Adobe Photoshop Print Production Tips
Excerpted from Real World Print Production with Adobe Creative Cloud (Peachpit Press)
By Claudia McCue
Countless books and Web sites are devoted to using Adobe Photoshop for the entire spectrum of skill levels, from beginner to Master of the Pixel-Based Universe. We’re assuming you understand the basics of Photoshop, so you won’t find any basic how-to instructions here. Nor is this a Hot Tips & Tricks compendium. What you will find are tips to help you create print-ready files and some heads-up warnings regarding tricks that the software can play on you. Because Photoshop is used for a wide variety of purposes, from Web to print and video, it provides multiple methods for accomplishing what you want to do to an image. The method that might be ideal for Web is not necessarily appropriate to use on an image intended for print.
Off to a Good Start
Before you start slinging pixels around, do a bit of planning. You may just be stuck with a low-quality supplied image, with no control over how it began life. In that case, you may have to make some compromises for print.
Know the Fate of the Image
Before you photograph a subject with a digital camera, or scan a piece of artwork, it’s helpful to know how the image will ultimately be used. Consider some important issues:
- At what scale factor will the image be used? If possible, shoot or scan the image to the final size rather than scaling the image in Photoshop or a page-layout application.
- Will the image be used at multiple sizes? If the scale factors are fairly close (for example, the image is being used at 8-by-10 inches and at 6.5-by-8 inches), shoot for the larger size and just use scaling tools in the page-layout application for the smaller size. But if there is a substantial difference in scale factors—an image used at 8-by-10 inches and at 2.5-by-3 inches, for example—it’s worth making a separate image for each use. Create the image for the larger scale factor, and then scale it down in Photoshop (Image > Image Size) using the Automatic resampling option (see below). By performing the scaling in Photoshop, you have more control over the resampling and scaling quality. This also reduces the burden on the raster image processor (RIP) that ultimately handles your job because it doesn’t have to process unnecessary pixels.
- Will the image be rotated in its final use? Shoot or scan the image at the correct angle. Photography may be more challenging (“Can you stand on your head just a little bit longer?”). As with scaling, you’ll achieve better results by performing the rotation in Photoshop rather than in a page-layout program. Because multiple rotations may slightly erode image detail, it’s best if you determine the correct final angle and perform a single rotation. If you anticipate doing a lot of experimentation with the angle of the image, consider using Smart Objects to minimize any data loss.
- What are the important elements in the image? If the image is a product shot, concentrate your efforts on maintaining the best detail and most faithful color rendition in the product, even if that means slightly hurting the incidental contents of the image. For example, worry about the red in the product package rather than agonizing over the color of the two partial tulips accenting the upper-right corner of the shot.
- Will the image be used on the Web as well as for print? Consider keeping the image in RGB as you perform color corrections and retouching work. Then save an RGB version of the image to be used as the source file for Web work. Save another copy of the image as CMYK for print. You should also keep your RGB working file in case you need to do additional work; this lets you regenerate the Web and print images from a new parent image if necessary.
- Will the image be printed on a digital press? Ask the printer if you need to convert to CMYK; it may be acceptable (or even preferable) to leave the image as RGB.
The rules for image resolution are the same as for image size because the concepts are intertwined. Start with as much image information as you can. You can always discard information, but you can’t convincingly create it out of nothing.
What’s the appropriate resolution? Generally speaking, 300 ppi at final size is sufficient for printing at 133–150 line screen. If your project will be printed at a very high line screen (175 lpi or above), and it is important to maintain a high level of detail in the content—images of jewelry, fine art, or antiques, for example—it may be beneficial to maintain a resolution greater than 300 ppi. Consult with the print service provider to determine the proper resolution for the job.
Photoshop CC Resampling Options
Resampling is the process of changing the amount of data in an image when the dimensions or resolution of an image are altered. When you scale down an image, pixels are discarded during the resampling process. When you scale up an image, new pixels are created to fill in the space between the original pixels. Choosing a resampling method allows you to determine how the process is performed. Photoshop offers seven options for the resampling method. Here’s how each method works.
- Preserve Details (enlargement): Uses Intelligent Upsampling and provides a Reduce Noise slider to prevent increased graininess in small detailed areas.
- Automatic: Photoshop examines the document and chooses an approach based on whether the image is being scaled up or down. Enlargements automatically use the Preserve Details option, but you’re not presented with the Reduce Noise slider.
- Bicubic Smoother (enlargement): Attempts to smooth out pixelation artifacts from enlargement.
