Photoshop.CS.Bible [Electronic resources] نسخه متنی

File Format Roundup

Photoshop CS supports more than 25 file formats from inside its Open and Save dialog boxes. It can support even more through the addition of plug-in modules, which attach commands to the File Save As, File Import, and File Export submenus.

File formats represent different ways to save a file to disk. Some formats provide unique image-compression schemes, which save an image in a manner that consumes less space on disk. Other formats enable Photoshop to trade images with different applications running under Windows, the Mac, or some other platform.

The native format

Like most programs, Photoshop offers its own native format — that is, a format optimized for Photoshop's particular capabilities and functions. This .psd format saves every attribute that you can apply in Photoshop — including layers, extra channels, file info, and so on — and is compatible with Versions 3 and later of the program. Of course, when you open files in earlier versions of Photoshop, you lose file attributes related to later versions, such as annotations, color proof options, and so on.

The downside of the Photoshop format is that relatively few applications other than Photoshop support it, and those that do don't always do a great job. Some applications, such as Corel Photo-Paint and Adobe After Effects, can open a layered Photoshop image and interpret each layer independently. But most of the others limit their support to flat Photoshop files. To accommodate these programs, you can either deselect the Layers check box in the Save dialog box to save a flattened version of the image or set the Maximize PSD File Compatibility option in the Preferences dialog box to Ask or Always.

However, I intensely dislike both of these options. (In fact, you should be sure to set Maximize PSD File Compatibility to Never, for reasons explained in Chapter 2.) The native .psd format was never intended to function as an interapplication standard; it was meant for Photoshop alone. So use it that way. If you want to trade a flattened image with some other program, use TIFF, JPEG, or one of the other universal formats explained in this chapter.

Special-purpose formats

With so many file formats to choose from, you can imagine that most are not the kinds you'll be using on a regular basis. In fact, apart from the native Photoshop format, you'll probably want to stick with TIFF, JPEG, and GIF for Web images and EPS when preparing images for placement in InDesign, QuarkXPress, and other layout programs.

Many of the other formats are provided simply so that you can open an image created on another platform, saved from some antiquated paint program, or downloaded from the Web. In the spirit of sweeping away the chaff so we can move on to the good stuff, I cover these special-purpose formats first.

Microsoft Paint's BMP

BMP (Windows Bitmap) is the native format for Microsoft Paint (included with Windows) and is supported by a variety of Windows and DOS applications. Photoshop supports BMP images with up to 16 million colors. You also can use RLE (Run-Length Encoding), a lossless compression scheme specifically applicable to the BMP format.

The most common use for BMP is to create images for use in help files and Windows wallpaper. In fact, rolling your own wallpaper is a fun way to show off your Photoshop skills. For the best results, make sure you set your image to exactly the same pixel dimensions as your screen (which you can check from the Settings panel in the Display control panel). To conserve memory, you may want to reduce the number of colors in your wallpaper image to 256 using Image Mode Indexed Color.

When you save the wallpaper image, Photoshop displays the options shown in Figure 3-15. Generally, you'll want to select the Windows and Compress (RLE) options, but it really doesn't matter when creating wallpaper. Don't mess with the Depth options. Either you reduced the bit depth using the Indexed Color command as I directed previously or you didn't. There's no sense in changing the colors during the save process.

Figure 3-15: Select the options shown here when saving a BMP image for use as a desktop background. Leave the Depth setting alone.

To load the wallpaper onto your PC desktop, right-click anywhere on the desktop and choose the Properties command. This brings up the Display Properties dialog box. Click the Browse button and locate your BMP image on disk. Then click the Apply button to see how the image looks.

Camera Raw

Cineon

CompuServe's GIF

In the old days, the CompuServe online service championed GIF (short for Graphics Interchange Format) as a means of compressing files so you could quickly transfer photographs over your modem. Like TIFF, GIF uses LZW compression, but unlike TIFF, GIF is limited to just 256 colors.

Over the years the GIF format has grown slightly more sophisticated. You can save an image with or without transparency by choosing File Save and then choosing CompuServe GIF from the Format pop-up menu. When you index (reduce) the image to 256 colors — which you can do either before or during the file save process — select the Transparency check box in the Indexed Color dialog box if you want any transparent areas of the image to remain transparent when you view the image file in a Web browser.

PC Paintbrush's PCX

PCX doesn't stand for anything. Rather, it's the extension PC Paintbrush assigns to images saved in its native file format. Although the format is losing favor, many PCX images are still in use today, largely because PC Paintbrush is the oldest painting program for DOS. Photoshop supports PCX images with up to 16 million colors. You can find an enormous amount of art, usually clip art, in this format. However, don't save files to PCX unless a client specifically demands it. Other formats are better.

Adobe's paperless PDF

PDF (Portable Document Format) is a variation on the PostScript printing language that enables you to view electronically produced documents on screen. This means you can create a publication in QuarkXPress or InDesign, export it to PDF, and distribute it without worrying about color separations, binding, and other printing costs. Using a program called Adobe Acrobat, you can open PDF documents, zoom in and out of them, and follow hypertext links by clicking highlighted words. Adobe distributes Mac, Windows, and UNIX versions of the Adobe Reader for free, so almost anyone with a computer can view your stuff in full, natural color.

