As we noted back in the Preface, this book only covers a fraction of the potential uses of Photoshopthose centered around production. People use this program for so many different things that we couldn't hope to cover them all here. In the last two sections, we discussed each of the file formats that are relevant for professionals who are putting images on paper, film, or the Web. You, however, might be doing something interesting, different, or just plain odd. Don't worry; Photoshop can probably still accommodate you.
While some of the following file formats appear in the Format popup menu in the Save As dialog box in the default shipping version of Photoshop, others are only available when you have loaded their plug-in from the Optional Plug-ins folder on the Photoshop or Creative Suite install discs (it's inside the Goodies folder).
Do you use Alias/Wavefront software for 3D rendering? Well, here's the file format for you: Photoshop can read the Alias .pix file format.
The Amiga computer story reads like that of the Tucker car or the PublishIt! desktop publishing software. Most people have never heard of these products, much less realized how great they were. Perhaps out of a sense of obligation to the would-be contender, or perhaps from a real need in the market (though we don't see it), Photoshop still lets you open and save in the Amiga IFF format. However, unless you really need it, or you want to see a format that features rectangular rather than square pixels, ignore it.
Kodak developed the Cineon file format for handling high-bit images (it's actually a 10-bit format). We're told Photoshop can open Cineon files, though we've never tried. Photoshop offers you the Cineon file format when you save a 16-bits-per-channel image. But as far as we can tell, Cineon is a dying format, so we don't bother with it.
ElectricImage is a powerful 3D rendering program. Photoshop can read these native files if you install the optional plug-in.
Video, film, and animation all have a similar popular appeal, and the tools that let mere mortals create this sort of stuff (like Adobe Premiere or iMovie) are everywhere these days. But that doesn't mean that programs that create or edit still images will go away. For what is video but a bunch of still images strung together over time?
Adobe Premiere and AfterEffects let you save movies in a file format that Photoshop can open, called Filmstrip. You can then edit each frame individually in Photoshop, save the file out again, and import the clip in the video/animation program. This technique not only lets you make small retouching changes, but even perform rotoscoping (a form of animation), colorizing, or any number of other special effects.
When you open a Filmstrip file in Photoshop, it looks like a tall and narrow noodle. But when you double-click on the Zoom tool to scroll in to 100-percent view, you can see each image frame clearly, along with its time and frame code. Note that changing the file's size, resolution, or pixel dimensions may be disastrous, or at least unpredictable. Instead, constrain your edits to the pixels that are already there.
HDR file formats
When you're dealing with High Dynamic Range (HDR) fileswhich use 32 bits per channelPhotoshop can read and write several additional file formats:
You can also save HDR files in the TIFF, Photoshop (PSD), Large Document Format (PSB), and Portable Bitmap (PBM) formats. We cover HDR in more detail in Chapter 12, Essential Image Techniques.
In the twilight years of the twentieth century, a bunch of smart folks got together to discuss the future of the JPEG file format. They came up with a new specification for JPEGlabeled JPEG 2000that does a better job of compressing images (more compression, less image degradation). Plus, unlike JPEG, JPEG 2000 can handle high-bit files, grayscale files, full 8-bit transparency, and even an option for lossless compression.
Unfortunately, just because there's a better format available doesn't mean people will rush to use it. As we go to press, no page-layout application can import JPEG 2000 files (though we assume the next version of InDesign will), nor can any Web browser display them without a specialized plug-in.
Nevertheless, always ahead of the curve, Photoshop can read and write JPEG 2000 files. Actually, it can read and write a flavor of JPEG 2000 it calls JPF. But it can only do so when you have installed the plug-in, found in the Optional Plug-ins folder, inside the Goodies folder on the Photoshop install disc. JPF files aren't compatible with most other JPEG 2000 software (which usually reads a flavor called JP2), but JPF offers more compression options than JP2, including the ability to JPF files compatible with JP2 readersat the expense of a slightly larger file size.
Once JPEG 2000 support is more widespread, we think this file format should replace the use of JPEG images in the prepress industry, where quality is key. (Note that we said it "should," as in "it ought to, if there's anyone out there who needs compressed files but still cares about quality.")
