Inside Camera Raw

If you have a midrange or pro digital camera, you can probably produce images in the raw format. A raw file is a record of the data a camera’s sensor captures. Shooting raw beats shooting in JPEG format for several reasons, but to benefit from raw’s strengths, you have to edit images using the Adobe Photoshop CS Camera Raw plug-in (free with Photoshop CS). Here’s how.

Balancing Act

Shooting JPEG is like shooting transparency film: you have to get everything perfect in the camera because you can’t do much to reshape contrast and color balance once you’ve captured the image. Raw is superior to JPEG because shooting raw is more like shooting negative film: although you have to process the image before you can see it, you have latitude in how you shape the overall tone and color balance. For example, the Camera Raw plug-in excels at correcting an image’s white balance.

In Camera Raw, the Temperature and Tint sliders (in the Adjust tab) and the eyedropper tool (in the Tool palette) are white-balance tools that let you neutralize any color cast in the lighting, but they’re also interesting as creative tools. The first three screenshots illustrate a range of effects.

You can set an accurate white balance quickly using the eyedropper tool—just click on a near-white or light-gray pixel. (If you get a beep when you click, you’re clicking on a pixel that’s too bright.)

For interesting warming and cooling effects, use the eyedropper and click on darker, near-neutral pixels. For more-precise creative adjustments, use the Temperature and Tint sliders.

The Temperature slider indicates, in kelvins, the color of the light for which Camera Raw is trying to compensate. Moving the slider toward higher color temperatures (bluer light) results in a warmer, yellower image, while moving toward lower color temperatures (yellower light) results in a colder, bluer image. You can think of the Temperature slider as a blue-to-yellow control.

The Tint slider controls the axis that runs perpendicular to color temperature, so it’s essentially a green-magenta control—negative values add green, positive ones add magenta.

As with all the slider controls in Camera Raw, you can adjust Temperature and Tint by moving the sliders with the cursor, but for more precision, use the up- and down-arrow keys. To move the slider a single increment, press the arrow key once; add the shift key to move the slider in increments of ten. Press tab and shift-tab to toggle through the number fields.

Recovering Data

The next two controls in the Adjust tab are Exposure and Shadows. Camera Raw’s Exposure slider is a white-point tool with negative and positive ranges. At positive values, it works like the white input slider in Photoshop’s Levels feature. And its increments are fractions of an f-stop, so adjusting the Exposure slider is like increasing the exposure on the camera using the shutter and aperture controls.

At negative values, the Exposure setting triggers Camera Raw’s extended highlight recovery logic. While most raw converters give up as soon as you clip channels, Camera Raw attempts to reconstruct highlight detail even if it’s present in only a single channel. Now’s the time to bring back that detail—if you don’t recover it in Camera Raw, there won’t be any detail left to recover when the converted image lands in Photoshop.

Like Photoshop’s Levels sliders, Camera Raw’s Exposure and Shadows controls offer a clipping display when you hold down the option key while moving the slider. (Shadows works like the black input slider in Levels.) You see exactly what the software is clipping. Depending on the camera and the white balance, you may be able to recover as much as a stop of highlight data (Seemiddle set of screenshots for examples).

Controlling Tone

Exposure, Shadows, and the remaining tonal controls, Brightness and Contrast, work together to define a five-point tone curve. Exposure sets the white point, Shadows sets the black point, Brightness is a midtone adjustment like the gray slider in Photoshop’s Levels, and Contrast adds two points around the midpoint set by Brightness. The histogram updates in real time as you move the controls.

To make the best use of a raw image’s available bits, use these controls to shape the image’s overall tone and contrast. If you instead bring the image into Photoshop for correction, you’ll lose a great deal of tonal information in the conversion from linear gamma to a gamma-corrected Photoshop working space, making your job more difficult or even impossible (See the last two screenshots for a demonstration).

Tip: Applying Settings to Multiple Images

You can quickly apply the same settings to multiple similar images. First, edit one image in Camera Raw. Then, in the File Browser, select the other images to which you want to apply these settings, and choose Apply Camera Raw Settings from the File Browser’s Automate menu. In the resulting dialog box, choose Previous Conversion from the Settings menu and then click on Update. Photoshop writes the settings to each image’s metadata and uses them the next time you open the images. To bypass the Camera Raw dialog box and open the edited images directly in Photoshop, shift-double-click on them in the File Browser.

Tip: Saving Settings to Metadata

After you edit an image in Camera Raw, you can click on OK and open the image in Photoshop for further editing. But if you hold down the option key, the OK button changes to Update. Click on this button, and you’ll write all the settings you made in Camera Raw to the image’s metadata.

[ Bruce Fraser in a cofounder of Pixel Genius, a collaboraton of industry experts dedicated to creating leading-edge products and services for the photographic and imaging industries. Click here for an excerpt from his book Real World Camera Raw with Adobe Photoshop CD (Peachpit Press, 2004). ]

These three shots demonstrate the power of Camera Raw’s white-balance tools. On the top, you see the raw image at Camera Default settings. In the middle image, I increased the Temperature setting and adjusted the Tint control for a very warm result. On the bottom image, I lowered the temperature for an image with a very cold but still natural appearance.In Camera Raw, you can resurrect fine detail that you’d otherwise lose. In the first image of this sequence, the clouds are blown out. To show the blown-out areas in the middle image, I held down the option key while moving the Exposure slider. To produce the third image, I reduced the Exposure value by –0.75 stop, which restored detail to the clouds.Here’s the Australian outback from above. The image at camera default settings (top) is flat and muddy, and the histogram data is clumped in a very narrow tonal range. To produce the image on the bottom, I made extreme Exposure and Shadows corrections that spread the data across a wider tonal range; then I increased Brightness slightly and Contrast a lot to make the most of the available detail. Lastly, I gave it a white-balance tweak.
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