Adobe Photoshop CS Review

Lens Blur Filter

Because of their shorter focal length, digital compact cameras have a much larger depth of field (DOF) than conventional 35mm SLRs. That applies, to a lesser extent, also to digital SLRs which do not have full frame sensors. Although desirable in many instances (e.g. super tele), often a blur background or foreground is desirable to emphasize the subject. In the "pixelroom" a reduction of DOF can be achieved by creating a layer mask on a duplicate layer whereby black and white stand for "in focus" and "out of focus" respectively, and the amount of gray determines how far out of focus that area is. Applying a Gaussian Blur to the layer with the layer mask creates the effect of a reduced DOF. Instead of applying a simple Gaussian Blur, in Photoshop CS you now also have the Lens Blur filter available from the Filter -> Blur menu.

Lens Blur dialog box

This allows you to use the same layer mask (alpha channel) as an input for a more sophisticated and tunable model that allows for more realistic types of photographic lens blur.

Original image	Gaussian Blur applied	Lens Blur with Iris settings:  Shape: Hexagon  Radius: 20  Blade Curvature: 70  Rotation: 50	Lens Blur with Iris settings:  Shape: Pentagon  Radius: 30  Blade Curvature: 80  Rotation: 50

Obviously film grain does not depend on whether an area is in or out of focus. So the problem with the above filter is that the blurring of the layer with alpha channel smoothens out the noise, thus creating an artificial effect (because the noise in the Background layer remains unchanged). Therefore the Lens Blur filter also has a Noise slider which basically creates the same effect as Filter -> Noise -> Add Noise. I found that on the images I worked on, this noise was different from the noise in the Background layer. Applying an additional Gaussian Blur with a radius of 0.4 pixel to the layer with alpha channel solved the problem.

Photo Filter

Photo Filter dialog box

Filter Gallery

Just like the Filters Palette of Photoshop Elements 2, the Filter Gallery dialog box of Photoshop CS shows the effects of the filters in a graphical way and allows you to try out a variety of filters on the image without having to go back and forth to the Filter menu. However, unlike the Filters Palette in Photoshop Elements 2, not all filters of the Filter menu are available in the Photoshop CS Filter Gallery.

Filter Gallery dialog box

The key benefit of the new Filter Gallery dialog box is that it allows you to conveniently apply the same filter multiple times or combine the effect of multiple filters. Similar to what you can do with layers, you can rearrange the sequence of the filters by dragging them around and toggling their visibility. This makes it much easier to experiment with various filter combinations.