Adjusting White Balance

In Chapter 5, you saw how you can use the White Balance adjustmentthe Temperature and Tint slidersto alter the color in your image. This adjustment also works on raw files, but Aperture performs its adjustments in a very different way when working with raw data.

On nonraw imagesJPEG, Photoshop, TIFF, and other filesthe Temperature and Tint sliders make changes by redistributing the tones in your image. As you saw in the last chapter, this kind of redistribution can result in data loss that produces visible artifacts.

With a raw file, the Temperature and Tint sliders don't redistribute any tones. Instead, they change the settings for the white balance adjustment that is applied during the raw conversion. Remember: Aperture is performing its raw conversion on the fly, so you're free to change your raw conversion parameters (such as white balance) at any time.

Aperture reads the white balance setting that your camera stores in the image's EXIF information at the time of shooting. If the camera was set for an incorrect white balance, or if its automatic white balance mechanism chose a bad white balance, then your image's initial white balance may be off. This is a fairly harmless problem, as you can easily correct the bad white balance with no loss of image quality.

If your raw image needs any color adjustment, it's best to try to perform as much of this adjustment as you can using the White Balance controls, as these adjustments don't diminish your editing latitude.

When working on a raw file, you'll find that the Temperature and Tint sliders yield slightly different results than they do when used on a nonraw file. You'll sometimes find that you can push and pull your colors to a greater degree (Figure 6.10).

Figure 6.10. Both of these images have had the same white balance adjustment. As you can see, the image on the left, which was a raw file, yields a slightly different result than the image on the right, which was a TIFF file.