Using Camera Raw

This chapter is from the book

Real World Camera Raw with Adobe Photoshop CS

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This chapter is from the book

This chapter is from the book 

Real World Camera Raw with Adobe Photoshop CS

Learn More Buy

Camera Raw Image Controls

The image controls—the ones you're likely to change with each image—occupy the rest of the Camera Raw dialog box. In Basic mode, they're split into two tabs, Adjust and Detail. Advanced mode adds two more tabs, Lens and Calibrate, that provide additional controls for the more advanced user. You can toggle quickly between the tabs by pressing Command-1 through Command-4.

These controls are really the meat and potatoes of Camera Raw, offering very precise control over your raw conversions. Some of the controls offer functionality that simply can't be replicated in Photoshop, while with others, the difference between making the adjustments in Camera Raw or in Photoshop is a little less clear-cut, depending to some extent on what you do with the controls that Photoshop can't replicate.

The Adjust Tab

The controls in the Adjust tab let you tweak the white balance, exposure, tonal behavior, and saturation. Three controls in this tab are key: the Temperature, Tint, and Exposure controls let you do things to the image that simply cannot be replicated using Photoshop's tools on the converted image.

The Contrast, Brightness, and Shadows controls provide similar functionality to Photoshop's Levels and Curves, with the important difference that they operate on the high-bit linear-gamma data in the raw capture, rather than on gamma-corrected data post-conversion. If you make major corrections with the Exposure slider, you definitely want to use the Brightness, Contrast, and Shadows controls to shape the raw data the way you want it before converting the raw image. If you don't make big Exposure corrections, it's more a matter of convenience whether you do the major tone-shaping in Camera Raw or in Photoshop.

The Saturation control in Camera Raw offers slightly finer global adjustments than Photoshop's Hue/Saturation command, but unlike the Photoshop command, it doesn't allow you to address different color ranges selectively. See Figure 3-14.

Figure 3-14 The Adjust tab

White Balance

The two controls that set the white balance, Temperature and Tint, are the main tools for adjusting color in the image. If your camera's response to light is reasonably close to the one used to build the profile support for the camera model, then when you set the white balance correctly the rest of the color should more or less fall into place in terms of hue. Note that "correct white balance" includes, but isn't limited to, "accurate white balance." Later in this chapter I'll show some creative uses of the white balance controls.

If you find yourself consistently making the exact same selective color corrections in Photoshop on your processed raws, you may want to visit the Calibrate tab to tweak the color for your specific camera—see "The Calibrate Tab," later in this chapter.

• Temperature. The Temperature control lets you specify the color temperature of the lighting in Kelvins, thereby setting the blue-yellow color balance. Lowering the color temperature makes the image more blue to compensate for the yellower light; raising the color temperature makes the image more yellow, to compensate for the bluer light. (This may seem counterintuitive—we're used to thinking of higher color temperatures as bluer and lower ones as yellower: the trick is to remember that the temperature control compensates for the color temperature of the light, so if you tell Camera Raw that the light is bluer, it makes the image yellower.)When the Temperature field is selected, the up and down arrow keys adjust the color temperature in increments of 50 Kelvins. Adding Shift adjusts the temperature in increments of 500 Kelvins.
• Tint. The Tint control lets you fine-tune the color balance along the red-green axis. Negative values add green, positive ones add red. The up and down arrow keys change the tint in increments of 1. Adding Shift changes the tint in increments of 10.Figure 3-15 shows an image as shot, and the same image with some fairly gentle white balance adjustments that nevertheless greatly alter the character of the image. Notice that the adjustments involve the use of both the Temperature and Tint sliders. Later in this chapter, I'll look at more extreme uses of white balance adjustments.
  

  Figure 3-15 White Balance adjustments

Note that you can alter the color balance dramatically with these controls with virtually no image degradation, which you simply can't do on the converted image using Photoshop's tools. Camera Raw's controls alter the colorimetric interpretation of the image in the conversion to gamma-corrected RGB, while Photoshop's Color Balance and Photo Filter features actually stretch or squeeze the levels in individual channels. Compared to making color balance changes in Photoshop, doing so in Camera Raw is almost lossless.

