Photoshop Lab Color- P4: LAB has a reputation for enormous power, yet virtually all reference materials that advocate its use illustrate its capabilities with a single class of image. This chapter introduces the basic LAB correction method and explains why it is so extraordinarily effective. if you happen to have a picture of a canyon. | Sharpen the L Blur the AB 91 until it gets there. The usual reason would be that the image is dominated by a single color. In such cases sharpening the two weak channels in CMYK usually works out better than either attacking the L or sharpening all channels in RGB. For example pictures of forests are best sharpened in the black and magenta channels of CMYK if that happens to be possible in your workflow. Pictures like the Johnson Space Center shot we ve just been working on full of different colors are best sharpened overall or in the L. Also if you re planning to take the file into CMYK eventually and are planning to do any kind of major work there you should hold off on the sharpening until it s finished. High Radius Low Amount The L channel often can accept an alternate method of sharpening the Unsharp Mask filter with a very high Radius and a very low Amount. The Radius setting could be anywhere from 7 to 20 pixels as opposed to normal values of around . The Amount is always less than 100 as opposed to much greater values with conventional sharpening. The two methods of sharpening aim at different targets. Conventional sharpening emphasizes edges hiraloam high Radius low Amount sharpening gives shape. Certain noisy images that can t profitably be sharpened conventionally benefit from hiraloam. Some users try to emulate the hiraloam look by creating a duplicate layer setting mode to Overlay and applying Filter Other High Pass. In addition to being more cumbersome it s not as flexible as there is no Threshold setting and it s difficult to evaluate the effect of different Radius values. A full discussion of hiraloam sharpening is beyond this book s scope but it should be noted that it tends to work better in the L than in RGB. If you d like to experiment with the technique yourself I d suggest starting with a portrait shot. Bring it into LAB and with the L channel active apply Filter Sharpen Unsharp Mask at settings of Amount 500 Radius Threshold 0. This .
