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2.3.3 Color Inspection of Individual Image Points and Advanced Frame Options

Information about the color and brightness values of a pixel can be checked in the densitometer in SilverFast 8. A densitometer is a measuring device used to detect the light density of a material. It determines how well a reflective surface or a transparent material absorbs incoming light, that is, how bright or dark they appear. Color values can only be measured indirectly with a densitometer by first using filters to determine the light density of individual color channels, then calculating the color value from that information. This permits the functionality of a colorimeter to be simulated using a densitometer. The densitometer in SilverFast Ai Studio 8 works both as a density meter and as a colorimeter. The preselected color model in the densitometer is RGB, and to the gray scale values of the red, green, and blue color channels and the average black value are displayed correspondingly. For better recognition, the color of the measured point is also shown as a colored area under the columns with the measured values.

To ensure that the user retains full control of the colors in an image, the densitometer shows not only the original values in the left column but also the resulting values in the right column. The latter shows the value the individual color channels and the black value of the measured pixel will have after all image processing steps have been carried out. Fixed measurement points offer an elegant way to continually monitor individual points in the image interactively. SilverFast Ai Studio 8 allows you to set up to four such points in an image; in the SE and SE Plus versions you can set one point. They specify the actual values of the pixel, which is also shown in the densitometer palette in the right column. If you hold the Shift key down, you can use the mouse to set fixed measurement points, move them, or delete them.

SilverFast Ai Studio 8, in contrast with the SilverFast SE Plus and SilverFast SE versions, also offers additional densitometer functions. These are displayed after you click the mortarboard button to enable the Expert mode. In this expanded view, the measured point and its surroundings are shown in a close zoom view, with the X and Y coordinates available underneath. The unit of measurement of the coordinates is set in the uppermost drop-down menu.

The bit depth can be switched between 8 and 16 bits in the second menu. That determines the precision for the numeric specifications of the color and brightness values in the upper part of the densitometer. The radius of the measurement field can be set under that. The values of the measurement point are determined with a radius of 2 pixels by default. That means the value specified is the average of the color value of the pixel itself and the nearest pixels around it. At a radius of 2, this is a 3 x 3 square of pixels, while a radius of 3 specifies a 5 x 5 pixel square whose average will be used as the measured value.

The color and brightness values in the densitometer are displayed in accordance with this setting in the "Mode" drop-down menu. The densitometer in SilverFast Ai Studio 8 supports the color models RGB, CMY, L*a*b*, LCh, HSL, and CMYK.

Once fixed measurement points have been set in the image, the display in the densitometer window can be set to one of those points. In the "Point" drop-down menu, you can switch between the set points and the point under the mouse pointer. The numbers for the points in the menu correspond to the numbers of the points in the image. If you switch to a point, the densitometer shows the numeric values for the colors and brightnesses of the selected fixed measurement point. The pixel zoom, on the other hand, continues to show the point under the mouse pointer.


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