Bruce Barnbaum - The Art of Photography - An Approach to Personal Expression

Figure 11-15 shows the image as adjusted with the Exposure and Recovery values used in Figure 11-14 with the Blacks value increased from the default setting of 5 to 20. Note how the darker areas of the image have been lowered in value and the overall contrast of the image has been increased. The spike at the left edge of the histogram reflects the pure black pixels in the image.

Lastly, the display of your work, whether it is backlit as on a computer display or reflective as with an inkjet print, will influence the appropriate setting of the black and white points in an image. Backlit displays will reveal details in deep shadows that would be lost in an inkjet print. Similarly, highlight tonalities will appear different depending on whether they are backlit or reflective. Indeed, prints may need to be adjusted for different viewing conditions. Observation of your work under various lighting conditions will soon give you the judgment to relate the appearance on the computer display, and the numerical data from your software’s color sampler, to your intended form of output. It will prove to be of great help to use the eyedropper tool in Photoshop as a densitometer to correlate the image on the screen to your output, and this will be particularly useful for printed output.

In practice, try all of the controls, observe the image as you change settings, and remember that you can keep changing the settings until you get the result you desire. In other words, play around with it. Toggle the triangles in the upper left and right hand corners of the histogram on and off to display any areas of underexposure and overexposure. See what you can and can’t do. Experiment. Only when you tell the program to Open Image (or Save Image) will the settings be applied and the results be saved as a converted image.

In addition to using the Exposure, Recovery, and Blacks sliders in ACR, after you convert the RAW file you can fine tune the settings in Photoshop using either a Levels or Curves layer. To illustrate using Curves, first, create a new Curves layer: From the Layer menu select New Adjustment Layer and choose Curves. Photoshop will prompt you for a name for the new layer. Insert a descriptive name such as Global Contrast, and click OK. The Curves palette will open and present both the histogram and a default straight line curve. At the lower left of the histogram is a black triangle that sets the black point of the image. Moving the black triangle to the right forces darker pixels to pure black. Hold the Option/Alt key down and slide the black triangle to view the portions of the image that will be rendered pure black. Similarly, at the lower right of the histogram is a white triangle that sets the white point of the image. Moving the white triangle to the left forces brighter pixels to pure white. Hold the Option/Alt key down and slide the white triangle to view the portions of the image that will be rendered pure black. While you have the Curves layer open, you can adjust the overall appearance of the image by altering the curve.

Correcting Aberrations

The projection of the scene through your camera lens onto the photosite-CFA induces a number of undesirable effects including color fringing, vignetting, the introduction of noise, and loss of sharpness. RAW converters have a number of tools for the correcting of aberrations. Using a high quality, calibrated monitor, zooming in to 100% magnification, and having a uniformly lighted viewing environment will aid you in correcting your RAW conversions.

The uniformity of the viewing environment (i.e., the ambient lighting where you view your computer monitor) is critical, for if your ambient lighting changes throughout the day and night, you can’t tell with any degree of precision what you’re working with. You’re playing a game with movable boundaries. So, if your monitor sits adjacent to an open window, things look quite different on a sunny day, a cloudy day, at night, or under any other set of changing conditions. If you’re serious about obtaining the best possible images, you must create an environment where the lighting remains constant whenever you’re working.

Note

If you’re serious about obtaining the best possible images, you must create an environment where the lighting remains constant whenever you’re working on your computer .

In ACR, the Lens Corrections tab includes sliders to correct for color fringing and for lens vignetting. The Sharpening tab contains the settings for noise reduction. The Camera Calibration tab is the place to import and apply any custom camera profile you may have and to fine-tune the color rendering in each of the color channels. Move the sliders and study the results. When you have arrived at a group of settings that gives consistently good results with your camera-lens combination, you can save the settings for each tab in ACR and apply the settings automatically to any number of captures taken with the same camera and lens.

Typical of ACR, the settings are not applied until the image is processed, so you can go back and forth between settings and tabs if necessary, and your custom settings can be saved and recalled for reuse.

Sharpening the Capture

One area of image correction that deserves particular attention is that of sharpening. Each step in the process from capture to print causes a degradation in the sharpness of the image. The fix is what is referred to as sharpening and works by increasing the local contrast along the boundaries between lighter and darker portions of the image. In theory, the software finds edges (the boundaries between lighter and darker areas) and then darkens the darker side and lightens the lighter side of the edge. In practice, what Photoshop registers as an edge may simply be an area of local contrast where you do not want to exaggerate tonal differences. To be effective, sharpening must be strong enough to carry the illusion of sharpness but not so strong as to create undesirable halos or visible outlines, introduce granularity in areas of more or less smooth tonalities, or worse yet, pucker skin tones. Not surprisingly, the difference between effective sharpening and oversharpening is often small, leading to the truism: sharpen but don’t oversharpen.

Common practice is to perform sharpening in two stages. First, do a modest sharpening in the RAW converter to produce a realistic presentation with which to do your editing, and then do a second, output sharpening just before printing. Every photographer has his or her approach to sharpening and you will acquire your own.

To get started with sharpening in ACR, you will find the sharpening controls under the Detail tab. Zoom in to view the image at 100 %. To see the affect of your changes, first exaggerate the Amount setting, then refine the Radius and Detail sliders. As a rule, images with predominately fine detail (e.g., pine needles on the ground, old wood on an abandoned building, stonework inside a cathedral, etc.) often look best with a small radius setting such as 0.7–0.8, and images with areas of smooth texture (e.g., skin tones, lightly rippled water, smooth surfaces like concrete) often look best with a radius setting of 1.2–1.4.

Next adjust the Masking slider to confine the sharpening to the true edges. Increasing the masking slider restricts the sharpening to tonal differences that are more likely to be edges. If you want to view the mask as you make changes to the Masking setting, hold down the Option/Alt key and move the Masking slider. The black areas are masked and will not be sharpened; the white areas are treated as edges and will be sharpened. Finally, dial down the Amount until the overall effect is barely visible when viewed at 100 %. Use the preview checkbox to toggle between the sharpened and unsharpened versions. Refine as needed but resist any temptation to oversharpen. Depending on your camera, your computer display, and a number of other variables, you may find you need to increase or decrease the Amount. As you gain experience with different subject matter, you will acquire the judgment to sharpen any number of RAW captures of similar subject matter. You can save and recall the sharpening settings you routinely use.