You open PDF files in different ways depending on what elements of the file you want to access:

Use File Open to open a particular page in a multipage PDF file. After selecting the page you want to view, you can set the image size and resolution of the rasterized file. You also can choose File Place to add a page as a new layer to an open image; in this case, you can't control the size and resolution before adding the page. However, you can scale the page after the fact as you can any layer.

Choose File Import PDF Image to bring up a dialog box that enables you to open a particular image in the PDF file.

Choose File Automate Multi-Page PDF to PSD to turn each page in the PDF file into a separate Photoshop image file.

The real question, however, is why would you want to open or place a PDF file in Photoshop instead of viewing it in Acrobat, which provides you with a full range of document-viewing tools not found in Photoshop? Furthermore, because you can save only single-page PDF files, why on earth would you save to PDF in Photoshop?

I can think of two scenarios where Photoshop's PDF functions may come in handy:

You want to see how images in a PDF document will look when printed on a high-resolution printer. Open the PDF file using File Open, set the resolution to match that of the output device, and eyeball those images on screen. This "soft-proofing" technique enables you to spot defects that may not be noticeable in draft proofs that you output on a low-res printer.

You need a convenient way to distribute images for approval or input. You can save an image as a PDF file and send it to clients and colleagues, who can view the image in Acrobat or the Adobe Reader if they don't have Photoshop. You can even add text or voice annotations to your PDF file. In addition to annotations, Photoshop PDF supports layers, transparency, embedded color profiles, spot colors, duotones, and more. This enables you to route an image for approval without having to flatten the image or otherwise strip it of its Photoshop features. Of course, features not supported by Acrobat aren't accessible to the viewer.

When you save to PDF in Photoshop, you have a choice of two encoding options, as shown in Figure 3-16. Choose ZIP only for images that feature large expanses of a single color; otherwise, opt for JPEG. Keep the Quality option set to Maximum to maintain the best print quality, just as you do for regular JPEG files.

Figure 3-16: Photoshop offers some great features in the PDF Options dialog box.

When saving to PDF, you also encounter several other options:

Save Transparency: If your image has transparency and you're saving it as a PDF without layers, the Save Transparency check box determines whether or not the transparency will be maintained.

Image Interpolation: Selecting this option enables other programs to interpolate the image when resampling to another size.

Downgrade Color Profile: Here's an option you'll probably never use. PDF doesn't support Version 4 ICC profiles. Selecting this check box converts them to Version 2 profiles so that they'll work in PDF. The thing is, you probably don't have a Version 4 ICC profile anyway, in which case this option is dimmed. For more on ICC profiles, see Chapter 16.

PDF Security: This option allows you to assign passwords to PDF documents — if users don't know the password, they can't open the document. To set the security information, select the PDF Security check box and click the Security Settings button. You can set the user password here, along with a master password, which can prevent others from changing the user password. The Encryption Level options take effect only when the document is being opened with Adobe Acrobat; you can choose the version of Acrobat and determine whether options such as saving changes and printing are allowed.

Include Vector Data and Embed Fonts: Select these two check boxes to retain any vector graphics and font data, respectively. Alternatively, you can select Use Outlines for Text to save text as character outlines that are editable in the PDF file.

Apple's PICT

PICT (Macintosh Picture) was the native graphics format for Mac OS 9. (Mac OS X has adopted PDF as its standard graphics file format.) Based on the QuickDraw display language that the system software uses to convey images on screen, PICT handles object-oriented artwork and bitmapped images with equal aplomb. It supports images in any bit depth, size, or resolution. PICT even supports 32-bit images, so you can save a fourth masking channel when working in the RGB mode.

If you've installed QuickTime on the Mac, you can subject PICT images to JPEG compression. But although PICT's compression options may look similar to JPEG's, they are actually significantly inferior. The differences become especially noticeable if you open an image, make a change, and again save it to disk, effectively reapplying the compression.

In most cases, you'll want to use the JPEG format instead of PICT when compressing images. JPEG images are compatible with the Web; PICT images are not. Also, more Windows applications recognize JPEG than PICT, and it's extremely difficult to find a Windows program that can handle PICT files with QuickTime compression.

In fact, the only reason to use PICT is low-end compatibility. If you're trying to save an image in a format that your mom can open on her Mac, for example, PICT may be a better choice than JPEG. Heck, you can open PICT files inside a word processor, including everything from SimpleText to Microsoft Word. Just be sure mom has QuickTime loaded on her machine.

When you save a PICT image, Photoshop also lets you set the bit depth. You should always stick with the default option, which is the highest setting available for the particular image. Don't mess around with these options; they apply automatic pattern dithering, which is a bad thing.

If you're using a PC, you may need to open a PICT file a Mac friend sends you. Photoshop can do this, but one thing may trip you up: On the Mac, you have the option of saving PICT files with a variety of JPEG compressions supplied by Apple's QuickTime. Unless you have QuickTime installed on your PC — which you might if you do a lot of surfing on the Web — you won't be able to open compressed PICT images.

PICT resource

PICT resources were the images contained in the resource fork of a Mac file in OS 9. (Windows programs can't recognize resource forks, so this section is only relevant to Mac folks.) The only reason you would want to save a PICT resource is if you are creating an OS 9 startup screen, and the most likely reason to open one is to extract images from the OS 9 Scrapbook. However, since Photoshop CS no longer runs under OS 9, you can be fairly confident that you won't be using this format. For the time being, however, Photoshop continues to support the format.

