Although JPEG is the standard format used by cameras, there's another option that's becoming quite common. All interchangeable-lens cameras and the better digicams also allow for Raw capture. If your camera provides this mode, read on, because you'll want to use it for your most important photos.

How It Works

In Raw capture mode the camera records raw data from the sensor in a special format such as Nikon's NEF. Your in-camera settings for white balance, exposure compensation, contrast, sharpening and colour saturation are recorded, but they are not locked into the image data. After you download the Raw photos to a computer, all of these settings can be retained; or they can be modified using the special software bundled with the camera. (Other programs, including some from Adobe, can also be used.) When the photo looks just right, convert it to a familiar format, preferably TIF.

Hint: TIF is a better format than JPEG for use in a computer. A JPEG must be re-compressed each time you modify and close it, with an additional loss of data. However, the compression used for a TIF is "lossless." There's no detectable loss of quality caused by the process.

The Primary Benefits

A Raw photo provides the absolutely best quality a camera can produce. When you shoot a JPEG, data is lost when it's saved to the memory card. That's because the compression process discards pixels in order to save the photo in a small JPEG file. Later, when you open the JPEG in a computer, your software adds pixels to rebuild the file, so it's returned to the full size. Problem is, the process is not perfect. There will always be some loss of image quality, although it won't be serious if you used the Fine JPEG option.

While a Raw file may also be compressed, that process is "lossless": the change in image quality will be undetectable. But there's another reason for shooting in the Raw format. A Raw file offers much greater latitude for correction of many aspects. In other words, many changes can be made in the converter software without damaging the photo (this is called a non-destructive process). This can be useful for correcting technical problems.

Let's say you were shooting under sodium-vapour lighting with Auto White Balance, and your images all exhibit a strange colour cast. Or perhaps you were shooting a light-toned scene (such as a snowy landscape) and many of your images are underexposed. Or you might have set the colour saturation level to High in-camera, and skin tones are much too ruddy. That's not a problem if you were shooting in Raw mode, since all those aspects (and many others) can be modified in the converter software. While intense changes will still cause some damage to the pixels, more typical modifications will produce minimal problems.

Of course, photos that were made in JPEG capture can also be corrected or enhanced with common image-editing programs. When the changes that you must make are small, and few, the damage to the pixels may not be noticeable unless you make a very large print. However, it can be impossible to properly correct major problems without seriously degrading JPEG image quality. This applies even if you convert your JPEGs to TIF before working on them in software. No conventional image format is as resilient as Raw.

The Drawbacks

In spite of the benefits, it's unlikely that you'll use Raw capture for every shot. The files are larger than JPEGs and that can slow the recording time, a problem in action photography, for example. They can also quickly fill up your memory card and they will consume a lot more space in your computer. Finally, you'll need to spend extra time at a computer, enhancing the raw data and converting the files to TIF. When you return from a trip with hundreds of photos, that can be extremely time consuming.

The Bottom Line

Unless you're a fanatic about the quality of every shot, you'll probably shoot Large/Fine JPEGs most of the time. Use in-camera overrides such as exposure compensation and the white balance options to minimize technical problems. This approach will provide very good image quality in-camera and you won't need to make many damaging changes to your photos with software. But when you absolutely must be sure of getting a perfect image, switch to Raw capture mode and take advantage of its significant benefits. Use it particularly for important events, or once-in-a-lifetime photo opportunities and you'll have extra peace of mind.

Photo Caption: When taking photos that are very important, it's worth switching from JPG to Raw capture mode. A Raw file will retain the best possible image quality in the camera and later when you modify technical aspects with computer software. (Adobe Camera Raw screen) (c) 2009 Peter K. Burian

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