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RAW Pros and Cons
The reason you need special software to turn a RAW file into something most imaging programs can read is that every camera maker -- indeed, every camera model -- has its own, proprietary RAW format. There are roughly 100 RAW formats, and counting. Each camera company provides the necessary proprietary conversion program; some are free and others cost extra, and they're not all created equal. There are also third-party RAW-conversion programs, the most popular and well-known of which is Adobe Camera Raw. Built into Photoshop CS/CS2 and Photoshop Elements, and available as a plug-in for Photoshop 7, this application is updated several times a year to accommodate the latest cameras. Photoshop CS2 reads the RAW files of virtually every model introduced in the past six years. Other popular programs include Capture One from Phase One, Bibble from Bibble Labs, and RawShooter from Pixmantec. The first three are available for both Windows and Mac platforms, while RawShooter is PC-only.
Whichever software you choose, as soon as you open a RAW file it automatically translates the original monochrome data into color and applies a gamma tone curve to brighten what otherwise would be a very dark image if left uncorrected. (This is called de-linearization.) It also reads and applies the camera settings you used when you took the picture. With RAW, though, those settings are just a starting point: From there you can change almost any image characteristic to suit your needs and tastes. These include highlight and shadow points, color balance, brightness and contrast, saturation, sharpness, and digital noise reduction.
Once you've made all those adjustments, you can output the file to a variety of standard image formats. The most common choices are TIFF (Targeted Image File Format) and PSD (the native Photoshop format). Like RAW, these formats are lossless, meaning that you can open and save the image any number of times without degrading quality. Even more important, they allow you to work in 16-bit color mode, which holds the full 12-bit data contained in the original RAW file. You can also save a RAW file as a JPEG, but I'd recommend this only for specific uses such as e-mailing, posting on a Website, or saving to a CD (or other storage medium) that will be viewed and possibly used by others. I would avoid JPEG if you plan to do further, substantial image editing.
The work involved in processing a RAW file is more time-consuming than simply opening a regular JPEG in Photoshop. But the advantages of editing an image within the RAW environment are, in my opinion, more than worth the effort. Why? First, because the process is non-destructive. Regardless of the changes you make, the original RAW data is left completely intact, and you can always return to your initial settings. Second, since a RAW file has no embedded white balance, you can adjust color temperature without degrading the picture in any way. For example, a daylight scene mistakenly photographed with a tungsten white-balance setting can be corrected in the RAW software. But a JPEG with the wrong white balance cannot be fixed properly.
The third and, arguably, the biggest advantage of RAW is that it gives you 12 bits of brightness data to work with, both in the RAW software itself and when you save the file to a 16-bit TIFF or PSD. Those 12 bits translate to 4,096 discrete levels of brightness -- 16 times the 256 levels available in a JPEG's limited eight-bit space. This is critical if you need to alter brightness in any significant way.
The two darkest exposure zones in a 12-bit RAW file contain 384 levels of brightness; in the eight-bit JPEG, only 47 levels. If you decide to open up those shadows in a JPEG, you'll end up with abrupt jumps between the brightness levels. These appear as visible gaps in the histogram display. But an identical adjustment to the RAW file will cause no problems, because there are more than enough levels to ensure smooth transitions.
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