- Bicubic Sharper (reduction): Interpolates color from surrounding pixels, then adds some unsharp masking to compensate for detail loss.
- Bicubic (smooth gradients): Produces smoother tonal gradations in smooth areas and gradients than Bilinear.
- Nearest Neighbor (hard edges): Appropriate for screen captures.
- Bilinear: Averages the color values of surrounding pixels.
TIP: Lab color uses a three-dimensional coordinate system, in which the L axis represents lightness, the a axis represents a linear path between red and green, and the b axis is a linear path between blue and yellow. Photoshop uses coordinates in Lab color space as reference points when converting images between RGB and CMYK.
Our eyes see a gamut of colors approximated by the coordinates in Lab color, we view work on our color monitors in RGB, and we print (usually) with CMYK. RGB is the native tongue for digital cameras and scanners. Even though an image may be fated to printing in CMYK, there are advantages to keeping the image in RGB as you perform color correction, retouching, and compositing. The wider color gamut of RGB is beneficial when you make color corrections, and many useful Photoshop tools, such as Vanishing Point, are not available for CMYK images.
Once you convert an image to CMYK for a given printing condition, you lose some flexibility. Keeping the image in RGB allows you to defer the conversion until later in the workflow rather than locking you in to a particular print condition early in the life of the job.
The color landscape is changing. Because of the increasing use of digital presses and large-format inkjet devices, RGB is no longer a forbidden color mode. In fact, it offers substantial benefits for digital output: The file size of a three-channel RGB image is only 75% of the size of the CMYK version of the image, and the larger color gamut of digital devices makes it possible to render more vibrant colors that would be lost in the conversion to CMYK.
Converting RGB to CMYK
If your printer instructs you to submit CMYK images, ask if they can provide conversion settings customized for their presses as well as instructions on applying those settings. Lacking that, you may find that Photoshop’s built-in conversion settings are serviceable. Choose Edit > Color Settings, and then select North America Prepress 2, or use the custom settings provided by your print service provider.
If you’d like to use an even better color setup, download and install the GRACoL (General Requirements for Applications in Commercial Offset Lithography) color settings files from the IDEAlliance Committee. The GRACoL committee produces guidelines and recommendations that are used as references throughout the printing industry.
A ZIP archive of the GRACoL color settings files can be downloaded from here.
Once you extract the files, install them according to your platform:
- Windows: Documents and Settings \ [Username] \ Application Data \ Adobe \ Color \ Settings
- Mac OS: Users / [Username] / Library / Application Support / Adobe / Color / Settings
To synchronize the color settings in all of the Creative Cloud applications simultaneously, launch Adobe Bridge and choose Edit > Color Settings. There are three color settings files within the download; choose the GRACoL setting that is appropriate for the kind of print work you are doing:
- GRACoL_Coated1_AdobeRGB: Commercial printing on high-quality Grade 1 or Grade 2 paper
- SWOP_Coated3_AdobeRGB: Publication printing on good-quality (Grade 3) paper
- SWOP_Coated5_AdobeRGB: Publication printing on lower-quality (Grade 5) paper
Photoshop applies these settings when you select Image > Mode > CMYK Color or Image > Mode > Grayscale, and also when you choose Edit > Convert to Profile. If you convert CMYK images to RGB to perform a color correction, or apply a filter that’s only available in RGB mode, your conversion back to CMYK will result in color values that differ from the original image supplied to you, although the change may not be apparent on your monitor. As long as your color settings are not extreme, this will probably not result in a drastic alteration of the printed piece, but it’s something you should consider before you begin repeatedly jumping between color spaces as you work on an image.
Working in Layers
While the intricacies of creating and editing Photoshop layers are beyond the scope of this chapter, it’s worth mentioning some of the benefits of working with layered files. Layers can keep the individual components of a complicated composition from being glued together prematurely, giving you a safety net in case you change your mind. Being able to use Photoshop’s History panel to backtrack is great during a working session, but it doesn’t help if you’ve saved a file and realize—days later—that you’ve inadvertently cropped out something crucial, or performed a color correction that doesn’t look so great.
Layers offer the advantage of using nondestructive methods for combining images, creating silhouette and soft-edged effects, and doing color corrections without permanently altering pixels.
Don’t Erase That Pixel!
If you need to eliminate part of an image, it’s tempting to just choose the Eraser tool from the Tools panel in Photoshop and get rid of it. When you permanently delete pixels, they’re gone forever. If you accidentally erased the CEO’s left ear in his portrait for the prestigious annual report, I hope you remember where you backed up the original image (see below). I’ll wait while you frantically search through that pile of CDs.