Pixar workstations

Pixar has created some of the most memorable computer-animated short films and features in recent memory. From the desk lamps playing with a beach ball in Luxo, Jr. to the artistic triumphs that were Toy Story, Monsters, Inc., and Finding Nemo, Pixar continues to blaze a trail in this spectacular new art form.

Pixar works its 3-D magic using mondo-expensive proprietary workstations. Photoshop enables you to open a still image created on a Pixar machine or to save an image to the Pixar format so you can integrate it into a 3-D rendering. The Pixar format supports grayscale and RGB images.

PNG for the Web

Pronounced ping, the PNG format enables you to save 16 million color images without compression for use on the Web. Although PNG has been generally supported by Netscape Navigator and Microsoft Internet Explorer since 1997, these main two browsers still can't be counted on to fully support all the features of PNG. Couple that info with the obvious fact that you can't count on the general public to have anywhere near the most recent version of any software application, and using PNG begins to seem like a dicey proposition. It's a great format, though, offering full-color images without the pesky visual compression artifacts you get with JPEG. I believe that PNG will one day be a big player.

Large Document Format (PSB)

Photoshop CS is capable of opening and saving existing PSB files by default, but if you want to create a Large Document Format file from scratch, you need to turn on the Enable Large Document Format (.psb) option in the File Handling panel of the Preferences dialog box (that's Ctrl+K, Ctrl+2 on the PC and z -K, z -2 on the Mac). Keep in mind that images saved in PSB format cannot be opened in other applications or previous versions of Photoshop.

Scitex image-processors

Some high-end commercial printers use Scitex printing devices to generate color separations of images and other documents. Photoshop can open images digitized with Scitex scanners and save the edited images to the Scitex CT (Continuous Tone) format. Because you need special hardware to transfer images from the PC to a Scitex drive, you'll probably want to consult with your local Scitex service bureau technician before saving to the CT format. The technician may prefer that you submit images in the native Photoshop, TIFF, or JPEG format. The Scitex CT format supports grayscale, RGB, and CMYK images.

TrueVision's TGA

TrueVision's Targa and NuVista video boards enable you to overlay computer graphics and animation onto live video. The effect is called chroma keying because, typically, a key color is set aside to let the live video show through. TrueVision designed the TGA (Targa) format to support 32-bit images that include 8-bit alpha channels capable of displaying the live video. Support for TGA is widely implemented among professional-level color and video applications on the PC.

Acrobat TouchUp Image

If your preferences are set correctly in Adobe Acrobat, you can select any image file in a PDF document, right-click it (Control-click on the Mac), and choose to edit the image externally in Photoshop. Acrobat creates a temporary file with a long, indecipherable name, called a TouchUp Image, and opens Photoshop. After you save the file and return to Acrobat, the changes you made are incorporated automatically. A quick tip: Make sure you don't alter the dimensions of an image you're touching up — doing so will alter the layout of the PDF file — and remember to flatten any layers you may have created before you return to Acrobat.

Wireless Bitmap

Hey, those crude little graphics found on handheld wireless devices have to come from somewhere, right? Why not Photoshop? Photoshop can open and save in WBMP (Wireless Bitmap) format, an up-and-coming standard for cell phones and personal digital assistants. To save an image to the Wireless Bitmap format, the image must be in Bitmap mode, with only black and white pixels.

Interapplication formats

In the name of interapplication harmony, Photoshop supports a few software-specific formats that permit you to trade files with popular object-oriented programs, such as Illustrator and QuarkXPress. Every one of these formats is a variation on EPS (Encapsulated PostScript), which is based in turn on Adobe's industry-standard PostScript printing language.

Rasterizing an Illustrator or FreeHand file

Photoshop supports object-oriented files saved in the EPS format. EPS is specifically designed to save object-oriented graphics that you intend to print to a PostScript output device. Just about every drawing and page-layout program on the planet (and a few on Mars) can save EPS documents.

Prior to Version 4, Photoshop could interpret only a small subset of EPS operations supported by Illustrator (including the native .ai format). But then Photoshop 4 came along and offered a full-blown EPS translation engine, capable of interpreting EPS illustrations created in FreeHand, CorelDraw, Deneba's Canvas, and more. You can even open EPS drawings that contain imported images, something else Version 3 could not do.

When you open an EPS or native Illustrator document, Photoshop rasterizes (or renders) the artwork — that is, it converts the artwork from a collection of objects to a bitmapped image. During the open operation, Photoshop presents the Rasterize Generic EPS Format dialog box (see Figure 3-17), which enables you to specify the size and resolution of the image, just as you can in the New dialog box. Assuming the illustration contains no imported images, you can render it as large or as small as you want without any loss of image quality.

Figure 3-17: You can specify the size and resolution at which Photoshop renders an EPS illustration.

You should always select the Anti-aliased check box unless you're rendering a very large image — say, 300 ppi or higher. Antialiasing blurs pixels to soften the edges of the objects so they don't appear jagged. When you're rendering a very large image, the difference between image and printer resolution is less noticeable, so antialiasing is unwarranted.

Photoshop renders the illustration to a single layer against a transparent background. Before you can save the rasterized image to a format other than native Photoshop, you must eliminate the transparency by choosing Layer Flatten Image. Or save a flattened version of the image to a separate file by choosing the As a Copy option in the Save dialog box.