Tone controls

Learning how the four tone controls, Exposure, Shadows, Contrast, and Brightness, interact will save you time. They aren't particularly intuitive at first glance, but the four controls work together to produce a five-point curve adjustment.

Exposure and Shadows set the white and black endpoints, respectively. Brightness adjusts the midpoint. Contrast then applies an S-curve around the midpoint set by Brightness, darkening the values below the midpoint and brightening those above, without affecting the endpoints. Figure 3-16 shows the tonal adjustments translated, approximately, into Photoshop Curves.

Figure 3-16 Tonal adjustments

If you use significant negative Exposure adjustments, the logic of the tonal controls changes somewhat, because extended highlight recovery tries to undo some of the highlight compression applied by the Brightness slider, but the same general principles still apply.

• Exposure. The Exposure slider controls the mapping of the tonal values in the image to those in your designated working space, but it's first and foremost a white-clipping adjustment. Remember—half of the captured data is in the brightest stop, so Exposure is a highly critical adjustment!

  Large increases in exposure value (more than about 0.75 of a stop) may increase shadow noise and possibly even make some posterization visible in the shadows, simply because large positive exposure values stretch the relatively few bits devoted to describing the shadows further up the tone scale. If you deliberately underexpose to hold highlight detail, your shadows won't be as good as they could be.

  The Exposure control also allows you to recover highlight information from overexposed images. For the technical details behind highlight recovery, see the sidebar "How Much Highlight Detail Can I Recover?" in Chapter 2, How Camera Raw Works; for a practical hands-on look at highlight recovery, see the second image in the continuation of Figure 3-35 on page 86, later in this chapter.

  

  Figure 3-35 Setting Exposure

  When the Exposure field is selected, the up and down arrows change the exposure in increments of 0.05 of a stop. Adding Shift changes the exposure in increments of 0.5 of a stop.

• Shadows. The Shadows slider is the black clipping control. It works very like the black input slider in Photoshop's Levels, letting you darken the shadows to set the black level. But the Shadows control operates on the linear-gamma data, so small moves tend to make big changes compared to using the black input slider in Levels, at least in the current version (2.2) of Camera Raw. Hence caution is required—I usually leave a little headroom so that I can fine-tune the black clipping in Photoshop on the converted image. One planned enhancement to Camera Raw is to make the Shadows slider a little gentler, but it will remain first and foremost a black-clipping tool.When the Shadows field is selected, the up and down arrow keys change the shadows in increments of 1. Adding Shift changes the shadows in increments of 10.

  TIP

  Use the Clipping Display in Exposure and Shadows. For years, I've relied on the threshold clipping display in Levels to show me exactly what's being clipped in each channel as I adjust the black and white input sliders. Camera Raw offers the same feature for the Exposure and Shadows sliders (I wish it offered it for Saturation, too). Hold down the Option key as you move the Exposure or Shadows slider and you'll see the clipping display. White pixels indicate highlight clipping, black pixels indicate shadow clipping, and colored pixels indicate clipping in one or two channels. See Figure 3-17.

  

  Figure 3-17 Camera Raw clipping display

• Brightness. Unlike its image-destroying counterpart in Photoshop, Camera Raw's Brightness control is a non-linear adjustment that works very much like the gray input slider in Levels. It lets you redistribute the midtone values without clipping the highlights or shadows.The up and down arrow keys change the brightness in increments of 1. Adding Shift changes the brightness in increments of 10.
• Contrast. The Contrast slider applies an S-curve to the data, while leaving the extreme shadows and highlights alone. Increasing the Contrast value from the default setting of +25 lightens values above the midtones and darkens values below the midtones, while reducing the Contrast value from the default does the reverse.The up and down arrow keys change the contrast in increments of 1. Adding Shift changes the contrast in increments of 10.

Saturation

The Saturation slider acts like a gentler version of the Saturation slider in Photoshop's Hue/Saturation command. It offers somewhat finer adjustments than Hue/Saturation; but a Hue/Saturation Adjustment Layer allows you to fine-tune by varying the layer opacity, so as with Shadows, Brightness, and Contrast, it's pretty much a wash whether you make the adjustments in Camera Raw or in Photoshop. The up and down arrow keys change the saturation in increments of 1. Adding Shift changes the saturation in increments of 10.

