Step 4: Apply Unsharp Mask

Now we get to this seemingly misnamed filter — the Unsharp mask. If you are one who has not ever used the Unsharp Mask — because you always want to sharpen an image when you select the Sharpen menu, not un-sharpen your image — you are not the first to not use the most valuable tool for sharpening images! The name comes from a pre-digital darkroom technique where a blurry version of the contact negative was layered with the original contact negative. The result of combining these two "layers" was a pronounced edge contrast, making the image appear to be sharper. As the Unsharp Mask works in the same way, it is appropriately named and it is the best tool for the job — period!

■ Choose Filter >- Sharpen >- Unsharp Mask to get the Unsharp Mask dialog box shown in Figure 12.3. The Unsharp Mask has the following three settings:

■ Amount: This control determines how much the contrast increases in percentage terms ranging from 0% to 500%. This setting might also be considered as the intensity or effect strength setting.

■ Radius: Measured in pixels, Radius determines how wide the sharpening effect is. You can choose a setting between 0 pixels and 250 pixels and even in parts of a pixel, which is important when you are using values under 5 pixels, which you do most of the time.

■ Threshold: This control lets you set the starting point for when sharpening occurs. You can choose from 0 to 255 levels difference between two touching shades. When Threshold is set to 0, everything gets sharpened. When Threshold is set to 255, nothing gets sharpened. Using the optimal Threshold setting, you can usually prevent grain, scanner noise, or important image texture from being sharpened.

(150+ members) e-mail groups. As a member of his groups I have often benefited from his posts, enjoyed his humor, and continue to value his image sharp ening actions. As a full-time screenwriter and director, it amazes me that John always finds time to take photographs and actively share his passion for photography with those who join his groups or visit his Web site at www. pinkheadedbug.com.

The Unsharp Mask is actually creating a halo effect around edges. It creates a lighter shade on one side of what it thinks is an edge, and a darker shade on the other side, thereby creating the illusion of a sharp edge. Amount determines how bright the halo is, Radius determines how wide the halo is, and Threshold is the minimum shade difference required before a halo is created.

A good approach for getting optimal settings when working with high-resolution images is to set Amount to 175%, Radius to 2, and Threshold to 0. Most images require an Amount setting in the range of 150% to 200%. Generally, Radius values are less than 2.0 and each tenth of a pixel can be significant.

Setting Threshold to 0 means that every edge gets sharpened and for now that is okay as it is the easiest setting to adjust after the other two settings are determined. The tricky part is determining the right combination of Amount and Radius.

■ Set Amount to 175%, Radius to 2, and Threshold to 0.

■ Depending on the image, it may be better to define the edges with a narrower but brighter halo. Other images may look better with a wider, but less bright halo. See what you think looks best for this one by sliding the Amount to 200% or more and lower Radius to around 1.5 to 1.8. These settings make the rust chips look amazingly real, almost as if they are going to flake off your screen and into your keyboard.

■ As you change settings, click the Preview box in the Unsharp Mask dialog box to view the image with and without the sharpening effect. Also, click inside the Preview box to get the Hand tool. Click and drag the image around to view areas where you want to make sure the settings work.

■ As soon as you have a good combination of settings for Amount and Radius, look around the image for an area where there is fine texture, such as on the smooth part of the fender. You can now slowly slide the Threshold slider toward the right

until you remove the unwanted sharpening effect on the smoother areas.

■ For this image, I set Amount to 180%, Radius to 1.8, and Threshold to 4.

■ Click OK to apply the settings.

■ Because you did all the sharpening in the sharpened layer, you can now click the Hide Layer icon (the eye icon) in the left column of the Layers palette to view the difference between the original image and the sharpened image.

■ If you want to reduce the effects, choose Edit ^ Fade Unsharp Mask (Shift+Ctrl+F) to get the Fade dialog box shown in Figure 12.4. As you slide the Opacity slider toward the left, the sharpen effects fade. Besides using Normal, you should also try using the Luminosity blend mode.

■ Click Cancel to cancel the Fade settings.

At this point, the rusty old Dodge image looks much better than it did before the Unsharp Mask was applied. In this example, we have applied the Unsharp Mask to the entire image. Occasionally, you may work on an image where you don't want the entire image to be sharpened. Using the Quick Mask,

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layer mask, or a selection tool of your choice, you can easily select and remove or even change the opacity of the sharpened layer, leaving the unsharpened layer below as part of the viewable image.

Now that you have a good understanding of how to use the Unsharp Mask, here are two other approaches to sharpening an image.

SHARPENING INDIVIDUAL CHANNELS

Some lower-end scanners and digital cameras produce enough noise that it becomes difficult to sharpen an image without also sharpening and accentuating the unwanted noise, too. There are also images where it is hard to differentiate between important image texture or detail and the edges that you want to sharpen. In these and other cases, you want to take a look at each of the color channels to see if you can find one that holds most of the edges that you want to sharpen, but not much of the unnecessary detail. Typically, the lightest channel is the one that you want to sharpen, as it is also the one with the least amount of noise.

STEP 1: OPEN FILE AND DUPLICATE LAYER

■ Choose File >- Open (Ctrl+O) to display the Open dialog box. Double-click the \12 folder to open it and then click the dodge-before.tif file again to select it. Click Open to open the file.

■ Choose Layer >- Duplicate Layer to get the Duplicate Layer dialog box. Type Sharpened in the As box and then click OK.

STEP 2: EXAMINE THE RED, BLUE, AND GREEN CHANNELS

■ Your Channels palette should look like the one shown in Figure 12.5. If the Channels palette is not visible, choose Window >- Channels.

