Real World Camera Raw with Adobe Photoshop CS- P4: If you're reading this book because you want to be told that digital really is better than film, look elsewhere. Those discussions tend to generate a lot more heat thanlight, andifyouaren't at least contemplatingshootingdigital for some or all of your work, this book isn't relevant. | 72 Real World Camera Raw with Adobe Photoshop CS The High-Bit Advantage Any camera that shoots raw captures at least 10 bits per pixel offering a possible 1 024 tonal values while most capture 12 bits for4 096 levels and afew capture 14 bits for 16 384 possible tonal values. An 8-bitlchannel image allows only 256 possible tonal values in each channel so when you convert a raw image to an 8-bit channel file you re throwing away a great deal of potentially useful data. The downsides of 16-bitlchan- nel images are that they take up twice as much storage space on disk and in RAM as 8-bit channel ones and an ever-shrinkinglist of Photoshop features don t work in 16-bitlchannel mode. The advantage is that they offer massively more editingheadroom. If you re preparing images for theWeb or you need to use a Pho-featuresuch as mode by means go ahead and process the raw images to B-IÚÍ chan nel files. In just about every other scenario I recommend processing to a 16-bit channel file. Even if you think the image will require little or no editing in Photoshop it s likely that at some point the image will have to undergo a color space conversion for output and making that conversion on a bit channel image can oftenavoid problems such as banding in skies or posterization in shadows that suddenly appear after an channel conversion. Evaluating Images Before starting to edit a raw image it s always a good idea to do a quick evaluation. Is the image over- or underexposed Does the subject matter fall within the camera s dynamic range or do you have to sacrifice highlights or shadows Camera Raw offers three features that help you evaluate the raw image and answer these questions. The histogram lets you judge overall exposure and detect any clipping to black white or a fully saturated primary. The image preview shows you exactly how the converted image will appear in Photoshop and the clipping display available when you adjust the Exposure and Shadows sliders lets you see exactly which
