April 13, 2011, 11:47 a.m.
posted by lordnikon
When you’re ready to open a Camera Raw image, double-click the image in the File Browser or choose File>Open and use the Open dialog box. The Camera Raw file format extension is .crw.
Whichever way you decide to open the image, the image automatically opens in the Camera Raw dialog box, as shown in Figure.
The Camera Raw dialog box has a lot of options to select from, but you don’t need to reset them every time you open a raw image. The dialog box has what is called sticky settings — it saves the settings that you used last and opens with those settings selected. After tweaking settings for your camera, you can save the settings and apply them to other raw images.
The rest of this section walks you through the many features and settings available in the Camera Raw dialog box. You can use as many or as few of these settings as you need to get the results you want. If you need a specific setting, just skip to the topic that covers it.
Before you do anything, take a look around the dialog box. Notice that the camera type, filename, and camera settings such as F-stop, exposure time, and lens diameter are listed in the Title bar of the dialog box (see Figure).
The image itself is viewed in a large Preview pane. The Preview pane is dynamic, so every time you make a setting change, the preview updates to let you see what you’ve done.
Also, notice that three tools are at the upper left as shown in Figure: the Zoom, Hand, and Eyedropper tools. As you may have guessed, the
Zoom tool is for magnifying the image and the Hand tool is for moving the image around in the Preview pane. The Eyedropper tool (actually called the White Balance tool in this dialog box) is for setting the options that compensate for various lighting conditions. I discuss its use later in the section “Setting adjustment options.”
The lower-left area of the dialog box contains four drop-down lists that you can use to set color space, resolution, and size. I discuss these drop-down lists in the section “Setting resolution and color space.”
Below the OK and Cancel buttons at the upper-right area of the dialog box are two radio buttons: Basic and Advanced. When you select the Basic radio button, only the Adjust and Detail tabs show in the Settings area. If you select the Advanced radio button, you have access to two more tabbed panels of settings, Lens and Calibrate.
Underneath the Basic and Advanced radio buttons is a histogram, shown in Figure. This histogram shows a combined RGB histogram in white and separate red, green, and blue histograms (one for each color channel). The histogram shows the range of color values in the image.
At the bottom left of the Camera Raw dialog box are four drop-down lists (see Figure). You can set resolution, image size, bit-depth, and the color space. (Bit-depth is the amount of color information in a pixel.) Here’s a description of each option and possible settings.
The Space drop-down list sets the color space. The color space is the range of the color spectrum (also called gamut) in which a device, such as a monitor or digital camera, works. (For more about color spaces and color management systems, take a look at Technique 4.)
You can choose from four options in the Space drop-down list:
Adobe RGB (1998): This color space offers the widest range of colors. Adobe RGB is a good choice for high-quality digital photographs. I usually select this color space.
ColorMatch RGB: Many publishers and commercial printers use this color space. If you are creating photos for offset printing, check with your printer to see whether this color space is the one to use.
ProPhoto RGB: Kodak created this color space for its high-end professional digital cameras. ProPhoto RGB offers a wider range of colors than the other color spaces, but should only be used with Kodak cameras.
sRGB IEC61966-1: Also called sRGB for short (for standard RGB), this color space offers a smaller range of colors and is a good choice for Web graphics.
The Depth drop-down list offers two bit-depth options: 8 Bits/Channel and 16 Bits/Channel. The bit-depth is the amount of color information in a pixel, per channel. The more bit-depth that an image has, the more colors are available. So, the higher the bit-depth, the more accurate the color representation is on-screen and the printed page.
Some typical bit-depth values are 1-bit, 8-bit, and 16-bit. For example, a 1-bit pixel has two possible color values, black and white. An 8-bit pixel has 256 possible color values, and a 16-bit pixel has 65,536 possible color values.
Because Photoshop cs now has the ability to work with 16-bit color images (Photoshop 7 does not), it’s up to you to choose the bit-depth you want to use. The only word of caution is that when you select a greater bit-depth, invariably file size goes up.
The Size drop-down list gives you some image size options in pixels. The image size selected by default in the drop-down list is the size at which your camera captured the image. You can scale up or down depending upon your needs.
Scaling up can have some consequences. Because a larger image needs more pixels, Photoshop adds those pixels to the image, coloring them by selecting color from surrounding pixels. The resulting image can look fuzzy, not clear and sharp like the original.
The Resolution text box and drop-down list let you set how many pixels per inch (ppi) (or pixels per centimeter) your image has. A higher resolution makes for a crisper-looking printed page. Typically, a better digital camera captures Camera Raw images at 240 ppi or greater. (By comparison, the same camera saves the image at 180 ppi when the image is saved as a JPEG.) A good setting for Web graphics and images is 96 ppi.