■ Click the Red channel (Ctrl+1), then the Green channel (Ctrl+2), and the Blue channel (Ctrl+3) to view each channel. Figures 12.6, Figure 12.7, and Figure 12.8 show each of the channels.

STEP 3: APPLY UNSHARP MASK

■ As the Red channel is the lightest channel, sharpen it as it has the least amount of detail that you don't want to sharpen.

■ Click the eye icon in the left column of the RGB channel so that you can see the effects of your settings in full color, but make sure to leave the Red channel as the active channel. The Channels palette should now look like the one shown in Figure 12.9.

■ Press the Spacebar to get the Hand tool and click and drag the image until you can see the

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Dodge logo, the rusty grill, and part of the left headlight if you have sufficient desktop. These are the key areas to watch as you apply effects.

■ Make sure the Red channel is highlighted and then choose Filter >- Sharpen ^ Unsharp Mask to get the Unsharp Mask dialog box.

■ Set Amount to 225%, Radius to 2.0, and Threshold to 0. This time, you can use a slightly higher setting for Amount, and you can use 0 for Threshold as the Red channel does not show all the detail that we saw earlier.

Some images have two channels that you need to sharpen. If so, beware that applying different settings can cause some rather unusual things to happen. My suggestion is to use the same settings if you are going to sharpen two channels. If you switch between the layers using the eye icon in the Layers palette, you will notice that sharpening just the red channel has caused a noticeable increase in red around some of the more defined edges — especially on the grill.

You can also have multiple views of the same document visible at once — one with only an individual channel visible and the other with the composite so you can see the effect changing one channel has on the entire image. Choose Window ^ Documents >-New Window.

USING FILTERS TO SELECT EDGES ONLY, AND THEN SHARPEN ONLY THE EDGES

As is true with many facets in life, the best way is often the most difficult or longest way. This axiom is true for sharpening images as well — that is if it weren't for John Brownlow! The longer way, and in most cases, the best way to sharpen an image is to first select all the edges that ought to be sharpened and then sharpen only those areas. While there are quite a few steps and many different approaches for this technique, John Brownlow has made it easy for all of us. He has created two action sets that automate several different sharpen techniques.

So, rather than go through all the steps, we just load John's actions, select one, and try it out.

STEP 1: OPEN FILE AND DUPLICATE LAYER

■ Choose File >- Open (Ctrl+O) to display the Open dialog box. Double-click the /12 folder to open it and then click the dodge-before.tif file again to select it. Click Open to open the file.

■ Choose Layer ^ Duplicate Layer to get the Duplicate Layer dialog box. Type Unsharpened in the As box and then click OK. This extra layer makes it easy for you to view before and after images.

■ Click in the Background layer to make it the active layer. Click the eye icon to hide the Unsharpened layer.

STEP 2: COPY ACTIONS INTO PHOTOSHOP FOLDER

■ As John's actions are so useful, I recommend that you copy them into the appropriate Photoshop folder so that you can easily access them any time you need to sharpen an image. Assuming you copied files from the companion CD-ROM as suggested in the Introduction, you find them in the \12 folder. The names of the action files are: Deadman's Custom Sharpen.atn and Deadman'sSharpeners.atn. Copy both of these files into the following Photoshop 7 folder:

C:\Program Files\Adobe\Photoshop 7.0\ Presets\Photoshop Actions

STEP 3: LOAD ACTIONS

■ To load the actions, click the menu button in the Actions palette. If the Actions palette is on your desktop, choose Window >- Actions. After clicking the menu button, you get a pop-up menu such as the one shown in Figure 12.10. If you copied the actions correctly, both of them are listed in the bottom part of the menu. Click Deadman's Custom Sharpen.atn to load it.

■ Click the Deadman's Custom Sharpen action set once to open it. Click the Deadman's Custom Sharpen! Action to open the action. The Actions palette should now look like the one shown in Figure 12.11.

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STEP 4: RUN ACTION

■ Before running the action, choose View >-Actual Pixels (Ctrl+Alt+0) so that you can see the results of the action on the full-size image.

■ Press the Spacebar to get the Hand tool. Click and drag so that you can see the Dodge logo and the front grill.

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■ To run the action, click the Play Selection icon at the bottom of the Actions palette. The action is well written with pop-up dialog boxes that make suggestions on the settings you should use. After making all the suggested settings, you have a sharpened image — it is that easy.

The image shown in Figure 12.2 is the result of applying Deadman's Super Sharpen action.

I suggest that you load the Deadman's Sharpeners.atn set as well. It includes four additional sharpening actions. My favorite for most images is the "Deadman's Super Sharpen" action. If you duplicate the background layer each time you try an action, or if you create a Snapshot in the History palette, you can easily compare the results of different actions and different settings. Experimenting with these actions and finding one that you can use on all of your digital images is well worth your time.

As sharpening is such an important topic for digital photographers, I suggest that you consult the following additional resources if you want to learn more about the topic.

The Web page, www.luminous-landscape. com/smart_sharp.htm, on Michael Reich-mann's Luminous Landscape Web site features "A Smart Sharpening Tutorial" written by John Brownlow.

Real World Photoshop 7 — Industrial-Strength Production Techniques, by David Blatner and Bruce Fraser (Peachpit Press), has devoted an entire chapter to the topic of sharpening. If you are serious about Photoshop, this is a must-have book for this and many other reasons.

Understanding Adobe Photoshop Features You Will Use

Understanding Adobe Photoshop Features You Will Use

Adobe Photoshop can be a complex tool only because you can do so much with it, however for in this video series, we're going to keep it as simple as possible. In fact, in this video you'll see an overview of the few tools and Adobe Photoshop features we will use. When you see this video, you'll see how you can do so much with so few features, but you'll learn how to use them in depth in the future videos.

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