Nice seashore! Well, it was. Too bad you accidentally erased the ocean and some of the scenic rocks (right). But you still have the original image somewhere. Don’t you?
There’s a safer and more flexible way to eliminate pixels. Use the Layer Mask feature in Photoshop to selectively hide pixels without destroying them. If you can create a silhouette, you can create a layer mask.
- Create a selection by using your favorite method, and make sure it’s still an active selection. An active selection appears as a black-and-white dashed shape, often referred to as a selection marquee. Most users use the more colorful term “marching ants.”
- The layer must be a floating layer to use a layer mask. If the layer is named Background (and its name is italicized), it needs to first be converted to a floating layer. To do this, double-click the layer name. In the dialog box that is displayed, you can enter a new name for the layer or accept Photoshop’s default name for the newly floating layer.
- Make sure your ants are still marching, and then select Layer > Layer Mask > Reveal Selection, or just click the Add Layer Mask button on the bottom edge of the Layers panel. You should see the selected part of the image floating on a transparent background, and a mask icon will be added to the layer in the Layers panel (see below).
A layer mask hides and reveals content rather than erasing pixels. You can always modify the layer mask, to reveal or hide image contents in a nondestructive manner.
Color Corrections with a Safety Net
Some of the most commonly used color corrections can be stored in adjustment layers, which are nondestructive. No pixels are harmed in this type of color correction, and you can always change your mind later. The Adjustments panel in Photoshop CC provides quick access to the 15 adjustments that can be performed nondestructively.
You can choose from a wide assortment of color-correction options, including Curves, Levels, Color Balance, Brightness/Contrast, and more. When you select an adjustment, the Adjustments panel changes to display the options for that adjustment (see below). Controls on the bottom of the panel allow you to preview, reset, or cancel the adjustment.
In the Adjustments panel, select an adjustment to perform or select one of the adjustment presets from the list (left). The Properties panel opens to show you the options for the adjustment (right).
After performing an adjustment, you’ll see a new entry in the Layers panel. You can control the visibility and opacity of an adjustment layer as you would any layer.
An adjustment layer consists of two components—the adjustment and a mask. Initially, the mask is empty (that is, it isn’t hiding anything). But if you’d like to prevent the color correction from affecting some areas of the underlying image, use the Paintbrush tool to paint those areas of the mask with black. If you want to rework the color correction, double-click the icon in the adjustment layer to display the Properties panel, and change the options for the correction.
To disable the correction, click the eye icon to turn off the visibility of the adjustment layer. To permanently delete the adjustment layer, select the layer in the Layers panel, and then choose Delete Layer from the Layers panel menu, or drag the layer to the trash can at the bottom of the Layers panel (see below).
An adjustment layer performs a color correction without actually altering pixels. Don’t like it? Delete it or click the eye icon next to the layer to hide the correction.
If you scale an image, then rotate it, then scale it again, Photoshop performs three separate sets of interpolation. As a result, you lose a bit of data (and, therefore, detail) in each transformation. To minimize the data loss that results from transformations such as scaling or rotation, use Smart Objects when possible.
When you create a Smart Object, you’re embedding the original data of a raster or vector component in a Photoshop file. When you scale, distort, or rotate a Smart Object, Photoshop starts afresh with the stored data. This allows you to perform multiple transformations without multiple interpolations of data.
To embed a copy of a Photoshop, Illustrator, or PDF file, choose File > Place and select the file. Position and scale the artwork as necessary, and then press the Return or Enter key to finish the operation. A Smart Object is automatically created (see below). To convert an existing raster layer to a Smart Object, choose Convert to Smart Object from the Layers panel menu. If you copy and paste from an open Illustrator file, you have an option to paste as a Smart Object.
A special icon identifies a layer designated as a Smart Object.
There are important differences between a vector Smart Object and a pixel-based Smart Object. As you might expect, a vector Smart Object can be scaled up endlessly, whereas a pixel-based Smart Object can be scaled down without penalty, (but should not be scaled up much beyond its original size).
To edit a Smart Object, double-click it in the Layers panel. You can also select a Smart Object and choose Edit Contents from the Layers panel menu. Raster image content will be opened in Photoshop, and PDF or vector content will be opened in Illustrator. Perform any edits, and then save the edited file. The edited information is sent back to Photoshop, and the parent Photoshop file is automatically updated. Remember that an embedded Smart Object has no link to the original raster or vector art; what you’re editing is data that is embedded.
