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So why trade grain for softening of the image, surely we can do the same in Photoshop? Not quite! The screenshot below demonstrates that there is more to the SilverFast Descreen filter than simply removing the moiré effect and softening. I usually engage the "use Unsharp Masking" filter to help bring back some sharpness to the image. In fact I now find that with some images very fine detail returns - notice the appearance of a hair strand on the bottom right of the "Descreen" preview window.



Descreen and Unsharp Mask Filter


So what are the sliders doing? With SilverFast USM takes place on-the-fly in Lab mode hence the % values and references to grey in the user manual.

  • Intensity will determine the amount of sharpening that takes place. Typically we should set low values between 15 and 40%. Occasionally values above 50% can be used, but these are rare.

  • Threshold determines where the sharpening will take place ( i.e. contrast between two adjacent pixels). Values between 2 and 6 are normal. If high Intensity values are used it will be necessary to further increase the Threshold.

  • "Sharpen down to" is a bit more complex to explain but basically determines how far into the shadows the image will be sharpened. Go too far down and shadow noise will become more pronounced than we would normally desire. It's probably better to experiment with different values.

  • I tend to leave "Light and Dark Contour" at the default values. Modifying either will tend to cause black or white specks to become less or more pronounced. Increase "Light contour" value and white specs will jump off the screen at you, likewise increasing the "Dark contour" value will cause any dark specs to become even blacker. Experimentation is the name of the game with these two sliders. If the image has lots of speckles it is certainly worth adjusting one or both sliders.

  • Engage the "Highlights soft" option means that the sharpening effects will not be applied to highlights.

Each of the above adjustment sliders works in "real-time" so you can easily see the effect of a change in the high-resolution scan window. This window can be scaled up to 8x magnification, but I rarely find is useful above 2x magnification. Hopefully, through some experimentation you to will get less grainy scans than appears to be the case at present.


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