Note
The histogram is very useful in graphically indicating exposure, but its shape is of no artistic significance. The histogram may well indicate a perfect exposure of a perfectly horrible image.
If you intend to print in grayscale (i.e., black-and-white) you should nevertheless use RAW capture and, if possible, optimize the exposure as you would for color output. Full color high bit depth information will give you the flexibility to alter the grayscale rendering in a manner analogous to using different contrast filters when exposing film. In fact, with practice you can even go further, effectively using the equivalent of different filters for different parts of the scene. I can’t tell you how often I wanted to use a red filter on the sky (perhaps to increase contrast between blue sky and clouds), and use a green or yellow filter to lighten the foliage in the foreground, but of course I couldn’t do both in classical photography, so I chose the best option. Using channels, however, you can do something that’s equivalent to my wishes by printing each portion of the final print emphasizing the channel you want for each location. This can be grossly overdone (please refrain from going overboard), but if done with subtlety and sensitivity, it affords a wonderful set of controls.
The histogram is calculated in real time by the camera’s processor from a low resolution JPEG image, even if the camera is set to record only RAW files. Because the RAW data is recorded in high bit depth and receives only limited processing, the RAW capture is likely to contain more information in the highlights and shadows than is indicated in the histogram. All of the information contained in the RAW file can be extracted by the RAW converter discussed below.
Be aware that the histogram and, with some cameras the RAW file, may be affected by camera settings for contrast and sharpening, so you may find it desirable when working in RAW to dial down the setting for contrast and, if possible, turn off (or at least minimize) sharpening. If your camera has memory banks for retrieving camera settings, you will save time by setting one memory bank for your dialed down RAW captures, and another bank for your typical JPEG settings.
Keep in mind that while the histogram is very useful in graphically indicating exposure, its shape is of no artistic significance. The histogram may well indicate a perfect exposure of a perfectly horrible image. It simply tells you if the exposure is on target. Look to the end points for proper exposure; concentrate on compositional elements for artistic quality. Also realize that when you bias your exposures toward the right edge of the histogram, the camera display may appear washed-out. It’s best to ignore that appearance. You may want to make a second, darker exposure to show you a better rendition of the final image you’re after, but you’ll get better results from the washed-out exposure for final processing, unless you’ve clipped the right edge. But even that washed-out display can be useful for examining distractions at corners and edges, and evaluating overall compositional cohesiveness. You will later fix the washed-out rendering in the RAW converter with simple adjustments.
The RAW Converter—Processing the RAW Capture
The processing of the RAW data into an editable image format such as TIFF or PSD requires a number of operations, including demosaicing (de–mosaic–ing), which is the interpolation of the brightness information from each of the photosites into pixels containing red, green, and blue color data; the modification of the linear brightness response of the sensor to correspond to the response of the human eye; the proper rendering of color by setting of the white balance and the making of color corrections through the application of a camera profile; the correction of aberrations; the removal of noise; the increasing of edge contrast, known as sharpening, to compensate for losses resulting from the projection of the image through the camera lens onto the geometric array of photosites; and lastly the saving of the processed image in a recognizable format such as TIFF or PSD. All of these operations, and more, occur in a computer program that we refer to as the RAW converter. A brief explanation of each of the processes is discussed below.
RAW converter programs go by any number of names, many of which do not include the word RAW. Among camera manufacturers, Nikon publishes NX2; Canon publishes Digital Photo Professional; Sony publishes Image Data Converter; and Olympus publishes Olympus Master 2. In addition, there are standalone conversion programs including Adobe Camera Raw (ACR); Bibble 5 Pro, published by Bibble Labs; Capture One Pro, published by Phase One A/S; DxO Optics Pro, published by DxO Labs; LightZone, published by Light Crafts; and RAW Therapee, published by RT Team as shareware, to name but a few. Because the structure of the RAW file differs from one camera manufacturer to the next, indeed, sometimes from one camera model to the next, and because some manufacturers encrypt their RAW files, make sure the RAW converter you choose is compatible with your camera.
Predictably, each RAW converter program has its characteristics and each program has its preferred sequence of actions referred to as a workflow. Also, as digital technology evolves, software engineers include an ever-increasing number of features in their converter software. Most software publishers offer a trial version, so you can try a few before buying. As with photographic films, enlarging papers, and developers, every RAW converter has its ardent supporters as well as its detractors. Again, as with traditional photography, you’ll be best served by mastering the features of a limited body of software. For the discussion that follows, I’ll use the ACR converter common to both Lightroom and Photoshop. The user interfaces and controls of other converters will be different but the fundamental principals will apply.
In summary, all RAW captures require subsequent processing outside the camera in a RAW converter. Each RAW converter has its unique user interface, controls, features, and workflow, and each will render the RAW file differently, in much the same way that different film developers will produce negatives with different characteristic curves.
While the controls for each RAW converter vary, most allow you to zoom to the pixel level, preview the results of prospective changes as you readjust the settings, and permit you to make iterative adjustments. That is, you can go back and change earlier settings based on the results of subsequent settings, and you can make any number of revisions before clicking on the Open Image button. For the preservation of the RAW capture, be sure the processed file will be saved separately from the original—you want the original RAW file to remain unaffected and the converted file to be saved in TIFF or PSD format.
Figure 11-10. Image converted using Daylight white balance setting
We will look at a brief summary of each of the following operations that are available in a RAW converter:
Demosaicing