TAILIEUCHUNG - Photoshop CS4 Studio Techniques- P10

Photoshop CS4 Studio Techniques- P10: Staring at a shelf full of Photoshop books at the local bookstore, it seems that there are more special-effect “cookbooks” and technical tomes than anyone would ever care to read. The problem is that none of those “cookbooks” provide enough detail to really let you feel like you understand the program | Chapter 7 Setting Up Images for Final Output Figure Turn off the Preview check box to see the edges of the posterized area. Then turn on the Preview check box and increase the Radius setting until the posterized area appears smooth. Adjusting the image usually causes these gaps. As you adjust the image the bars on the histogram spread out and gaps start to appear. The more extreme the adjustment the wider the gaps. If you see huge gaps in the histogram the posterization probably is noticeable enough that you ll want to fix it it usually shows up in the dark areas of the image . Here s a trick that can minimize the posterization. You have to apply this technique manually to each area that is posterized. Although it might take a bit of time the results will be worthwhile. Don t use this technique on every image -just on those that have extremely noticeable posterization. To begin select the Magic Wand tool set the Tolerance to 0 and click an area that looks posterized. Choose Select Modify Border and use a setting of 2 for slight posterization or 4 for a moderate amount of posterization. Now apply Filter Blur Gaussian Blur until the area looks smooth Figure . Repeat this process on all of the posterized areas until you re satisfied with the results. If you don t have the time or patience to apply the technique described here to eliminate posterization consider choosing Filter Noise Add Noise and using a setting of 3 or 7. This approach can help to reduce posterization but won t be able to help in cases of extreme posterization. If a large number of your images end up with post-scan posterization look into getting a scanner that s capable of delivering 16-bit images to Photoshop. A typical grayscale image contains no more than 256 shades of gray which is technically known as an 8-bit image. That s sufficient for most images but extreme adjustments will cause posterization. One way to avoid posterization is to use a scanner that can produce images containing

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