Adobe Photoshop Image Restoration Tutorials
Basics / Unsharp Mask pt. 2
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Subtitles of the Movie (Adobe Photoshop Image Restoration / Basics / Unsharp Mask pt. 2)
Let me show you another aspect to sharpening that you have to keep in mind, and you are going to encounter this more often than you might think. Inevitably when you are sharpening from slide scans, you are going to encounter the issue of grain. Of course the goal is to increase its sharpness without boosting grain and there are ways to achieve that result, and you have to be aware of how to make your adjustments in the unsharp mask in order to do that. Now in this particular image the only thing we are interested in sharpening is the model, we do not want to sharpen anything else. We are going to leave these clouds very soft and certainly we do not want to increase the presence of grain in this photograph. So how do we do that? Let me demonstrate to you the good and the bad in this process, so we are going to go up to the unsharp mask, and the setting that you see there is too much, and what we have here is a situation where we are sharpening really too much and we are increasing the grain as a result and the reason that is happening is because we really should boost this back to a hundred to get it right for the model but we do not want to increase the sharpening on the grain. And the reason the grain is being sharpened is because we have threshold set at zero, meaning every single pixel is being examined for its brightness or darkness and is being reacted upon by the sharpening process, and what we need to do is we have to increase the threshold, meaning that we increase the brightness level at which the sharpening process begins. So we increase the brightness level that the unsharp mask is going to look for when it begins to apply these effects. Adjoining pixels with the same color, or the same color density, are not going to be affected. This is going to be affected because it has a lot of contrast. Okay, we have a lot of different things going on at the pixel level in the model than we do in the background, So when we raise the threshold, we more or less disconnect the background, the contiguous tonal information is going to be rejected, and we are going to concentrate just on the model here. So we are going to hit OK and then let's go back and take a look at the before and after. This is before and this is after. You might not be able to see that too well, but the model is sharpened just enough, you see the ring, you can see the neck, even the freckles on her chest there are even starting to come out, but what we do not see, now take a look at the background when I do the before and after, you see absolutely no increase in the amount of grain that comes out of that because we have adjusted the threshold up to about five or six level on our sharpening process. So if you want to segregate grain in the background, on the solid, you will see this in skies all of the time, you want to segregate the sky from your original subject, whatever that may be, just increase the threshold and that will more or less detach the background from your main subject and it will really, really look good. You cannot totally one hundred percent eliminate it but you can get about ninety percent eliminated. And that is how to use the threshold adjustment to segregate your background.
Tutorial Information
| Course: | Adobe Photoshop Image Restoration |
| Author: | Phil Hawkins |
| SKU: | 33473 |
| ISBN: | 1932072705 |
| Release Date: | 2004-01-27 |
| Duration: | 4.5 hrs / 77 lessons |
| Captions: | No |
| Compatibility: |
Vista/XP/2000, OS X, Linux QuickTime 7, Flash 8 |
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