Digital offers so many new choices that it can be confusing at times. Remember what it was like when we first started photographing—our choices were befuddling then, too. We had no idea of what an ƒ-stop was or why we should choose a particular ƒ-stop and shutter speed combination. And what about depth of field versus selective focus?
Digital capture is similar—new things to learn that, once mastered, will be taken for granted. Sometimes, the choices aren't perfectly clear, like RAW and JPEG. Let's explore why RAW can be an important choice for many photographers, with ideas on getting the most from it.
I've covered JPEG and internal processing in cameras in the past because I felt there were many photographers who would be better suited shooting that way, yet the tech folks pushed RAW without consideration of how a photographer liked to work. Well-meaning experts often promote one approach to digital, but some photographers uncomfortable with that way lose some of their enthusiasm for our medium. If you get the results you want and need from high-quality JPEG, then keep doing it.
RAW is an extremely important tool for the digital photographer, however. There are three reasons why photographers should use it, I believe: they like processing images; they find limitations, causing them problems when shooting JPEG; and they need the increased flexibility RAW offers. RAW shouldn't be an automatic format to use because another photographer says so—that can lead to frustration in the time spent at the computer and when working with the RAW converter.
Once you decide to work with RAW, it's essential to understand that RAW requires a certain workflow to maximize its benefits. Many photographers now shoot RAW + JPEG so they get the best of both formats—a great way to go (especially since memory cards now offer a lot of megabytes with less cost). You gain the increased flexibility of RAW when you need it and the ability to work quickly with JPEG files when that's appropriate.
To use RAW to its best advantage, let's cover some basics. It certainly isn't a magic bullet that transforms any kind of exposure or lighting condition into a great shot. RAW is a type of image file with minimal change to the data coming from the sensor. It isn't unprocessed data as you may have read—the sensor creates analog information that must be processed into digital data. This is accomplished with the A/D converter and is a complex engineering challenge that, luckily, camera manufacturers have mastered for us.
A RAW file holds more tonal and color information than JPEG and offers a great deal of flexibility in how you can work the tones and color in an image. With RAW, you can frequently extract tones and details from the brightest and darkest areas of an image that have no detail in a JPEG file. In addition, image tonal qualities can be maintained throughout a greater range of adjustments done in RAW.
RAW allows you to enlarge digital images to a larger size with higher quality when done in the RAW converter than if you enlarge them later in Photoshop or using most other enlarging software. This can be remarkable, allowing superb-quality prints from even small digital files.There have been many misconceptions about RAW, however. One of the most common and unfortunate myths we hear is that RAW is so adaptable that you don't have to be as concerned about exposure or color since you can fix it in RAW.
The problem with such thinking is that it shortchanges RAW, creates more work to do in the computer (which can be frustrating) and can give you less than the best tonalities and color. Consider a couple of things: RAW comes from a sensor that has a finite range from black to white —if your exposure is outside of that range, nothing can bring it back, not even RAW; and RAW comes from a digital translation of analog information given by the sensor—GIGO (garbage in, garbage out) is definitely appropriate here. RAW does its best when it has good files from the start.
The key: Shoot it right in the first place. If you have any doubts, try another exposure. There's an idea that bracketing isn't ever needed with RAW, which could really shortchange you in a difficult lighting situation. Let's look at a few problems that come from poor photographic technique when shooting RAW.
Underexposure. The worst problem, if you underexpose a RAW file so that the tonal information is mostly in the dark areas (the left side of the histogram), you're not using the sensor most efficiently. When you brighten those dark areas, you don't have the best tonal or color information to begin with, plus you're brightening the most common place to find noise—dark areas. Even the best digital cameras will start showing annoying noise when an image has been underexposed. Remember, you always can darken a lighter exposure to keep noise out and colors in.
This is why you can't simply rely on your camera's LCD to tell if your exposure is correct. With a lot of practice comparing LCD images to what opens on your computer, you can judge images on the LCD, but a better practice is to learn to use the histogram. The overexposure warnings (or "blinkies") can help on exposure, but they can be misleading compared to the histogram.
If the warnings don't show up, there's a tendency among many photographers to think the exposure is okay when shooting with RAW when it could be underexposed. I've seen underexposed images from some pros that have distinct problems in the dark areas because they rely too much on these overexposure warnings.
Overexposure. Once you get excess exposure with too much of the histogram heading toward the right side, you also have tonal and color problems in later adjustments. You won't get added noise, but you'll get blocked-up, detail-less highlights that can be difficult or even impossible to deal with.
White Balance. Shooting on auto white balance won't cause any quality problems when shooting RAW, but it can create workflow issues. Auto white balance is very accurate today, but it can be fooled. I had a student on a trip to Peru who had a terrible time getting her camera to capture good color. Admittedly, she could correct that in RAW, but think of the disappointment from seeing images not quite right from a great location and the time required to "fix" photos later in the computer.
After suggesting that she use the custom white balance function of the camera, the images cleaned up nicely. Now she could review (and share with the group) photos that looked good immediately. In addition, she'd have less work to do on them when she returned home.
When you set a white balance in RAW, no pixels are harmed, but a tag of information goes with the file so that when it opens, it opens in the RAW converter with that white balance. You now have a specific point of reference to adjust from rather than the arbitrary and sometimes capricious white balance chosen by the camera.
Shooting it right for RAW can go beyond simple exposure. There's an excellent technique that helps in contrasty situations based on processing a RAW image twice (once for shadows, once for highlights), then bringing the two processed files together for a better overall tonal rendition than trying to process it all at once (see Linde Waidhofer's excellent article in the February 2004 issue of OP, "Expand Tonal Range Using A Single Image").
Sometimes a scene will have too much contrast for that technique, with tonalities beyond the capabilities of the sensor. Then you can expose twice while on location, exposing once for the shadows and once for the highlights. When in RAW, this technique offers an incredible amount of tonal and color detail that's impossible to capture in any other way. This will give tonal details like the old black-and-white masters achieved by using exposure and film developing to extend the negative's ability to capture brightness.
RAW has some amazing capabilities that only can begin to be discussed here. We'll come back to tips for processing the RAW file, but for now, just remember that RAW's full possibilities are enabled only when the image is thoughtfully exposed and captured by the sensor. RAW makes a good exposure better—and only means a lot of work with a poor exposure.
Editor Rob Sheppard's latest book is the PCPhoto Digital Zoom Camera Handbook, a guide to advanced digital cameras. He's leading a photo tour to Peru again this summer; visit the Palm Beach Photographic Centre website at www.workshop.org.