If Photoshop can't parse the EPS file — a techy way of saying Photoshop can't break down the individual objects — it attempts to open the PICT (Mac) or TIFF (Windows) preview. This exercise is usually futile, but occasionally you may want to take a quick look at an illustration to, say, match the placement of elements in an image to those in the drawing.

Placing an EPS illustration

If you want to introduce an EPS graphic into the foreground image rather than render it into a new image window of its own, choose File Place. Unlike other File menu commands, Place supports only EPS illustrations and PDF files.

After you import the EPS graphic, it appears inside a box — which Photoshop calls a bounding box — with a great big X across it. You can move, scale, and rotate the illustration into position before rasterizing it to pixels. Drag a corner handle to resize the image; drag outside the image to rotate it. You can also nudge the graphic into position by pressing the arrow keys. When everything is the way you want it, press Enter (or Return on the Mac) or double-click inside the box to rasterize the illustration. If the placement isn't perfect, not to worry. The graphic appears on a separate layer, so you can move it with complete freedom. To cancel the Place operation, press Escape instead of Enter or Return.

Saving an EPS image

Chapter 8, a clipping path defines a free-form boundary around an image. When you place the image into an object-oriented program, everything outside the clipping path becomes transparent. While some programs — notably InDesign and PageMaker — recognize clipping paths saved with a TIFF image, many programs acknowledge a clipping path only when saved in the EPS format.

Third, although Illustrator has remedied the problems it had importing TIFF images, it still likes EPS best, especially where screen display is concerned. Thanks to the EPS file's fixed preview, Illustrator can display an EPS image on screen very quickly compared with other file formats. And Illustrator can display an EPS image both in the preview mode and in the super-fast artwork mode.

So if you want to import an image into Illustrator, QuarkXPress, or another object-oriented program, your best bet is EPS. On the downside, EPS is an inefficient format for saving images thanks to the laborious way that it describes pixels. An EPS image may be three to four times larger than the same image saved to the TIFF format with LZW compression. But this is the price we pay for reliable printing.

To save an image in the EPS format, choose Photoshop EPS from the Format pop-up menu in the Save dialog box. After you press Enter or Return, Photoshop displays the dialog box shown in Figure 3-18. The options in this dialog box work as follows:

Figure 3-18: When you save an image in the EPS format, you can specify the type of preview and tack on some printing attributes.

Preview: Technically, an EPS document comprises two parts: a pure PostScript-language description of the graphic for the printer and a bitmapped preview so you can see the graphic on screen. On a PC, select the TIFF (8 bits/pixel) option from the Preview pop-up menu to save a 256-color TIFF preview of the image. On a Mac, select the Macintosh (8 bits/pixel) option from the Preview pop-up menu to save a 256-color PICT preview of the image. Or select the Macintosh (JPEG) option for a 24-bit preview (which in most cases takes up less room on disk, thanks to the JPEG compression). If you plan on passing off the image to a Windows colleague, select TIFF (8 bits/pixel). The 1-bit option provides a black-and-white preview only, which is useful if you want to save a little room on disk. Select None to include no preview and save even more disk space.

Encoding: If you're saving an image for import into Illustrator, QuarkXPress, or some other established program, select the Binary encoding option (also known as Huffman encoding), which compresses an EPS document by substituting shorter codes for frequently used characters. The letter a, for example, receives the 3-bit code 010, rather than its standard 8-bit ASCII code, 01100001 (the binary equivalent of what we humans call 97).

Sadly, some programs and printers don't recognize Huffman encoding, in which case you must select one of the less efficient ASCII options. ASCII stands for American Standard Code for Information Interchange, which is fancy jargon for text-only. In other words, you can open and edit an ASCII EPS document in a word processor, provided you know how to read and write PostScript.

So to recap, ASCII results in really big files that work with virtually any printer or application. Binary creates smaller files that work with most mainstream applications but may choke some older-model printers. And the JPEG settings are compatible exclusively with Level 2 and later PostScript printers.

Include Halftone Screen: Another advantage of EPS over other formats is that it can retain printing attributes. If you specified a custom halftone screen using the Screens button in the Page Setup dialog box, you can save this setting with the EPS document by selecting the Include Halftone Screen check box. But be careful — you can just as easily ruin your image as help it. Read Chapter 18 before you select this check box.

Include Transfer Function: As described in Chapter 18, you can change the brightness and contrast of a printed image using the Transfer button in the Page Setup dialog box. To save these settings with the EPS document, select the Include Transfer Function check box. Again, this option can be dangerous when used casually. See Chapter 18 for more details.

PostScript Color Management: Like JPEG compression, this check box is compatible with Level 2 and 3 printers only. It embeds a color profile, which helps the printer to massage the image during the printing cycle to generate more accurate colors. Unless you plan on printing to a Level 2 or later device, leave the option off. (For more information about color profiles, read Chapter 16.)

Include Vector Data: Select this option if your file contains vector objects, including shapes, nonbitmap text, and layer clipping paths. Otherwise, Photoshop rasterizes the objects during the save process. When you select the option, Photoshop displays a warning in the dialog box to remind you that if you reopen the file in Photoshop, you rasterize any vector objects that you saved with the file.

Transparent Whites: When saving bitmap mode images as EPS files in Photoshop, the four check boxes previously discussed drop away, replaced by Transparent Whites. Select this option to make all white pixels in the image transparent.