TIP: Adobe software provides multiple methods of accessing most commands, including menu choices, dialog boxes, panel menus, contextual menus, and keyboard shortcuts. Listing all of the options for every activity would double the size of this book. Although that would certainly result in a more impressive page count, it’s overkill. I encourage you to explore the options and find out which approach suits your style.
Sometimes Smart Objects Aren’t So Smart
Vector Smart Objects do have one limitation: While other vector content—such as shape layers, vector masks, or vector text—can be rendered as true vector art if the file is saved as a Photoshop PDF, Smart Objects will always render at the resolution of the containing image. If this presents a problem, consider performing a bit of surgery on the Photoshop file to separate the vector and raster components. Double-click vector content to open it in Illustrator, and then choose Save As to create a stand-alone Illustrator file. Delete or hide the vector Smart Object in the Photoshop image, and recombine the vector and raster components in Illustrator or InDesign.
A layer mask controls the visibility of the contents of a single layer, but a clipping mask controls the visibility of the contents of multiple layers. If you need to establish a common edge for multiple layers, this is a clever and flexible way to do so.
The Clipping Mask feature allows a layer to serve as a mask for layers above it, providing a common edge for all the layers.
Using a clipping mask requires a bit of upside-down thinking, though. We’re accustomed to a mask controlling what’s underneath it, based on real-world examples such as the mat around a framed watercolor. But a clipping mask falls below the content it masks. The color of the painted area of the mask layer isn’t important; it’s the transparency or opacity of each pixel in the mask layer that governs the transparency and opacity of the layers above it in the group.
To create a clipping mask group, make sure the bottom (mask) layer is a floating layer (i.e., not a glued-down Background layer). Select the layers immediately above the mask layer that you want to mask (but don’t select the mask layer), and choose Create Clipping Mask from the Layers panel menu. The indented appearance of upper layers and the downward-pointing arrows next to the layer icons indicate that the layers are being affected by the mask. To prevent one of the masked layers from being affected by the mask, select the affected layer (not the mask layer) and choose Release from Clipping Mask from the Layers panel menu.
Should You Flatten a Layered File?
Native Photoshop files offer the benefits of layers and transparency—what’s not to love? Because Illustrator and InDesign support unflattened native Photoshop files, there’s no need to flatten for compatibility if you’re using the image in those applications.
Admittedly, if a Photoshop file has grown to hundreds of megabytes, it might be more efficient to use a flattened file for placement into a page layout. In addition, you may have to flatten a file for a client who is using an application that only supports flattened formats, such as JPEG. But you’d be wise to keep a copy of the original layered Photoshop file in case you need to do additional edits. To flatten a layered file, choose Flatten Image from the Layers panel menu. You can also merge several layers; select the layers and choose Merge Layers from the Layers panel menu.
Adding effects such as ghosted areas or drop shadows is an easy way to add visual interest to images. Because you can incorporate Photoshop files into Illustrator drawings and Adobe InDesign pages, it’s important to realize that you’re governed by the limitations of those programs. Just because Photoshop can handle an effect doesn’t mean that other programs can interpret that content correctly.
For example, Illustrator and InDesign both honor opacity in placed Photoshop files, but neither program correctly handles Photoshop blending modes. Opacity settings and blending modes both fall under the heading of transparency, but they’re very different in how they’re rendered.
Opacity is expressed in terms of percentage. For example, a white square with 20% opacity allows what’s underneath to show through at 80% strength. Opacity settings in a Photoshop file are honored by InDesign and Illustrator, which enables you to create organic soft-edged mask effects and composite images together in InDesign or Illustrator files without having to combine the content in Photoshop.
However, blending modes involve much more complicated math. For example, drop shadows created in Photoshop by selecting Layer > Layer Style > Drop Shadow are set to use the Multiply blend mode with anything they encounter in Photoshop. This results in a realistic darkening of underlying image areas—but only within Photoshop.
Unfortunately, neither Illustrator or InDesign can understand blending modes within a Photoshop file. Consequently, drop shadows created in Photoshop do not interact correctly with underlying content when the native files are placed in Illustrator or InDesign (see below). Instead of darkening underlying elements, Photoshop shadows knock out the shadow area, eliminating content beneath.
When a Photoshop image containing a drop shadow is placed in another application, its shadow knocks out underlying color rather than darkening it (shown without the black plate).
What can you do to fix this? If an element requires a simple, soft-edged drop shadow like the effect shown below, the solution is simple: Don’t create the shadow in Photoshop. Instead, wait until the image is placed in Illustrator or InDesign and create the shadow there, as both applications handle their own shadows correctly.