Figure 3-18 shows a normally exposed image as shot, and a typical set of adjustments that we might make in Camera Raw's Adjust tab. I'll look at the fairly complex interaction of the Exposure, Shadows, Brightness, and Contrast controls on more difficult exposures a little later in this chapter.

Figure 3-18 Basic Camera Raw adjustments

The Detail Tab

The sliders in the Detail tab let you apply global sharpening and reduce noise in both luminance and color (see Figure 3-19). To use these controls effectively, you need to zoom the preview to at least 100%—often 200% or higher is more effective. The up and down arrow keys move the sliders in increments of 1. Adding Shift moves the sliders in increments of 10.

Figure 3-19 The Detail tab

Most cameras need some amount of color noise reduction regardless of ISO speed. Each camera vendor makes its own compromise between image softness and color artifacting—if an image detail falls on only a red, only a green, or only a blue pixel, the demosaicing algorithm has to make some guesses to figure out what color the resulting image pixel should really be, and sometimes single-pixel color artifacts result. Color noise reduction can also eliminate rainbow artifacts in highlights and green-magenta splotches in neutral grays.

The need for luminance noise reduction tends to be more dependent on ISO speed and the image content.

Sharpness

The Sharpness slider lets you apply a variant of Unsharp Mask to the preview image or to both the preview and the converted image, depending on how you set Camera Raw Preferences (see "The Camera Raw Menu," earlier in this chapter). Unlike Unsharp Mask, Camera Raw's Sharpness only offers a single control—the Threshold value is calculated automatically based on the camera model, ISO, and exposure compensation values reported in the image's metadata.

I find the Sharpness control a bit of a blunt instrument, and for images that will receive more than cursory attention, I either set the slider to zero or, more likely, set the Preference so that Sharpness only applies to the preview. If, on the other hand, I'm simply trying to get a bunch of images processed for approval, trying to make them good rather than great, I'll apply a quick sharpen here, knowing that I can reprocess the "hero" shots from the raw file with no sharpening once I know which ones they are.

Luminance Smoothing

The Luminance Smoothing slider lets you control grayscale noise that makes the image appear grainy—it's typically a problem when shooting at high ISO speeds. The default setting is zero, which provides no smoothing; but many cameras benefit from a modest amount—say 5 or so—of luminance smoothing even at slow speeds, so you may want to experiment to find a good default for your camera. At very high settings, the Luminance smoothing slider produces images that look like they've been hit with the Median filter, so always check the entire image at 100% view or above before committing to a setting.

Color Noise Reduction

Color noise manifests itself as random speckles of color rather than gray, and again it's a bigger problem on some cameras than on others. I usually leave this control at its default setting of 25 unless I see a need to increase (or, much more rarely, reduce) it.

The Lens Tab

The controls in the Lens tab let you address two problems that occasionally show up in digital captures, one much more common than the other (see Figure 3-20). The up and down arrow keys move the sliders in increments of 1. Adding Shift moves the sliders in increments of 10.

Figure 3-20 The Lens tab

Chromatic aberration

Chromatic aberration is a phenomenon where the lens fails to focus the red, green, and blue wavelengths of the light to exactly the same spot, causing red and cyan color fringes along high-contrast edges. In severe cases, you may also see some blue and yellow fringing. It typically happens with wide-angle shots, especially with the wide end of zoom lenses. Vignetting, which is much less common, happens when the lens fails to illuminate the entire area of the sensor evenly, and shows up as darkening in the corners of the image.

Some pundits claim that chromatic aberration in digital captures is caused by the microlenses some camera vendors place in front of each element in the array, but I'm skeptical—I've seen it happen on cameras without microlenses, using wide-angle lenses that don't display chromatic aberration when shooting film. I believe it's simply because digital capture is more demanding on lenses—film scatters the incoming light due to grain and to the presence of the multiple layers in the emulsion, so it's somewhat more forgiving than digital sensors. Whatever the reason, it's entirely likely that you'll encounter chromatic aberration in some wide-angle shots.

