in the picture. You can select from a menu list of different iris shapes and then use the Blade Curvature and Rotation sliders to tweak the iris shape.