However, if you want a cast shadow, such as that cast by a vase on a tabletop, you’ll have to perform a little trickery.
Silhouettes and Masking
Frequently, you will need to separate a subject from its background in order to composite the subject into another image or so the image can overlap other content in a layout. The proper choice of masking method depends on the subject and its intended use.
Creating a Path: Right and Wrong
If you need to isolate a subject with well-defined edges, such as a book or ball, the Pen tool in Photoshop provides precision and smoothness. Some people aren’t fond of the Pen tool, so they have instead become adept at avoiding the issue in several ways:
- Deciding that a square-cut image is much more tasteful
- Bribing someone else to draw the path
- Making a selection with the Magic Wand or Quick Selection tool and then converting the selection to a path
- The first two options are acceptable, but using the Magic Wand or Quick Selection tool will result in a lousy path. The Magic Wand is not truly magic (sorry). It’s acceptable for creating a selection to be used as a starting point for a mask, but it’s not the way to make a suitable path.
Photoshop attempts to convert an active selection (“marching ants”) to a clipping path, but the results are less than stellar. Because a selection follows the rectangular edges of pixels, it’s not a very good basis for a smooth clipping path; the sawtoothed edge of the selection will be faithfully rendered in the resulting path.
In some instances, noodling with the Make Work Path tolerance setting on the Paths panel (Window > Paths) can soften the granularity of the generated path, but you’ll have to keep reloading the selection and experimenting with the tolerance settings, because this function doesn’t offer any preview of the quality of the outcome.
The black line in the illustration below shows the unsavory result of taking the easy way out by converting a selection to a path, using the tightest tolerance setting, 0.5 pixels. Not only does the path created from a selection have a whopping 1,916 points, it’s unattractively irregular. The smooth gray line in the illustration was created, as you might suspect, with the Pen tool.
Comparing a Pen tool path (gray line) with a path created from a Magic Wand selection (black line).
Using a 10-pixel tolerance setting smooths out the path but results in a path that doesn’t fit the edge of the coin; it eliminates parts of the coin and includes slivers of the background. Face it: It’s far better to bite the bullet and draw the path with the Pen tool. There’s no need to obsessively follow every little imperfection. Because your goal is a reasonably faithful but smooth rendition of the object’s edge, it’s perfectly legal to take a bit of artistic license to improve the edge of the silhouetted image. For example, if you are creating a path to silhouette a gold ring that’s being held in place by a bit of wax, you draw along the smooth rim of the ring—you don’t include the lump of wax propping up the ring.
To use a path to knock out a subject when it’s placed in Illustrator or InDesign, select the path in the Paths panel, choose Save Path from the Paths panel menu, and give the path a name.
If you’re placing the image in Illustrator, you need to take one additional step: Return to the Paths panel menu and select Clipping Path. Choose your named path from the menu, and leave the Flatness field blank.
If you’re using the image in InDesign, there’s no need to designate the path as an official clipping path; just name and save the path. InDesign gives you the option to invoke the path for clipping if you want, or to ignore the path and display the unclipped image.
Path Flatness Settings
In the olden days of anemic RIPs, users were encouraged to set a high flatness value for paths to ease the burden on the RIP. Think of the RIP as constructing curved lines as a series of tiny straight segments. The fewer of those segments the RIP had to chisel—the flatter it could render curves—the faster the job would process. The illustration below shows a circle imaged with a high flatness setting. It might be easy on the RIP, but it’s not easy on the eye.
A high flatness setting makes things easier for the RIP, but it results in a harsh, chiseled appearance for what should be curved lines.
In reaction to seeing such clunky output, some people adopted the unfortunate habit of specifying very low flatness values in the Clipping Path dialog box, such as 0.2 device pixels, in the hopes that this would encourage the RIP to carve more petite segments. Forcing the RIP to chew this finely had the unpleasant side effect of slowing job processing and, in some cases, completely preventing the job from being processed by a RIP.
RIPs are more robust now, but the old habit of setting absurdly fine flatness settings persists. The truth is that it’s actually best to leave the Flatness field blank, which allows the RIP to use an optimal flatness setting without additional calculations. So stop agonizing over what to put in the Flatness field. Just leave it empty, and the RIP will do what it knows is best.
When specifying a clipping path, resist the urge to put a microscopic value in the Flatness field. Leaving it blank allows the imaging device to handle curves with an optimal setting
A dedicated tutorial on using the Pen tool is outside the scope of this book, but check the Appendix for some excellent references and tutorial resources.
