Adobe Photoshop CS5 for Photographers - Martin Evening [121]
Radius and Detail grayscale preview
With the Radius and Detail sliders you are seeing a slightly different kind of preview when you hold down the key as you adjust these sliders. The grayscale preview you see here displays the sharpening effect in isolation, as if it were a sharpening effect applied on a separate layer. For those of you who are well acquainted with Photoshop layering techniques, imagine a layer in Photoshop that is filled with 50% gray and where the blend mode is set to ‘Overlay’. Such a layer has no effect on the layers beneath it until you start darkening or lightening parts of the layer. In Figure 4.5 you can see a mock-up of what the Detail grayscale preview is actually showing you. It effectively displays the sharpening effect in isolation as light and dark areas against a neutral, midtone gray.
Figure 4.5 This is a Photoshop simulation of what the grayscale Radius and Detail previews in Camera Raw are showing you. Imagine the sharpening effect being carried out on a separate layer above the background layer with the blend mode set to ‘Overlay’. When using the Overlay blend mode, a 50% gray has no effect on the layer below. Any gray tone that's darker than 50% darkens the layer below and any gray that's lighter than 50% lightens. If you consider a Camera Raw Detail panel grayscale preview in this context you will understand better that the low contrast preview image represents an isolated preview of the sharpening effect.
Masking slider
The Masking slider can be used to add a filter mask based on the edge details of an image. Essentially, this allows you to target the Camera Raw sharpening so that the sharpening adjustments are more targeted to the edges in the image rather than sharpening everything globally. As you adjust the Masking slider a mask is generated based on the image content, so that areas of the image where there are high contrast edges remain white (the sharpening effect is unmasked) and in the flatter areas of the image where there is smoother tone detail the mask is made black (the sharpening effect is masked). If you take the Masking slider all the way down to zero, no mask is generated and the sharpening effect is applied without any masking. As you increase the Masking, more areas become protected.
I like to think of the effect the Masking slider has on the Camera Raw sharpening as being like a layer mask that masks the layer that's applying the sharpening effect (see the Photoshop example in Figure 4.6). The calculations required to generate the mask are quite intensive, so if you are using a slow computer there may be a short delay as the mask preview is calculated, but on a modern, fast computer you should hardly notice any slow-down here.
Figure 4.6 Here is another simulation of what the Camera Raw Masking slider grayscale preview is showing you. As you hold down the key and drag the Masking slider you are effectively previewing a layer mask that masks the sharpening layer effect. In other words, the Masking slider preview shown opposite is kind of showing you a pixel layer mask preview of the masking effect.
I should also mention here how the Masking slider was inspired by a Photoshop edge masking technique that was originally devised by Bruce Fraser. You can read all about Bruce's Photoshop techniques for Input and Output sharpening in an updated version of his book, which is now coauthored with Jeff Schewe: Real World Image Sharpening with Adobe Photoshop, Camera Raw and Lightroom (2nd Edition). This book includes instructions on how