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By Root 1976 0

feathered edge, the marching ants boundary will only represent the selected areas that have more than 50% opacity. Therefore, whenever you are working on a selection that has a soft edge you can use the Quick Mask mode to view the selection more accurately. To switch to Quick Mask mode from a selection, click the quick mask icon in the Tools panel (Figure 9.6) or use the keyboard shortcut to toggle back and forth between the Selection and Quick Mask modes. Whether you are working directly on an alpha channel or in Quick Mask mode, you can use any combination of Photoshop paint tools or image adjustments to modify the alpha channel or Quick Mask content. If you double-click the quick mask icon, this opens the Quick Mask Options shown in Figure 9.5 where you can alter the masking behavior and choose a different color from the Color Picker (this might be useful if the quick mask color is too similar to the colors in the image you are editing).

Figure 9.6 The Quick Mask mode button is in the Tools panel just below the foreground/background swatch colors. Shown here are the two modes: Selection mode (left) and Quick Mask mode (right). You can toggle between these two modes by clicking on this button. Double-click to open the Quick Mask Options shown in Figure 9.5.

Figure 9.4 The left half of the image shows a feathered selection and the right half shows the Quick Mask mode equivalent display.

Figure 9.5 The Quick Mask Options.

Creating an image selection

1.

I thought I would start with a straightforward example where I selected the elliptical marquee tool and dragged with the tool to define the shape of the mirrored sculpture. In order to preserve the selection I saved it as a new channel, which then appeared added to the Channels panel.

2.

Now I had created this selection I could use it to modify the image. Here, I loaded the selection, went to the Adjustments panel and added a new Curves adjustment using the settings shown here. I then went to the Masks panel, clicked on the Invert button to invert the selection and set the mask Feather to 2 pixels. This now applied the adjustment to the selected area outside of the mirrored sculpture.

Reloading selection shortcuts

To reload a selection from a saved mask channel, choose Select Load Selection… You can also -click a channel to load it as a selection. To select a specific channel and load it as a selection, use channel #channel # (where # equals the channel number).

One thing to be aware of here is that since CS4, the usual shortcut numbers have been shifted along by two. I have mentioned this a couple of times already, but it is worth repeating since this is something that is likely to catch people out who have been working with previous versions of Photoshop. Basically, is used (as before) to zoom the image to fit the screen and is now used to zoom to 100%. Where was once used to select the composite channel, the new shortcut is now . This means that you should use to select the Red channel, to select the Green channel, to select the Blue channel and subsequent numbers to select any additional mask/alpha channels that are stored in an image.

Modifying selections

You can modify the content of a selection using any of the modifier key methods discussed earlier in Chapter 1 (see pages 38–39). Just to recap, you hold down the key to add to a selection, hold down the key to subtract from a selection and hold down the AS keys to intersect a selection as you drag with a selection tool. The magic wand is a selection tool too, but here all you have to do is to click (not drag) with the magic wand, holding down the appropriate keys to add or subtract from a selection. Note that if you select either the lasso or one of the marquee tools, placing the cursor inside the selection and dragging moves the selection boundary position, but not the selection contents. With Photoshop CS4 and earlier versions this was only possible providing the target layer was visible. With Photoshop CS5 it does not matter whether the layer you have selected is visible