Although Photoshop EPS is the only format that offers the Transparent Whites option, many programs — including Illustrator and InDesign — treat white pixels in black-and-white TIFF images as transparent as well.

Image Interpolation: General preferences" section in Chapter 2.) Unless you have a reason for doing otherwise, turn this option on.

QuarkXPress DCS

Quark developed a variation on the EPS format called DCS (Desktop Color Separation). When you work in QuarkXPress, PageMaker, and other programs that support the format, DCS facilitates the printing of color separations. Before you can use DCS, you have to convert your image to the CMYK color space using Image Mode CMYK Color. (DCS 2.0 also supports grayscale images with spot-color channels.) Then bring up the Save dialog box and select Photoshop DCS 1.0 or 2.0 from the Format pop-up menu.

Photoshop 5 introduced support for DCS 2.0 to accommodate images that contain extra spot-color channels, as explained in Chapter 18. If you add a Pantone channel to an image, DCS 2.0 is the only PostScript format you can use. If your image doesn't contain any extra channels beyond the basic four required for CMYK, DCS 1.0 is the safer and simpler option.

After you press Enter or Return, Photoshop displays an additional pop-up menu of DCS options, which vary depending on whether you've selected DCS 1.0 or 2.0, as shown in Figure 3-19. The DCS 1.0 format invariably saves a total of five files: one master document (which is the file that you import into QuarkXPress) plus one file each for the cyan, magenta, yellow, and black color channels (which are the files that get printed). The DCS 2.0 format can be expressed as a single file (tidier) or five separate files (better compatibility).

Figure 3-19: The extra options for the DCS 1.0 format (top) and those for the DCS 2.0 format (bottom).

Either way, the DCS pop-up menu gives you the option of saving a 72-ppi PostScript composite of the image inside the master document. Independent from the bitmapped preview — which you specify as usual by selecting a Preview option — the PostScript composite makes it possible to print a low-resolution version of a DCS image to a consumer-quality printer. If you're using a black-and-white printer, select the 72 pixel/inch grayscale option; if you're using a color printer, select the final option. Be forewarned, however, that the composite image significantly increases the size of the master document on disk. The two options at the bottom of the options dialog boxes for DCS 1.0 and 2.0, Include Vector Data and Image Interpolation, work just as described earlier for the Photoshop EPS format.

Premiere Filmstrip

Adobe Premiere Pro is a popular video-editing application for the PC. The program is a wonder when it comes to fades, frame merges, and special effects, but it offers no frame-by-frame rotoscope-style animating capabilities. For example, you can neither draw a mustache on a person in the movie nor can you make brightly colored brushstrokes swirl about in the background — at least, not in Premiere.

You can export the movie to the Filmstrip format, though, which is a file-swapping option exclusive to Photoshop and Premiere. A Filmstrip document organizes frames in a long vertical strip, as shown on the left side of Figure 3-20. The right side of the figure shows the movie after I edited each individual frame in ways not permitted by Premiere. A boring movie of a cat stuck in a bag becomes an exciting movie of a flying cat-stuck-in-a-bag. If that doesn't sum up the miracle of digital imaging, I don't know what does.

Figure 3-20: Four frames from a QuickTime movie as they appear in the Filmstrip format before (left) and after (right) editing the frames in Photoshop.

A gray bar separates each frame. The number of each frame appears on the right; the SMPTE (Society of Motion Picture and Television Engineers) time code appears on the left. The structure of the three-number time code is minutes:seconds:frames, with 30 frames per second.

And finally — here's the great one — you can select several sequential frames and edit them simultaneously by following the next set of steps.

STEPS: Selecting Sequential Frames in a Movie

Select the first frame you want to edit. Select the rectangular marquee tool by pressing the M key. Then drag around the area you want to edit in the movie. (This is the only step that takes any degree of care or coordination whatsoever.)

Switch to the quick mask mode by pressing the Q key. The areas around the selected frame are overlaid with pink.

Set the magic wand Tolerance value to 0. Select the magic wand tool. Then, in the Options bar, enter 0 for the Tolerance value and deselect the Anti-aliased check box.

Click inside the selected frame (the one that's not pink) with the magic wand tool. This selects the unmasked area inside the frame.

Press Ctrl+Shift+Alt+down arrow (z -Shift-Option-down arrow on the Mac) to clone the unmasked area to the next frame in the movie. When you exit the quick mask mode, both this frame and the one above it will be selected.

Repeat several times. Keep Ctrl+Shift+Alt+down arrowing until you're rid of the pink stuff on all the frames you want to select.

Exit the quick mask mode by pressing the Q key again. All frames appear selected.

Edit the frames to your heart's content.

The process of editing individual frames as just described is sometimes called rotoscoping, named after the traditional technique of using live-action film as a source when creating animated sequences. You also can try out some scratch-and-doodle techniques, which is where an artist scratches and draws directly on frames of film. If this isn't enough, you can emulate xerography, in which an animator makes Xerox copies of photographs, enhances the copies using markers or whatever else is convenient, and shoots the finished artwork, frame by frame, on film. In a nutshell, Photoshop extends Premiere's functionality by adding animation to its standard supply of video-editing capabilities.

You can save an image in the Filmstrip format through the Save dialog box. But remember, you can save in this format only if you opened the image as a Filmstrip document and did not change the size of the image.

