Real World Camera Raw with Adobe Photoshop CS- P4

Real World Camera Raw with Adobe Photoshop CS- P4: If youre reading this book because you want to be told that digital really isbetter than film, look elsewhere. Those discussions tend to generate a lotmore heat thanlight, andifyouarent at least contemplatingshootingdigitalfor some or all of your work, this book isnt relevant.
Nội dung trích xuất từ tài liệu:
Real World Camera Raw with Adobe Photoshop CS- P472 Real World Camera Raw with Adobe Photoshop CS The High-Bit Advantage Any camera that shoots raw cap- nel images are that they take up nel files. In just about evely other tures at least 10 bits per pixel, twice as much storage space (on scenario, I recommend process- offering a possible 1,024 tonal diskandinRAM)as8-bitlchannel ing to a 16-bitlchannel file. Even values,while most capture 12 bits ones, and an ever-shrinkinglist of if you think the image will require for 4,096 levels, and afew capture Photoshop features dont work in little or no editing in Photoshop, 14 bits, for 16,384 possible tonal 16-bitlchannel mode. The advan- its likely that at some point the values. An 8-bitlchannel image tage is that they offer massively image will have to undergo a color allows only 256 possible tonal more editing headroom. space conversion for output, and values in each channel, so when If youre preparing images for making that conversion on a 16- you convert a raw image to an 8- theweb or you need to use a Pho- bitlchannelimagecan oftenavoid bitlchannel file, youre throwing toshop feature such as Liquifythat problems such as banding in skies away a great deal of potentially onlyworb in8-bitlchannelmode, or posterization in shadows that useful data. by all means go ahead and pro- suddenly appear after an &bit/I The downsides of 16-bitlchan- cess the raw images to &bit chan- channel conversion. Evaluating Images Before starting to edit a raw image, its always a good idea to do a quick evaluation. Is the image over- or underexposed? Does the subject matter fall within the cameras dynamic range, or do you have to sacrifice high- lights or shadows? Camera Raw offers three features that help you evaluate the raw image and answer these questions. r The histogram lets you judge overall exposure and detect any clipping to black, white, or a fully saturated primary. b 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 pixels, if any,are being clipped. r The RGB readout lets you sample the RGB values from specific spots in the image. If an image is too dark or too light, you need to decide whether to fix it by adjusting Exposure or Brightness. If its too flat, you need to decide whether to increase the Contrast value or add snap to the shadows with the Shadows control. For decisions l i e these, Camera Raws histogram is a useful guide. Chapter S; Using O m e n Raw 73When to ResampleA good deal of controversy sur- With the exception of images possible before upsampling, he-rounds the question of whether captured on non-square-pixel cause the work goes faster on ato upsample in Camera Raw or cameras, the differences between smallerfilethanonalargerone. Butpost-conversionin Photoshop. B e upsampling in Camera Raw and others whose judgment I respectvery wary of absolute answers-- upsampling in Photoshop using prefer to upsample in Camera Raw.in most cases, the differences Bicubic Sharper are quite subtle Ultimately, its a question youllare quite subtle and very likely (though I prefer to use Bicubic have to answer for yourself. Y u ocamera-dependent. (And its also Smoother for upsampling). I you f may even find that some typesquite likely theyre photographer- factor in the other variables, and in of imagery respond better to onedependent, too!) That said, Ill particular the huge variable of how method, whileothersrespond bet-give half an absolute answer: if and when you sharpen the image, ter to another. Ifyoure disinclinedyou need a smaller-than-native the question of when to resample to devote a lot of time to testing,file, its a no-brainer to choose becomes even more complex I another entirely rational strategythe size closest to your needs in personally prefer to convert raw is to punt on the whole questionCamera Raw. The controversy re- images at the cameras native res- and simply do whatever is mostally revolves around upsizing. olution and do as much work as convenient in your workflow The histogram. Camera Raws histogram is simply a bar chart that shows the relative populations of pixels at different levels. The colors in the his- togram show whats going on in each channel. White in the histogram means that this level has pixels from all three channels. Red, green, and blue mean that this level has pixels from these individual channels. Cyan means that this level has pixels from the green and blue channels, magenta means this level has pixels from the red and ...