Paths That Aren’t Clipping Paths
When placed in a page-layout application, an image with an official clipping path can only display what’s within the area of the clipping path—that’s the whole point of a clipping path.
Consider an image that contains several elements that you’d like to use selectively in a page layout. If you’re planning to use the clipping path approach to silhouetting those elements, you need to save multiple versions of the image, resulting in a separate image for each element you plan to use.
InDesign recognizes all paths in placed images, providing the option of choosing which path you’d like to use to silhouette the image. The paths just have to be named paths (an unsaved path, called a work path, will not be recognized). In InDesign, select the image, choose Object > Clipping Path > Options, and choose the name of the path to be used to silhouette the image.
InDesign allows you to specify which path to use for clipping. You can also ignore paths and just use the unclipped image.
Taking this approach allows you to use the same image in multiple ways without saving multiple versions. In the illustration below, the same image provides seven uses—a square-cut version and the six individual silhouetted pens. There is no limit to the number of named paths you can have in an image.
One image, multiple uses, thanks to optional paths in InDesign.
Silhouetting Soft-Edged Subjects
Here’s some good news for those who loathe the Pen tool—InDesign honors opacity in Photoshop images. In addition to providing liberation from the dreaded Pen tool, this also means that you can use layer masks to silhouette subjects with irregular, organic edges. Think of a mask as being much like a cardboard stencil. In a simple black-and-white mask, the black area is the equivalent of the cardboard; the white is equivalent to the hole cut out of the cardboard. But masks aren’t limited to just black and white: Gray areas in a mask result in translucency (i.e., areas that are not fully opaque)—perfect for subjects such as ice cubes or glass, which are not truly opaque.
Intelligent Edge Detection
Soft-edged components, such as fur or flyaway hair, simply aren’t candidates for the Pen tool (unless you’re a masochist with too much time on your hands). The Magic Wand and Quick Selection tool aren’t quite the answer, either; their selections can have harsh edges when they reach the end of a color area. But the Refine Edge feature can make all the difference.
Start with a Quick Selection or Magic Wand selection, then glance up in the Control panel: The Refine Edge option is available whenever you are using a selection tool and have an active selection. The Refine Edge functions let you preview and modify a potential mask, with sophisticated finessing features that really shine when you’re trying to capture organic edges. Using the Smart Radius option in the Refine Edge dialog box, you can capture delicate details that would be impossible with the Magic Wand or Quick Selection tools—and certainly not with the Pen tool.
The Edge Detection options in the Refine Edge dialog box make it possible to capture subtle organic edges.
Using the resulting selection as a layer mask is nondestructive—no innocent pixels are destroyed. The masked image can be placed in Illustrator and InDesign documents, maintaining the soft edges beautifully.
InDesign and Illustrator support soft-edged layer masks.
Creating Channel Masks
If a subject is photographed on a fairly consistent background (by which we don’t mean plaid), you can create a density-based mask similar to that of the dandelion shown here by starting with one of the channels of the image. Open the Channels panel in Photoshop (Window > Channels) to inspect the channels. Click the name of each channel, one by one, until you find the channel with the most contrast between the subject and the background. It doesn’t have to be perfect; you’re just looking for the best starting point for a mask. In the case of the dandelion, the cyan channel is the most promising. The black channel is a close second choice, but the cyan has finer detail, so it’s the winner.
Comparing channels to establish a good starting point for a mask. Either the cyan or black channel might work, but the cyan has more detail.
Once you’ve decided on the channel that provides the best start for a mask, select it and choose Duplicate Channel from the Channels panel menu. You can name it something memorable in the dialog box that follows, or just accept the default name—in this case, Cyan copy.
The next step is to manipulate the contrast in the Cyan copy channel so that it becomes solid black and white. Note that because you want to affect only the mask channel, rather than performing a color correction on the color image, you can’t use the Adjustments panel; adjustment layers can be applied to layers but not directly applied to channels.
Choose Levels (Image > Adjustments > Levels) or Curves (Image > Adjustments > Curves) to exaggerate the contrast in the mask channel. The goal with the dandelion image is to create a white dandelion-shaped hole in a black background. Because each image is different, you’ll have to experiment with the values in your images.
Using Levels to increase the contrast of the mask channel. There are no “best numbers”—correct values will vary for any given image.
You’ll almost always need to refine a mask with some manual touches. Paint with white to open up areas of the mask to reveal parts of the image. Paint with black to fill in the mask where you want to hide areas of the image. The mask is stored in an alpha channel. The alpha channel doesn’t act as a mask until you load it as an active selection. Since the mask is derived from image contents, it creates a much more natural silhouette without the hard-edged cutout appearance that results from using a clipping path.