The mainstream formats

The formats discussed so far are mighty interesting and they all fulfill their own niche purposes. But two formats — JPEG and TIFF — are the all-stars of digital imagery. You'll use these formats the most because of their outstanding compression capabilities and almost universal support among graphics applications.

JPEG

The JPEG format is named after the folks who designed it, the Joint Photographic Experts Group. JPEG is the most efficient and essential compression format currently available and is likely to be the compression standard for years to come. JPEG is a lossy compression scheme, which means it sacrifices image quality to conserve space on disk. You can control how much data is lost during the save operation, however.

When you save an image in the JPEG format, you're greeted with the JPEG Options dialog box (see Figure 3-21). The most vital option in this dialog box is the Quality setting, which determines how much compression Photoshop applies to your image.

Figure 3-21: The JPEG Options dialog box provides a total of 13 compression settings, ranging from 0 (heaviest compression) to 12 (best quality).

Select an option from the Quality pop-up menu or drag the slider triangle from 0 to 12 to specify the quality setting. Of the named options, Low takes the least space on disk but distorts the image rather severely; Maximum retains the highest amount of image quality but consumes more disk space. Of the numbered options, 0 is the most severe compressor and 12 does the least damage.

Next, JPEG divides the block by an 88 block of its own called the quantization matrix, which homogenizes the pixels' values by changing as many as possible to zero. This process saves the majority of disk space, but loses data. When Photoshop opens a JPEG image, it can't recover the original distinction between the zero pixels, so the pixels become the same, or similar, colors. Finally, JPEG applies lossless Huffman encoding to translate repeating values to a single symbol.

In most instances, I recommend you use JPEG only at the Maximum Quality setting (10 or higher), at least until you gain some experience with it. The smallest amount of JPEG compression saves more space on disk than any non-JPEG compression format and still retains the most essential detail from the original image. Figure 3-22 shows a grayscale image saved at each of the four compression settings.

Figure 3-22: Four JPEG settings applied to a single image, with the highest-image quality setting illustrated at the top and the lowest at the bottom.

The samples are arranged from highest image quality (top) to lowest quality (bottom). At the top left of each sample is the size of the compressed document on disk. Saved in the only moderately compressed native Photoshop format, the image consumes 8.92MB on disk. From 8.92MB to 1.34MB — the result of the lowest-quality JPEG setting — is a remarkable savings, but it comes at a price of significant compression artifacts. The effect, incidentally, is more obvious on screen. Believe me, after you familiarize yourself with JPEG compression, you can spot other people's overly compressed JPEG images a mile away. This isn't something you want to exaggerate in your images.

JPEG is best used when compressing continuous-tone images (images in which the distinction between immediately neighboring pixels is slight). Any image that includes gradual color transitions, as in a photograph, qualifies for JPEG compression. JPEG is not the best choice for saving screen shots, line drawings (especially those converted from EPS graphics), and other high-contrast images. These are better served by GIF if you want to post them on the Web or by a lossless compression scheme, such as TIFF with LZW. The JPEG format is available when you are saving grayscale, RGB, and CMYK images.

Occupying the bottom half of the JPEG Options dialog box are three radio buttons, designed primarily to optimize JPEG images for the Web. If your image is destined for print, just select the first option, Baseline ("Standard"), and be done with it. For Web graphics, select Baseline Optimized to make images display on screen line-by-line or select the Progressive option to make images display in multiple passes.

TIFF

Developed by Aldus in the early days of the Mac to standardize an ever-growing population of scanned images, TIFF (Tag Image File Format) is the most widely supported image-printing format across both the Macintosh and PC platforms. Unlike EPS, it can't handle object-oriented artwork, but otherwise it's unrestricted. In fact, TIFF offers a few tricks of its own that make it very special.

In Photoshop, the TIFF format supports up to 24 channels, the maximum number permitted in any image. In fact, TIFF is the only format other than DCS 2.0, "raw," and the native Photoshop format that can save more than four channels. To save a TIFF file without extra mask channels, deselect the Alpha check box in the Save dialog box. (For an introduction to channels, read Chapter 4.) Even more impressive, TIFF supports multiple layers. If you want layers to remain independent when you save the file, you can select the Layers check box in the Save dialog box.

When you save an image as a TIFF file, Photoshop displays the TIFF Options dialog box (see Figure 3-23), which offers the following controls:

Figure 3-23: Photoshop offers a myriad of compression schemes for TIFF files.

Compression: You can choose between three different types of compression: LZW (Lempel-Ziv-Welch), ZIP, or JPEG. Here are the major differences:

LZW: Like Huffman encoding (previously described in the "Saving an EPS image" section), LZW digs into the computer code that describes an image and substitutes frequently used codes with shorter equivalents. But instead of substituting characters, as Huffman does, LZW substitutes strings of data. Because LZW doesn't so much as touch a pixel in your image, it's entirely lossless. Most image editors and desktop publishing applications — including Illustrator, FreeHand, InDesign, PageMaker, and QuarkXPress — import LZW-compressed TIFF images, but a few still have yet to catch on.

ZIP: The problem with LZW (from a programming perspective) is that it's regulated by a patent. And whenever a bit of technology costs money to use, you can bet somebody out there is trying to come up with a free equivalent. Hence ZIP, a competing lossless compression scheme used in PDF documents. Why use it? Theoretically, it's a bit smarter than LZW and can on occasion deliver smaller image files. On the other hand, Photoshop is currently one of the few programs to support ZIP compression in a TIFF file. So unless you discover big savings when using ZIP, I'd stick with LZW until ZIP support becomes more widespread.

