SilverFast Blog

Any CCD or CMOS creates noise no matter whether it is inside a scanner or a camera. Even the most expensive ones show this effect although a lot less than cheaper ones, but they do. Usually noise becomes visible in the shadow areas of an image as random coloured pixels. Now this noise is not only an unintentional effect it also reduces the dynamic range of my image when applying unsharpmasking ! This is because the USM algorithm basically functions as an “edge-detect-and-increase-contrast-around-it” filter. The upside of this filter is the intended sharpening effect and the downside consists of the increased noise in the shadow areas because the edges of the noise pixels will be picked up by the USM as well. Increased noise results in less details in the shadows hence less dynamic range.

SilverFast offers a 2-level interface in nearly all dialogues. This means that the user can access even more controls and sliders when clicking on the little professor icon. In the USM-filter dialogue the user gains access to a lot more controls via the professor like for example the “Sharpen up to” slider. Moving this slider from 100% (black) to 80% means that only those tonal values from 0% (white) to 80% will be sharpened missing out on the shadow areas from 80% – 100% (black) hence those areas where noise is visible. Doing this it will enable the user to apply a USM filter while obtaining the dynamic range of an image or photograph.