When you create and save a mask, it’s stored in an alpha channel. But it’s just waiting there; it doesn’t serve as a mask until you load it as an active selection.
You’re not limited to just cyan, magenta, yellow, and black inks when you print a color image. You can create images that consist of combinations of CMYK and spot color, or even images that print only in spot colors.
A duotone image is composed of two colors, usually black and a spot color. Such images are a great way to add visual interest to a job with a limited color palette. There are variations on this theme, such as tritones (three colors), quadtones (four colors), and so on. Since these images contain spot-color components, it’s important to create them correctly to ensure that they print as intended. Multitone images may be composed of all spot colors or a combination of spot colors and process colors. To create duotones and their kin, start with a grayscale image, and then choose Image > Mode > Duotone. Initially, the Duotone Options dialog is set to Type: Monotone; just select Duotone from the pulldown menu.
When you choose the Duotone option, the Ink 1 position is populated by default with process black. Ink 2 is initially blank, unless you have previously created a duotone.
The Black ink listed for Ink 1 in the Duotone Options dialog box is not a spot color. It’s just the plain, old-fashioned process black of CMYK fame, and, unless the black component of the multitone image is intended to be a spot black, there’s no need to change it. Unless you’ve created a duotone previously, Ink 2 is unspecified.
To choose the second ink, click the white square next to Ink 2. In the Color Picker, click the Color Libraries button, and then choose the appropriate color book, such as PANTONE+ Solid Coated.
To assign a spot color to an ink, click Color Libraries and choose the color book in the Color Libraries dialog box.
Under the hood, a duotone (or any multitone image) is actually still the original grayscale image, with an embedded recipe governing the generation of the specified spot colors. You’ll notice that changing a grayscale to a duotone does not substantially increase the file size—that’s why.
Curves embedded in the duotone dictate the output on each plate.
Adding Spot Color to a CMYK Image
Special handling may be needed to accentuate portions of an image or to ensure faithful rendering of a color that falls outside the CMYK gamut. In this approach—variously called bump plate, touch plate, or kiss plate—spot colors are added to the image. Bump plates are often used in high-end projects, such as fine art reproductions or crucial product shots, to ensure a closer rendition of the original artwork.
To add a spot color to a CMYK image, choose New Spot Channel from the Channels panel menu. Click on the Color block to select an ink color, and then click on the Color Libraries button to access the standard color books. Choose the correct ink from the color list, and then click OK. In the New Spot Channel dialog box, don’t modify the name. The Solidity option controls visual opacity of the spot ink plate as it is displayed in Photoshop; it has nothing to do with how the plate will print. Varying the Solidity setting may make it easier for you to work on the spot channel, but the actual contents of the channel will not be affected by the Solidity setting.
Click the Color block to pick a color. The Solidity block controls the onscreen appearance, not how the ink prints.
There’s a bit of finesse involved in creating a bump plate, since it’s usually intended to supplement or replace parts of the process components. The preview on your color monitor may suggest the results, but you’ll need to see color proofs from the printer to truly judge the outcome.
In the rose image, the PANTONE+ 805 fluorescent pink plate was derived from the magenta plate; the magenta plate was lightened somewhat to “leave room” for the fluorescent spot color plate.
The PANTONE 805 bump plate intensifies the pink color of the rose beyond what’s possible with just the CMYK process inks.
Save the image as Photoshop PSD; it will print correctly when placed in InDesign or Illustrator. You may have to turn on Overprint Preview in those applications to make the bump plate visible, but you can easily check by choosing Window > Separations Preview in Illustrator or Window > Output > Separations Preview in InDesign. If the file contains vector content such as type or shape layers that should image as vector, you should save the file as a Photoshop PDF.
Creating a Spot Varnish Plate
Even though it isn’t usually colored, a spot varnish plate is handled just like a spot color ink. A spot varnish is a shaped application of varnish, commonly used to highlight an object, as opposed to an all-over flood varnish.
To create a spot varnish plate, start as you would when creating a spot color: Choose New Spot Channel from the Channels panel menu. Name the varnish plate to be consistent with any existing art files (or ink already created in Illustrator or InDesign). Click the Color block in the Spot Channel dialog box and create a color mix in keeping with existing files. If you’re starting fresh, consider naming the channel Spot Varnish and coloring it something obvious, such as an obnoxious bright green, so it will be easy to identify when placed into other applications.
Create the varnish area in the spot channel by painting or pasting content: Solid areas in the varnish channel represent the areas where the solid varnish will be printed.
