Regardless of how carefully you clean your scanner and your prints, some dust spots nearly always manage to escape the net. The following hack removes dust spots and small scratch marks without doing undue damage to the detail.
1. Duplicate the image layer.
2. Next, apply Filter^ Noise^ Dust & Scratches.
3. Set Threshold to 0 and then increase the Radius until you see the dust spots begin to disappear. You can make a judgment call by watching the document window or the proxy window. To compare a before and after preview, deselect the Preview checkbox to see a before display in the document window or, if using the proxy window, click in it and hold down the mouse button.
4. Increase the Threshold until you see the dust spots reappear and then decrease it steadily until there is a fine balance between the loss of fine detail and the dust and scratches.
5. Change the blend mode of this layer from Normal to Darken if the spots are white or to Lighten if they are black.
To refine the filter application further, play with the opacity or the Advanced Blending options to specify which pixels from the filtered layer affect the unfiltered layer below it. Learning to use the Blending Options feature (Layer ^ Layer Style ^ Blending Options) will enable you to do a lot of tasks that otherwise would require making complex selections! You might also, of course, apply a layer mask to the filtered layer and then mask any fine details that were lost, such as highlights, eyelashes, and so on.
There is one other way to use Dust & Scratches that's worth a mention here, though using a layer mask as described previously makes it rather redundant and not so versatile. After applying the filter, undo its effect (Edit ^ Step Backward). Next, in the History palette, click in the left column of the Dust & Scratches history state to set it as the source, select the History Brush tool, choose an appropriate brush tip, and then paint over the dust and scratches.
NOTE The Dust & Scratches filter is not really designed for best results as a global filter, although you can use it that way. Where possible, after duplicating the layer, use a feathered selection to isolate the affected area before invoking the filter; also, a small addition of noise or healing might be required after filtering but before deselecting.
In addition to the Dust & Scratches filter, you can also use the new Spot Healing Brush tool for minor healing, or its big brother the Healing Brush tool for serious healing. It's useful to know as many options and methods as possible because not all images require the same treatment.
To use the Spot Healing Brush tool (J), choose a brush tip slightly larger than the spot or scratch you want to heal and then lightly drag across it. That's about all there is to it!
In contrast to using the Healing Brush tool, you don't need to define a source; the tool samples automatically from around the brush tip. For that reason, you might need to increase or decrease the brush tip occasionally; otherwise, the healing may not match its immediate surroundings.
If the healing isn't to your satisfaction, you can try another blending mode from the options bar; for example, try switching between Normal and Replace blend modes (or one of the other modes). Replace tries to preserves noise, film grain, and texture at the edge of the healing strokes. Try also switching to a different source sampling type. There are two types to choose from: Proximity Match and Create Texture. The former is the default; the latter tries to create a texture from the pixels within the sampling area.
For healing large areas, the Healing Brush tool is preferable to the Spot Healing Brush tool. To use the tool, choose a brush tip slightly larger than the area you want to heal. Hold down Alt (Windows), Opt (Mac OS) and click to define a sample point from an area that has similar texture. Click or drag over the area to be healed. If the area being healed is small, the healing should take place almost instantaneously when you lift the mouse button. However, if you dragged across a large area and the file you are working on is huge or your resources are low, it might take time for the healing to take place. It's usually a good idea to heal in small strokes; that way, you can easily undo just the last stroke (see also the Tip on healing later in this section).
■ Blend Modes—As with the Spot Healing Brush tool, if the healing isn't to your satisfaction, you can try another blending mode; for example, try switching between Normal and Replace blend modes (or one of the other modes). Replace tries to preserve noise, film grain, and texture at the edge of the healing strokes.
■ Source—There are two sources to choose from: Sampled or Pattern. Sampled uses the texture, lighting, transparency, and shading from the sample point to heal the target healing area. Pattern uses a pattern, which you can select from the pop-up Pattern Picker by clicking the icon next to the option, to blend into the target healing area.
■ Aligned—Selecting this option sets the sampled source point so that it constantly realigns with the current position of the brush tip each time you click. When this option is not selected, the sampling is taken from the same source point each time you click.
■ Sample All Layers—This option, as the name implies, samples data from not just the current layer but also all layers, including the layers above the active layer.
■ Using Stylus Pressure—If you are using a stylus and tablet, you can vary the size of the stroke by applying pressure to the stylus. To enable the option, click the Brush icon in the options bar and from the pop-up palette choose Pen Pressure from the Size pop-up menu. You can also choose Stylus Wheel to base the deviation on the position of the pen thumbwheel. Furthermore, you can call up the pop-up palette at any time by right-clicking (Windows), ^-clicking (Mac OS) in document window. These stylus options are available for both the Spot Healing Brush and the Healing Brush tool.
TIP When healing, you are not confined to healing on the current layer. You can create a new layer and have the healed data placed for you on a new layer. This approach can give more options, such as blending modes, opacity control, and the option of turning off the layer visibility.
To avoid smudges and smears when healing close to the edge of the document bounds or high-contrast areas, make a selection around the area being healed and exclude the darker edges or change the brush tip to an ellipse and rotate it so that it avoids the dark edges. Smudges and smears occur when the tool tries to sample from outside the healing area in order to blend the sampled data. Creating a selection or changing the shape of the brush tip avoids sampling from the darker areas around the healing area.
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