Weighing the pros of Raw
Talk to just about any professional digital photographer these days, and you’re sure to hear about the wonders of shooting in Raw mode. This feature, typically found in high-end cameras and digital SLRs, gives you much more control over a photo’s tones and details. But it has its drawbacks. Before jumping on the bandwagon, make sure you know how to put this format’s strengths to best use.
Raw versus JPEG
When you press the shutter button in JPEG mode, the camera’s sensor captures the image data and passes it to an onboard computer, which processes the data into a full-color image. The computer then applies the saturation, contrast, sharpening, and other image settings you’ve defined in your camera’s menus. Finally, it compresses the image into a JPEG file—discarding some of the original image data in the process—and stores it on your media card.
Now, compare that to what happens when you take a picture in Raw mode. (Not all cameras feature a Raw mode. If yours does, you’ll find it under the same camera menu as your JPEG quality settings. You may have to switch to one of your camera’s manual shooting modes to access it.) When you press the shutter button in Raw mode, the camera’s sensor captures the image data and stores it on the media card. That’s it. The camera doesn’t do any image processing or compression—you end up with raw, unprocessed data.
The upside to Raw
Skipping the processing step gives Raw files several advantages over their JPEG counterparts.
Delayed Decisions While many cameras do a very good job of processing JPEGs, the image adjustments aren’t reversible. So if your camera applies too much sharpening, you’re stuck with it. Similarly, if your camera tends to oversaturate or shift colors, removing these effects afterward can be very difficult.
Highlight Recovery The blown highlights in the image’s clouds might have made it fodder for the Trash if I had taken it in JPEG mode. But with Aperture’s highlight recovery features, I was able to recapture most of the details.
But with a Raw file, you can delay these image-processing decisions until you’re in front of your computer. That means you stand a better chance of getting an image that looks just the way you want. For instance, you’ll never end up with a Raw file that has bad white balance.
More Image Data Though the image sensors in most digital cameras capture 10 or 12 bits of data per pixel, JPEG files can store only 8 bits of data per pixel. So your camera has to throw out a fairly significant amount of color data. Although you can process Raw files as 8-bit images, you can also process them as 16-bit images, thus preserving all the color data your camera has captured. With this extra color data on hand, you can make large image adjustments—such as broad levels or saturation changes—without seeing banding or splotchy patterns.
No Compression The type of compression used to create a JPEG file can degrade your image by creating blocky artifacts and patterns. While your images may look fine right out of the camera, you’ll have to ensure that your workflow doesn’t apply additional compression.
The downside to Raw
Of course, the Raw format also has its disadvantages.
Larger Files, Slower Speeds Because the data is uncompressed, Raw files are much larger than their JPEG counterparts (though smaller than the TIFF files some cameras capture), which means that you’ll need more camera storage while shooting, as well as more disk space for editing and archiving. Also, your camera may require more time to write these large files to its media card. Depending on the camera, it may not shoot as many images in a single burst.
Additional Processing The JPEG format is now a universal standard. You can take the images out of your camera and immediately open them up in an image editor, a cataloger, and even most e-mail programs. When we talk about Raw files, we’re not referring to a single, standardized file format, such as JPEG or TIFF, but rather to each camera’s proprietary data format. To work with these files, you need software that understands the camera’s imaging characteristics and can accurately convert its unprocessed data into an image. This step is further complicated by the fact that different software may process the same Raw data in different ways.
This reliance on third-party software once posed a serious drawback to shooting in Raw mode. But recently, a flood of apps has made working with Raw files as easy as using JPEGs (see “Choosing a Raw Converter” on the next page). In fact, Apple built a Raw converter into OS X 10.4. However, you must make sure that the software you choose supports the particular camera model you have—whether it’s an old or a brand-new camera.
Shoot for the Shadows Raw files store far more information for bright tones than for dark ones. While film photographers are used to underexposing to protect their highlights, it’s actually better to err on the side of overexposing when shooting in Raw mode. Software such as Aperture and Adobe Camera Raw can recover some of the highlights while also darkening the midtones to rebuild the shadows. This results in shadows with less noise than you would see if you had underexposed your images.
Knowing when to go Raw
In most cases, you’re best served by matching the camera’s shooting mode to the situation. For quick snapshots that you don’t want to spend a lot of time editing, there’s no advantage to shooting in Raw mode. But if you’re taking shots that you need to get just right, or if you’re dealing with a tricky lighting situation, Raw files offer the greatest flexibility. They’ll also give you more image data, which may be important if you plan to make large prints or dramatic tonal changes.
Thankfully, deciding to shoot in Raw mode isn’t an irreversible commitment. You can switch freely between Raw and JPEG modes as the situation warrants. Some cameras even offer a Raw + JPEG mode that writes out both types of files with each shot, giving you the best of both worlds.
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