JPEG: If two lossless compression schemes aren't enough options, the TIFF format also permits you to apply lossy JPEG compression. Long-time Photoshop users may balk at JPEG compression inside TIFF options. After all, one of the major benefits of TIFF is that it ensures optimum image quality; by applying JPEG compression, which results in loss of image data, you defeat the purpose. But now that TIFF supports layers, JPEG inside TIFF permits you a unique opportunity to cut the size of your layered image files in half. My experience shows that JPEG in TIFF results in only a modest loss of data. And because JPEG does not affect the transparency mask — which defines the outlines of the layers — the layers continue to exhibit nice, sharp edges.

Byte Order: Every once in a while, Photoshop chooses to name a straightforward option in the most confusing way possible. Byte Order is a prime example. No, this option doesn't have anything to do with how you eat your food. Instead, there are two variations of TIFF, one for the PC and the other for the Mac. I'm sure this has something to do with the arrangement of 8-bit chunks of data, but who cares? You want PC or you want Mac? It's that simple.

There may be a hermit somewhere who has a stone TIFF reader that balks at this, but he probably can't run his 2-cycle-per-second wooden computer with Photoshop anyway!

Save Image Pyramid: Choose this option to save tiled TIFF files. This variation of the standard TIFF file-saving algorithm divides your image into tiles and then stacks the tiles in a pyramid. Each level of the pyramid represents your image at a different resolution, with the highest-resolution version serving as the base of the pyramid. The idea is that an application can use the low-resolution tiles to perform certain image-processing tasks and dig down to the high-resolution version only when absolutely necessary. When you're working with very large image files, this approach not only speeds up certain editing tasks but also puts less strain on your computer's resources. (If you're familiar with the FlashPix format, the concept is the same.)

Unless you're saving your image for use in a program that you know supports tiled TIFF images, however, turn this option off. Photoshop itself can't take advantage of the tiled technology, and many applications can't open tiled images at all.

Save Transparency: If the image contains transparent areas, select this check box to retain the transparency. Otherwise, transparent areas become white.

Layer Compression: Not only can you decide whether you want to use lossless or lossy image compression, but Photoshop lets you specify how you want to save the layers themselves. The choices speak for themselves; RLE saves more quickly but makes bigger files, and the reverse is true for ZIP. Alternatively, you can choose to discard the layers altogether and save a flattened copy of your file.

The oddball formats

Can you believe it? After plowing through a half-million formats, I still haven't covered them all. The last two are the odd men out. One format has a purpose so specific that Photoshop can open files saved in the format but it can't save to the format. The other is less a format than a manual can opener that may come in handy for jimmying open a file from an unknown source.

Photo CD YCC images

Photoshop can open Eastman Kodak's Photo CD and Pro Photo CD formats directly. A Photo CD contains compressed versions of every image in each of the five scan sizes provided on Photo CDs — from 128192 pixels (72K) to 2,0483,072 pixels (18MB).

The Pro Photo CD format can accommodate each of the five sizes included in the regular Photo CD format, plus one additional size — 4,0966,144 pixels (72MB) — that's four times as large as the largest image on a regular Photo CD. As a result, Pro Photo CDs hold only 25 scans; standard Photo CDs hold 100. Like their standard Photo CD counterparts, Pro Photo CD scanners can accommodate 35mm film and slides. But they can also handle 70mm film and 45-inch negatives and transparencies. The cost might knock you out, though. Scanning an image to a standard Photo CD costs between $1 and $2, but scanning it to a Pro Photo CD costs about $10. This goes to show you, as soon as you gravitate beyond consumerland, everyone expects you to start coughing up the big bucks.

Both Photo CD and Pro Photo CD use the YCC color model, a variation on the CIE (Commission Internationale d'Eclairage) color space, which I discuss in the next chapter. YCC provides a broader range of color — theoretically, every color your eye can see. By opening Photo CD files directly, you can translate the YCC images directly to Photoshop's Lab color mode, another variation on the CIE color space that ensures no color loss. When you open a Photo CD image, Photoshop displays the dialog box shown in Figure 3-24.

Figure 3-24: Use these options to select a resolution and to calibrate the colors in the Photo CD image.

The Photo CD dialog box is divided into three main sections: Image Info, Source Image, and Destination Image. The Image Info section simply tells you the type of film on which the image was shot and the type of scanner used to scan the image to CD. Selections that you make in the Source and Destination areas tell Photoshop how you want it to open the image. Here's what you need to know:

Pixel Size: Select which of the available image sizes you want to use from this pop-up menu.

Profile: Use this pop-up menu to select the kind of film from which the original photographs were scanned. You can select from one of the variations on Kodak's film brands — E-6 for Ektachrome or K-14 for Kodachrome — or settle for the generic Color Negative V3.0 Film option. Your selection determines the method Photoshop uses to transform the colors in the image.

Resolution: This setting determines the output resolution and size at which Photoshop opens the image. You get the same number of image pixels no matter what — that's controlled by the Pixel Size option. In other words, changing this value is no different than changing the Resolution value in the Image Size dialog box with Resample Image turned off.

