Apple released a software update Thursday to let its Aperture 2, iPhoto '08, and iPhoto '09 photo-editing software handle raw images from three newer SLRs, Canon's Rebel T1i, Nikon's D5000, and Olympus' E-30.
Higher-end cameras offer raw image formats that provide more flexibility and quality than JPEG, but the raw file formats are proprietary, vary from one camera model to another, and require companies such as Apple and Adobe Systems to release a constant stream of updates. Microsoft relies on camera manufacturers to supply software for Windows that can interpret the raw data, which is taken directly from camera image sensors without in-camera processing.
Camera makers typically supply their own software for handling raw images, but many people prefer their own photo software.
Further detail on Apple's support is available on Apple's raw camera support page.