Manipulating Digital Negatives

Although you still may be working with images scanned from film or print, it's more likely today that much of your Photoshop fodder will come from pictures captured with a digital camera. Digital cameras now outsell film cameras by a hefty margin, and a huge number of the prints that are made are created from digital "negatives."

So, you probably already know that your digital camera may be capable of producing three different types of image files, all of which are well-suited for enhancing within Photoshop CS. You can learn more about them in my book Mastering Digital Photography. In this section, I'll provide a summary of some of the information detailed there.

All newer digital cameras produce, by default, JPEG files, which are the most efficient in terms of use of space. JPEG files can be stored at various quality levels, which depend on the amount of compression used. You can opt for tiny files that sacrifice detail or larger files that preserve most of the information in your original image.

Many cameras can also save in TIFF format, which, although compressed, discards none of the information in the final image file. However, both JPEG and TIFF files are quite different from the original information captured by the camera. They have been processed by the camera's software as the raw data is converted to either JPEG or TIFF format and saved onto your flash memory card or other camera media. The settings you have made in your camera, in terms of white balance, color, sharpening, and so forth, are all applied to the raw image data. You can make some adjustments to the image later using Photoshop CS, but you are always working with an image that has already been processed, sometimes heavily.

The information captured at the moment of exposure can also be stored in a proprietary, native format designed by your camera's manufacturer. These formats differ from camera to camera, but are called Camera RAW, or just RAW for convenience. These "digital negatives" contain all the original information grabbed by your camera's sensor with no compression, sharpening, or other processing.

Each camera vendor's products save images in a proprietary RAW format, which, in some cases (such as Nikon and Canon) are TIFF files with special information embedded. Other cameras produce more esoteric RAW files. All RAW files require special software provided by the camera vendor or a third-party application that can interpret the files. However, because RAW files are generally smaller than TIFF files and include a great deal more information, only a small number of digital cameras (mostly higher-end models) produce TIFF files today. RAW has replaced the TIFF option in most digital cameras.

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