Color Space: Select an option from this pop-up menu to specify the color model you want to use. Select RGB to open the image in the RGB mode; select LAB to open the image in the Lab mode. You can also select from 8 Bits/Channel to edit the image in 24-bit color or 16 Bits/Channel to open the image in 48-bit color.

Orientation: The preview in the left side of the dialog box shows you the original orientation of the image. If you want to change that orientation, click the other Orientation radio button. The preview updates to show you the new orientation.

Photoshop cannot save to the Photo CD format. And frankly, there's little reason you'd want to do so. Photo CD is strictly a means for transferring slides and film negatives onto the world's most ubiquitous and indestructible storage medium, the CD-ROM.

Opening raw documents

A raw document is a plain binary file stripped of all extraneous information. It contains no compression scheme, specifies no bit depth or image size, and offers no color mode. Each byte of data indicates a brightness value on a single color channel, and that's it. Photoshop offers this function specifically so you can open images created in undocumented formats, such as those created on mainframe computers.

To open an image of unknown origin on a PC, choose File Open As. On a Mac, choose File Open and select All Documents from the Show pop-up menu. Then select the desired image from the scrolling list and choose Photoshop Raw (*.RAW) from the Open As pop-up menu (or Format pop-up menu on the Mac). After you press Enter or Return, the Raw Options dialog box appears, featuring these options:

Width, Height: If you know the dimensions of the image in pixels, enter the values in these option boxes.

Swap: Click this button to swap the Width value with the Height value.

Count: Enter the number of color channels in this option box. If the document is an RGB image, enter 3; if it is a CMYK image, enter 4.

Interleaved: Select this value if the color values are stored sequentially by pixels. In an RGB image, the first byte represents the red value for the first pixel, the second byte represents the green value for that pixel, the third the blue value, and so on. If you turn this check box off, the first byte represents the red value for the first pixel, the second value represents the red value for the second pixel, and so on. When Photoshop finishes describing the red channel, it describes the green channel and then the blue channel.

Depth: Select the number of bits per color channel. Most images contain 8 bits per channel, but scientific scans from mainframe computers may contain 16.

Byte Order: If you specify 16 bits per channel, you must tell Photoshop whether the image comes from a Mac or a PC.

Header: This value tells Photoshop how many bytes of data at the beginning of the file consist of header information it can ignore.

Retain When Saving: If the Header value is greater than zero, you can instruct Photoshop to retain this data when you save the image in a different format.

Guess: If you know the Width and Height values, but you don't know the number of bytes in the header — or vice versa — you can ask Photoshop for help. Fill in either the Dimensions or Header information and then click the Guess button to ask Photoshop to take a stab at the unknown value. Photoshop estimates all this information when the Raw Options dialog box first appears. Generally speaking, if it doesn't estimate correctly the first time around, you're on your own. But hey, the Guess button is worth a shot.

Saving a raw document

Photoshop also lets you save to the raw document format. This capability is useful when you create files you want to transfer to mainframe systems or output to devices that don't support other formats, such as the Kodak XL7700.

When you save an image in the raw document format, Photoshop presents the dialog box shown in Figure 3-25. The dialog box options work as follows:

Figure 3-25: When saving a raw document on a Mac, enter the file type and creator codes and specify the order of data in the file.

File Type: This option defines information for the resource fork, so it's only pertinent to Mac folks. (Under Windows, the option is always dimmed. Feel free to ignore it.) Enter the four-character file type code (TIFF, PICT, and so on) in this option box. (You should check the documentation for the application you plan to use to open the raw document.) If you plan to use this file on a computer other than a Mac, you can enter any four characters you like; only Macs use this code.

File Creator: Again, this option is relevant only on a Mac. Enter the four-character creator code, which tells the system software which application created the file. By default, the creator code is 8BIM, Photoshop's code. Ignore this option unless you have a specific reason for changing it — for example, to open the image in a particular Macintosh application. (You won't hurt anything by changing the code, but you will prevent Photoshop from opening the image when you double-click the document icon at the Finder desktop.). On Windows machines, the 8BIM default code is selected for you and the option is dimmed.

Header: Enter the size of the header in bytes. If you enter any value but 0, you must fill in the header using a data editor, such as Norton Disk Editor.

Save Channels In: Select the Interleaved Order option to arrange data sequentially by pixels, as described earlier. To group data by color channel, select Non-interleaved Order.

Still can't get that file open?

File format specs are continually evolving. As a result, programs that provide support for a particular format may not support the specific version of the format used to save the file you're trying to open. For example, JPEG is notorious for causing problems because there were several private implementations in the early days. As a result, some JPEG files can be read only by the originating application.

If you can't open a file in Photoshop, you may have another program that can read and write the problem format. Try the problem file in every program you have — and every program your friends have. After all, what are friends for?

You may also want to try a program such as HiJaak, TransverterPro, DeBabelizer Toolbox, or DeBabelizer Pro from Equilibrium (www.equilibrium.com). Absolutely the best format converter bar none, DeBabelizer Pro handles every format Photoshop handles, as well as Dr. Halo's CUT, Fractal Design Painter's RIFF, the animation formats PICS, FLI, and ANM, as well as UNIX workstation formats for Silicon Graphics, Sun Microsystems, and others.

Still out of it? Go online and check out newsgroups such as comp.graphics.apps. photoshop and rec.photo.digital. Web-based forums such as the Creative Cow (www.creativecow.net) can also be a great resource. Post a question about your problem; chances are good someone will have an answer for you.