• Chromatic Aberration R/C. This slider lets you reduce or eliminate red/cyan fringes by adjusting the size of the red channel relative to the green channel. While the red/cyan fringes are usually the most visually obvious, chromatic aberration usually has a blue/yellow component too.
• Chromatic Aberration B/Y. This slider lets you reduce or eliminate blue/yellow fringes by adjusting the size of the blue channel relative to the green channel.

Figure 3-21 shows before-and-after versions of a chromatic aberration correction. As with the controls in the Detail tab, I always zoom the preview to 100% or more when making corrections with the chromatic aberration sliders.

Figure 3-21 Chromatic aberration correction

Vignetting

Vignetting, where the lens fails to illuminate the entire sensor area, darkening the corners, is a less-common problem with digital capture because the sensor area is usually smaller than the film for which the lens was designed. But if you do encounter it, the vignetting sliders can help compensate.

• Vignetting Amount. This slider controls the amount of lightening or darkening (negative amounts darken, positive amounts lighten) applied to the corners of the image.
• Vignetting Midpoint. This slider controls the area to which the Vignetting Amount adjustment gets applied. Smaller values reduce the area, larger ones increase it.

The Calibrate Tab

This set of controls lets you fine-tune the behavior of the built-in camera profiles to tweak for any variations between your camera and the one that was used to build camera Raw's built-in profiles for the camera model (see Figure 3-22). The up and down arrow keys move the sliders in increments of 1. Adding Shift moves the sliders in increments of 10.

Figure 3-22 The Calibrate tab

I find that an effective way to use it is to shoot a 24-patch Macbeth Color Checker and then compare it with a Lab version of the target, converted to your chosen RGB working space. You can download a Lab image of the Color Checker, made from averaged measurements of several physical targets, at www.colorremedies.com/realworldcolor/downloads.html.

If you're shooting under controlled lighting, do a custom white balance in the camera before capturing the target. In all cases, make sure that the target is evenly lit, and avoid having anything significantly brighter than the target's white patch in the scene—using shiny metal clips to hold the target in place is a Bad Idea!

Start by adjusting the controls in the Adjust panel to get approximately the same luminance values for the black and white patches as are in the Lab file, and use the tonal controls to get an approximate visual match to the gray patches in the Lab image. It's better to concentrate on getting a good visual match rather than trying obsessively to match the numbers exactly, but if you want to build a calibration setting for a specific lighting setup, it's worthwhile to look at the numbers as well as the visual match.

If you want to go by the numbers, convert the Lab image of the Color Checker to the RGB space you've chosen in the workflow settings' Space menu, and type the RGB values for each patch on text layers. That way, you can compare the RGB numbers in the Color Checker image with those supplied by Camera Raw's RGB readout—see Figure 3-23.

Figure 3-23 Setup for using the calibrate controls

Don't try to achieve an exact numeric match for every patch—that's a fast route to the funny farm! Instead, try to nail the relative overall hue and saturation relationships, using the numbers as a guide. Two handy shortcuts let you keep the cursor on the image to read the RGB values while you adjust the controls. The Tab key selects the next field. The up and down arrows increase and decrease the values in the selected field by 1, while adding Shift changes the increment to 10.

Tonal adjustments

Before touching the Calibrate controls, use the tonal controls in the Adjust tab to create a reasonable contrast match to the Color Checker image. I suggest the following step-by-step procedure, always comparing the patches in the raw image to those in the Color Checker image.

1. Use the Exposure control to match the white patch.
2. Click the White Balance tool on the second-lightest gray patch (Row 4, Column 2 of the target).
3. Use the Brightness control to match the mid-gray patches (R4C3 and R4C4).
4. Use the Contrast control to fine-tune the darkest patches (R4C5 and R4C6) and the second-to-lightest patch (R4C2). In some cases, you may need to use the Shadows slider to get the darkest patches where you want them.

Often, you'll find that you need to bring the Brightness and Contrast values down to the point where the image looks extremely flat. Don't worry—this is normal, and the goal is simply to get the overall contrast to a point where you can achieve reasonable color matches. Once you've tweaked the color response in the Calibrate tab, you'll find that you have a great deal of freedom to tweak the tonality without affecting hue and saturation. But if you don't match the overall contrast of the target, your color tweaks will be wildly off, and they'll produce unpredictable color shifts as you tweak the tonal values.

