Perfecting Focus and Lighting Enhancements in Photoshop CS4
Once you have your layer content in place, scaled, and masked as needed, it is sometimes necessary to create the illusion of continuous and smooth changes to focus levels, from the foreground to the background. This can be less an issue with commercial images such as advertisements, because they tend to blur the backgrounds and focus on the products or people in the foreground (in some cases there’s no discernable background detail at all).
Focus work is commonly required for composites that involve landscapes and other images with relatively long distances between the farthest discernable object in the frame and the viewer. Airport terminals and train platforms are also good examples of images that might require some real focus work on the individual layers placed within the scene (Figure 10.17).
Figure 10.17 For images with longer focus distances, pay attention to the details, and note where the sharpness starts to trail off. The amount of perceived blur visible in the immediately neighboring regions of the image dictates the sharpness of a given layer.
The trick is to set up each layer so that there is no break in the focus progression. For example, if your image is designed to quickly blur from the middle ground to the background, setting a sharpened subject in the background won’t help your cause. Even for images with a long depth of field, you still need to pay attention to where the details begin to blur slightly.
Lens Blur. The Lens Blur filter works on a simple principle (Figure 10.18). It uses masks (when enabled as a smart filter) or both masks and alpha channels (when applied to a standard layer) as a “sharpness map.” This map tells the filter which parts of a layer should receive the maximum blur (based on your settings), which parts to leave untouched, and any variations in between. As you might expect, anything that is masked with pure black will not be processed by the filter, while lighter and lighter shades of gray have more and more of the filter’s settings applied, until everything that is pure white uses the full effect.
Figure 10.18 The Lens Blur filter can apply precise amounts of simulated lens blur to your individual layers. Based on each layer’s placement in the scene and the relative sharpness of nearby objects, you can build a layer mask or alpha channel to tell Lens Blur where to make its changes.
The blur effect is defined by the Radius, Blade Curvature, and Rotation settings, though it’s never been entirely clear to us what the latter two settings do in terms of blur style. Experimentation is the only answer we’ve found that works every time. For this example we used the Gradient tool to draw a “protection mask” from the bottom-left half of the image toward the center of the shot, where it tapers off so that the full blur effect takes over at that point.
Keep in mind that the kind of blur you apply to your composite layers may change depending on the layer’s content. If your source image was shot with more detail than your scenic or base image, you may need to use the Surface Blur filter or Gaussian Blur filter, instead of Lens Blur.
Surface Blur. This filter allows you to remove some surface detail (and also camera noise in some cases!) without destroying high-contrast edge details. The Surface Blur filter can also help eliminate luminance noise in some cases. Very small amounts of surface blur can help soften the details of textures while preserving the larger view of your subject, as shown in Figure 10.19. Here we removed the raindrops from the surface of the vehicle, without blurring the edges of the rear door.
Figure 10.19 The Surface Blur filter can be useful when trying to soften the subject matter in a given layer so that it blends better with its surroundings, while not losing the higher-contrast edge and contour details.
Gaussian Blur. An old standby for many Photoshop artists, this filter applies a uniform blur across your image. This is the quicker solution when the entire subject is far enough away that edge detail would be lost or when depth of field would not have any noticeable effect. This is a good solution for background or foreground elements that are included for visual texture more than story telling (Figure 10.20).
Figure 10.20 The Gaussian Blur filter helps soften the entire content of a layer, and when needed, you can use the layer mask and the Gradient tool to show a gradual blurring or sharpening effect from “front to back” on a given object.
Here the basketball in the background takes on a completely different feel once blurred. The focus of the image now looks more realistic, as if the basketballs were photographed in the room (rather than having been placed there electronically). Obviously this is not a completed composite; however, it clearly demonstrates what a little bit of selective blurring can do in leading the perception of the viewer.
Motion Blur. One significant (and very common) challenge in compositing is producing the illusion of motion for objects that were not photographed while in motion. This is not a slam-dunk process by any means and usually requires some experimentation with the layer’s orientation and placement, as well as the amount and direction of blur being applied. Figure 10.21 illustrates how the Motion Blur filter gives the appearance of an object in motion. Here again we’ve given the basketball a completely different context, just by applying the blur.
Figure 10.21 The Motion Blur filter can do a serviceable—if not perfect—job of creating the illusion that the subject in your smart object layer is moving.
Whether the Motion Blur filter by itself resolves your particular situation will depend a lot on whether the intended effect is meant to be taken literally (in other words, you’re trying to fool the viewer into believing that the photographed object really was in motion at this location) or figuratively (such as an advertisement showing a bicycle “zooming” across a nondescript backdrop). Usually, a mix of overlapping layers works best (each layer having the same content but a different blur amount, and stacked on top of one another to give the impression of a single blurred object).
For some situations, a powerful 3D application like those mentioned in Chapter 9, “Creating 3D Content,” can actually produce a much more realistic motion blur, though it will take more time to find the right settings and values to create the perfect motion blur.