The MacPaint format is the most basic of all graphic formats on the Macintosh, but it's so outdated that there's almost no reason to use it anymore. Paint files (more rarely called PNTG, or "pee-en-tee-gee," files) are black and white (one bit per pixel), 72 pixels per inch, 8-by-10 inches (576-by-720 pixels). That's it. No more and no less.
Whereas many formats (such as TIFF) are industry standards, the PCX format was developed by ZSoft Corporation, the creators of Publisher's Paintbrush. It's a granddaddy of bitmapped formats, predating Windows 1.0 when it hit the streets as part of PC Paintbrush. The current version of PCX supports adjustable dimensions and resolutions, and 24-bit color, but only a 256-color palette (indexed to 24-bit color), up from earlier 4- and 13-color versions. We typically recommend using TIFF files instead of PCX whenever possible.
Portable Bitmap (PBM)
Some Unix tweaks save their images in the Portable Bitmap format (.pbm, .pgm, .ppm, or .pnm). Even HDR files can be saved in the PBM format.
To understand why Photoshop still saves and opens Pixar files, you have to understand that Photoshop was born from the minds of Thomas and John Knoll as a way to do some of the low-level grunt work that goes into the cool special effects produced at George Lucas's Industrial Light and Magic (ILM), which is a close cousin of Pixar. As far as we're concerned, someone should put this file format out of our misery.
David used Pixel Paint once, a very long time ago. On the odd chance that you have a Pixel Paint file sitting around, it's good to know that Photoshop can read it with the optional plug-in.
PSB (Large Document format)
While early versions of Photoshop limited your images to 30,000 pixels per side (2.5 GB), Photoshop CS lifted this to 300,000 pixels per side (a whopping 251 GB file). We only know of a handful of people who need this, including our friends in the intelligence community (who are reading this book over your shoulder right now), and our friend Stephen Johnson, who is using a scanning back camera to make hyper-resolution panoramas at 7,500 x 75,000 pixels each. While the native Photoshop file format still tops out at 30,000 pixels per side, you can save these truly huge files as TIFF files (up to 4 GB), Photoshop Raw files (not to be confused with Camera Raw), orthe best optionin the Large Document (PSB) format.
To save a PSB file, turn on the Enable Large Document Format checkbox in the File Handling panel of the Preferences dialog box. (Perhaps PSB stands for "Photoshop Behemoth"?) Then, choose Large Document Format from the Format popup menu in the Save As dialog box. PSB files support layers, effects, and any other Photoshop feature. However, they can only be opened in Photoshop CS or later.
PNG (Portable Network Graphic)
For a while there it looked like the GIF file format would take over the Internet, and therefore the world. Then, in early 1995, CompuServe and Unisys shocked the world by demanding that developers whose software wrote or read GIF files pay a royalty fee for the right to use the format. Legally, they were entitled; but no one had had to pay before, and it jarred the electronic publishing community enough that a group of dedicated individuals decided to come up with a new file format for Web graphics.
The result of their work is the PNG format (which is pronounced "ping," and officially stands for "Portable Network Graphic," though it unofficially stands for "PNG's Not GIF"). Not only is it a free format that any developer can use, but it does much more than GIF.
For instance, PNG can support both 8-bit indexed color and full 24-bit color. Where GIF can include 1-bit transparency (where each pixel is either transparent or not), PNG has full 8-bit transparency with alpha channels, so a graphic could be partially opaque in some areas. PNG also includes some limited ability to handle color management on the Internet, by recording monitor gamma and chromaticity. There are many other features, too (among which is the significant bonus of, unlike GIF, having a relatively unambiguous pronunciation).
Unfortunately, PNG has never been widely accepted by users or Web browsers, and the patents on GIF (which were based on GIF's LZW compression scheme) expired back in 2004. Our prediction is that PNG will slowly fade away over the next couple of years.
Are you authoring multimedia or developing software on the Macintosh? If so, you may find yourself needing to save an image into the resource fork of a file. Here's where the PICT Resource file format comes in. To be honest, it's not really a different file format; the Macintosh lets you place PICT information in the data or resource fork of a file. Photoshop, however, is a convenient way to move the image from one to the other. (Windows programs don't have a resource fork, so PC users can ignore this file format.)