The final adjustment you'll want to make before turning your attention to the Calibrate tab is to the Saturation slider. Examine the red, green, and blue patches in the Color Checker (R3C1, R3C2, R3C3, respectively), and note the Red value for the red patch, the Green value for the green patch, and the Blue value for the blue patch; then adjust the Saturation control to get the values in the capture to match the values you just noted in the Color Checker image as closely as possible—there will likely be an element of compromise here, so just get as close as you can. This is the one step where it's easier to go by the numbers than to proceed visually. See Figure 3-24.

Figure 3-24 Adjust tab preparation for the Calibrate adjustments

Calibrate adjustments

The Calibrate tab offers a Shadow Tint control and separate Hue and Saturation controls for Red, Green, and Blue.

• Shadow Tint. This slider controls the green-red balance in the shadows. Negative values add green, positive values add red. Check the darkest patch on the target. If it's significantly non-neutral, use the Shadow Tint control to get the R, G, and B values to match as closely as possible—normally, there shouldn't be more than one level of difference between them.
• Red, Green, and Blue Hue. These sliders work like the Hue sliders in Photoshop's Hue/Saturation command. Negative values move the hue angle counterclockwise, positive values move it clockwise.
• Red, Green, and Blue Saturation. These sliders work like gentler versions of the Saturation slider in Photoshop's Hue/Saturation command. Negative values reduce the saturation, positive values increase it.

The key point to wrap your head around in using the Hue and Saturation adjustments is this: The Red Hue and Red Saturation sliders don't adjust the red value, they adjust the blue and green; the Green Hue and Saturation sliders adjust red and blue; and the Blue Hue and Saturation sliders adjust red and green. That's why you need to adjust the global Saturation control in the Adjust tab first!

Concentrate on the red (R3C1), green (R3C2), and blue (R3C3) patches in the target. Positive adjustments to the Red Hue slider increase green and decrease blue, negative ones decrease green and increase blue. Positive adjustments to the Red Saturation slider decrease green and blue equally, negative ones increase green and blue equally. Adjust the Red Hue and Saturation while checking the red patch, the Green Hue and Saturation while adjusting the green patch, and the Blue Hue and Saturation while adjusting the blue patch. See Figure 3-25.

Figure 3-25 Calibrate adjustments

You'll quickly notice that everything you do here affects everything else! You may have to go through two or three rounds of tweaking the sliders, and possibly revisit the tweaks you made in the Adjust tab. But if you persevere, you'll find that five to ten minutes work can get you a very close visual match.

An exact numeric match is unlikely, but you can get close. The important things to nail are the relative hue and saturation of the red, green, and blue patches—when you get these right, the rest of the color pretty much falls into place. You may want to create separate calibrations for tungsten and for strobe or daylight—many cameras respond significantly differently to tungsten and to daylight (or daylight-like) sources.

Once you've dialed in your camera's response, you can save the Calibrate settings (along with any other settings you'd like to make defaults) as a new Camera Default for that camera, using the Save Camera Default command on the Camera Raw menu.

It may be tempting to use the Calibrate controls as color-correction tools, and within limits you can do so; but if you see a need to do so, it's usually a sign that the calibration for your camera leaves something to be desired. That said, the Calibrate controls offer some interesting creative possibilities that I'll demonstrate later in this chapter.

Figure 3-26 shows images from several cameras before and after applying custom calibration settings. They demonstrate the effectiveness of the feature in dialing in the performance of very different cameras. Here are a few pointers in getting the most from the Calibrate tab.

• In the initial contrast edits, it's unlikely that you'll be able to maintain the tonal separation of the white patch from the second and third gray patches. Use the white patch to set the initial Exposure adjustment, then concentrate on the other gray patches to make the Brightness, Contrast, and Shadows edits.
• When you go to make the Saturation edit in the Adjust tab, you'll typically find that the red value of the red patch is higher and the blue value of the blue patch is lower than the aim points. Set the master Saturation to match the green value on the green patch.
• In the Calibrate tab, I suggest editing the Shadow Tint using the black patch, then the Green Hue and Saturation, followed by Blue Hue and Saturation, leaving Red Hue and Saturation for last.

Figure 3-26 Before and after calibration