The Adjust tab panel at the right of the dialog box lets you set the White Balance, Exposure, Shadows, Brightness, Contrast, and Saturation by using slider bars (see Figure).
White Balance describes the lighting conditions in a photograph and how the eye perceives them.
The White Balance area contains two slider bars: Temperature and Tint. Temperature (actually expressed in Kelvin) attempts to reproduce light’s actual color. At lower Temperature settings, a photo appears more cyan; at higher Temperature settings, a photo appears more yellow. The Tint slider bar adjusts the light quality. Lower Tint settings are bluish, while higher Tint settings are redder.
Another feature is the White Balance drop-down list with preset lighting configurations that attempt to re-create different types of light, such as daylight, fluorescent lighting, and flash. Figure shows the available options on the White Balance drop-down list.
Exposure and shadows
The Exposure slider controls highlights, while the Shadows slider controls the shadows (of course!).
When the Exposure slider is dragged left, fewer highlights appear in the photo. Drag the Exposure slider to the right and more highlights appear.
To decrease the amount of shadows, drag the Shadow slider to the left. Drag to the right to increase shadows.
Hold down the Alt/Option key while using either of these slider bars to see a threshold view of the image. This threshold view is handy for finding the lightest and darkest areas of an image, and determining whether any shadows or highlights are getting lost (or clipped).
Brightness, contrast, and saturation
The Brightness, Contrast, and Saturation sliders are pretty self-explanatory; they do what they say. If you need more brightness, contrast, or saturation correction after opening the image in Photoshop, you can use the commands on the Image>Adjustments menu.
The Detail tab panel offers three slider bars: Sharpness, Luminance Smoothing, and Color Noise Reduction, as shown in Figure.
The Sharpness settings in the Camera Raw interface work pretty well. Usually, I do 10% of the sharpening here and the rest in Photoshop using the powerful Unsharp Mask. (Take a look at Technique 37 for tips on using the Unsharp Mask.)
The Luminance Smoothing and the Color Noise Reduction controls remove noise from your photos. When you use these sliders, the Camera Raw interface tries to keep as much sharpness on the edges as possible, but if you go too far, the photo can become a bit fuzzy. Use these settings with a light touch.
You can view the Lens tab panel (shown in Figure) only if you first select the Advanced radio button. The Lens tab panel is used to correct lens conditions that create problems with color focus.
Fixing chromatic aberrations
The Chromatic Aberration R/C slider (R/C stands for Red/Cyan) and Chromatic Aberration B/Y slider (B/Y stands for Blue/Yellow) corrects color problems at the edges of a digital photograph. Sometimes the colors at the edges of a photograph don’t line up, causing what is called fringing. This fringing can create a colored halo effect that is very subtle. To see whether your photo has fringing, you need to zoom in on one of the edges of your photo at the highest magnification, 400%. Slide the Chromatic Aberration sliders back and forth to test how this fringing looks. Return the sliders to a position where you don’t see any color halos.
Removing shadowed vignettes
Both the Vignetting Amount and Vignetting Midpoint sliders correct another lens defect where the corners of the photograph are darker than the center (see Figure).
Figure: Shadowy vignettes at a photo’s edges (top) is a problem created by the lens that Photoshop can correct (bottom).
The Vignetting Amount slider corrects the brightness at the corners of the photo. Moving the slider to the left darkens the corners, while moving the slider to the right brightens the corners.
The Vignetting Midpoint slider adjusts how the brightness moves from the center of the photo to the edges. When you move this slider to the left, the photo appears brighter in the center and darker at the edges. As you move the slider right, the brightness spreads to the photo’s edges.
You can see the Calibrate tab panel only if the Advanced radio button is selected. This tab panel, shown in Figure, sets color and tone by adjusting the color cast in shadowed areas and using the red, green, and blue channels.
Adjusting the color tone of shadows
The Shadow Tint slider works with the White Balance value set on the Adjust tab panel. After a white balance is set, a tinted colorcast can still remain in the shadowed portions of a photo. Move the slider left to increase the greenish cast of shadows; move the slider right to make the shadows redder. If you hold down the Alt/Option key while moving the slider, a threshold view of the shadows in the image indicates whether some shadowed areas are getting lost.
Calibrating the color channels
The Red Hue/Saturation, Green Hue/Saturation, and Blue Hue/Saturation sliders adjust the actual colors in the image. Use these sliders to adjust skin tones or any other image colors until they appear right to your eye.
Don’t forget that you have the power of Photoshop at your fingertips after opening the image. You don’t need to do all your adjustments using the Camera Raw interface. If a color cast doesn’t look right after you open the image in Photoshop, use the commands on the Image>Adjustments menu to help out.