Note that Photoshop lets you open PICT resources in two different ways. First, if the file has a PICT resource numbered 256, Photoshop lets you open that particular resource directly from the Open dialog box. If there are multiple PICT resources, you can access them only by selecting PICT Resource from the Import submenu (under the File menu).
The last file format that we can even remotely recommend using is the file format of last resort: the Raw format. (Don't confuse this with the Camera Raw format, which Photoshop can read but not write. See Chapter 11, Building a Digital Workflow, for more on Camera Raw.) If you've ever traveled in a foreign country, you've probably found yourself in situations where you and the person in front of you share no common language. The answer? Reduce communication to gestures and sounds.
The Raw format is a way to read or write image data in a "language" that Photoshop doesn't know. It relies on the basics of bitmapped images (see Figure 13-12).
Figure 13-12. Opening Raw data
If you're trying to import from or export to some strange computer system, you may have to rely on the Raw format because that system might not know from TIFF, EPS, or any other normal, everyday file format. This is becoming less of a problem as most mainframe systems (especially the imaging systems that are used for scientific or medical imaging) learn the newer, better file formats we've been discussing up until now.
Note that Photoshop can only read data using the Raw data format if it's saved as binary data; hexadecimal is out.
Tip: Make Photoshop Guess for Raw Data
Okay, someone gives you a file and you find you can't open it using any of Photoshop's standard file format options. You decide to take a leap and attempt the Raw format. But when you ask your so-called friend about the file's vital signs"What are the pixel dimensions? Interleaved or noninterleaved color? Is there a header?"he just stares at you blankly.
Fortunately, Photoshop can do a little guessing for you. If you click the Guess button in the Open as Raw dialog box when the Width and Height fields are blank, Photoshop figures out a likely height/width combination for the image. If it's a color image, you need to know if it's RGB (three channels) or CMYK (four channels).
If there's a header and your friend doesn't know how big it is (in bytes), then it's probably a lost cause. On the other hand, if your friend knows the pixel dimensions but not the header, you can click the Guess button while the Header field is blank.
Wavefront software can also export in the .rla file format, which Photoshop supports.
Whether to use the Scitex CT file format is a no-brainer: if you own a Creo Scitex system or are trying to output via a Scitex system, you may want to save your document in this format as the last stage before printing. If you don't have any contact with a Creo Scitex system, ignore this one.
It may be important to note that the Scitex CT format is not actually the CT ("continuous tone") format that Scitex folks usually talk about. It's actually the Handshake format, which is less proprietary and more common (even QuarkXPress can import these files). Scitex CT files are always CMYK or grayscale; however, Photoshop lets you save RGB images in this format, too. We don't know why. If you can figure out a good use for them, let us know.
Yes, the SGI in the name SGIRGB is the SGI of the SGI computer company. We just like typing SGI. But we don't use this format. If you do, just make sure your files have one of these file name extensions: .sgi, .rgb, .rgba, or .bw.
Here's one last 3D rendering software format. Photoshop can read SoftImage files, for those who need that sort of thing.
The Photoshop manuals maintain that the Targa file format is designed for TrueVision video boards, though other programs (especially DOS programs) also use it. Like Pixel Paint, this format is almost entirely obsolete, as far as we can tell (though it lingers on in some mainframe and minicomputer databases).
Photoshop pictures go everywhere these days, as big as billboards and as small as little icons on cell phone screens. If you're trying to make pictures for cell phones and wireless PDAs, we've got just the file format for you: WBMP. You can save files that are already in Bitmap mode as WBMP format from the Save As dialog box, or any file as WBMP from the Save For Web dialog box (see Chapter 14, Multimedia and the Web).
Windows Bitmap (BMP)
Windows Bitmap (typically called "BMP," pronounced by saying the letters) is the bitmap format native to Windows Paint. It's rarely encountered outside of Windows and OS/2 Presentation Manager, and is hardly a professional's file format. You can store a 1-, 4-, 8-, or 24-bit image of various dimensions and resolutions, but we still prefer TIFF, given its strong support by desktop-publishing applications and compatibility across different computer systems. If you're creating wallpaper for your Windows desktop, this is the format for you!