The spot varnish plate (right) will result in a gloss varnish printed to highlight parts of the antique motorcycle. When you place an image with a spot color or spot varnish plate into an Illustrator or InDesign document, the spot color is automatically added to the Swatches list.
Pixels and vectors can live together in graphic harmony, enabling you to combine smooth, sharp text with images for interesting results. While Photoshop is primarily devoted to pixels, it is possible to add text and other vector elements to a Photoshop image. It’s not appropriate to create body text in Photoshop, and most text should be typeset in an illustration or page-layout application. But if you want to bevel and emboss text, or give a special treatment to a vector logo, you may be compelled to handle it in Photoshop.
Vector and text elements can be an interesting addition to an image.
Vector elements in Photoshop do not have any inherent resolution, although any shading applied through effects such as embossing must be accomplished with pixels. Those pixels are just part of the effect, and they don’t become literal pixels until the file is printed. Consequently, you can scale vector elements within the Photoshop image and the effects will be recalculated, growing new pixels of the appropriate resolution. Because the vector elements are truly vector, not pixels, they remain editable.
Unfortunately, when PSD files containing text or vector content are placed in an illustration or page-layout file, the vector edges are rendered as pixels during output, taking on the resolution of the underlying image.
The solution to this dilemma is to save the image as a Photoshop PDF. A Photoshop PDF can be reopened by Photoshop without rasterizing, and the vector content is imaged as vector when the file is placed into Illustrator and InDesign. Think of it as two files in one: Photoshop sees the original PSD, with its editable text and vector content, and other applications see the public face of the PDF file, with its nice, crisp edges. Fonts are embedded, so any text will print correctly.
Text or vector components render as pixels in a PSD file (left) but correctly render as vector in a Photoshop PDF (right).
Saving As a Photoshop PDF
To save a PDF that can be reopened by Photoshop, choose File > Save As, and then in the Format menu, select Photoshop PDF. When the Save Adobe PDF dialog is displayed, make sure the Preserve Photoshop Editing Capabilities box is checked.
To maintain transparency in the image when it is placed into Illustrator or InDesign, you must save with Acrobat 5.0 or above compatibility. If you open the file from within Photoshop, everything is still editable; layers and text are intact. If you double-click the file, it will launch Acrobat Pro or Adobe Reader, depending on your system’s file associations.
Saving for Other Applications
The old recommendations to save as TIFF or EPS were solid in their day, however, today native layered Photoshop files offer appealing features such as transparency, editable vector elements, and nondestructive color corrections. InDesign allows you to control the visibility of placed, layered, native Photoshop files (but not TIFFs). TIFF files can contain layers but offer no support for vector elements, so Photoshop PSDs and PDFs trump TIFF files for flexibility.
It’s now acceptable to loosen up a bit. InDesign and Illustrator accept layered Photoshop files in all their glory, including transparency effects. There’s no need to squeeze the fun out of your images before you place them into a page-layout document. But it’s still worthwhile to do some housecleaning before you save and close your Photoshop file.
- Delete unused layers. Select an unwanted layer (or Shift-click to select multiple layers), and then choose Delete Layer from the Layers panel menu.
- Delete unused alpha channels. Select an unwanted channel (or Shift-click to select multiple channels), and then choose Delete Channel from the Channels panel menu.
- Delete unused paths. Select the unwanted path, and then choose Delete Path from the Paths panel menu. You’ll have to delete paths one by one, as Shift-clicking doesn’t allow you to select multiple paths in the panel.
- Make sure the image is in the correct color space for its final use.
- If you’re certain about the final use of the image, crop out any unnecessary image content. But leave a rind of extra image around the outside, just in case you need a bit of elbow room when the image is placed in a page layout.
- If you’ve created multiple, experimental files on your way to the final image, name the final image in a way that makes it clear It’s The One, and put the older, obsolete files in a quarantine folder. Don’t send a job to the print service provider with a folder full of images with names like Final.psd, Final2.psd, NewFinal.psd, Newfinal2.psd, NewerFinal3.psd, NewestFinal.psd, OldFinalDon’tUse.psd, and so on. If you’re confused, think how they’ll feel. Many graphic artists append an identifying suffix such as r1 for Revision 1, or v2 for Version 2. So the 23rd version of a cover image might be called CoverPhoto_v23.psd. Feel free to use a sensible naming convention that works for you.
Excerpted from Real World Print Production with Adobe Creative Cloud by Claudia McCue. Copyright © 2014 Used with permission of Pearson Education, Inc. and Peachpit Press.