Xerox Documate 4790 User Guide

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® DocuMate® 4790
User’s Guide7-143
Gamma
Gamma is the tone curve and starting point for image enhancement. Move the slider left or right to darken or 
lighten the image. As you raise or lower the Gamma value, the values at which Brightness and Contrast affect 
the image are changed. It is recommended that you keep the default gamma value, or adjust this setting before 
adjusting the other options. 
Choosing gamma values
As the gamma value is adjusted lower, the tone curve begins to straighten and the shadows of the image are 
expanded, darkening the shadows without overall darkening the image with gray as seen with lowering the 
brightness level. This way, the highlights and shadows in the image are maintained by saturating the pixels with 
darker levels of the same color rather than adding gray to all colors.
As the gamma value is adjusted higher, the tone curve bends and the highlights of the image are expanded, 
lightening the highlights without overall lightening the image with white as seen with raising the brightness level. 
This way, the highlights and shadows in the image are maintained by saturating the pixels with lighter levels of 
the same color rather than just adding white.
Adjusting the gamma level is based on how you want the image to appear and there is no standard to adhere to.
Color image gamma examples
The examples below show the original image at the default setting of 1.8 gamma level, then 1.0 gamma and 2.6 
gamma. Adjusting the gamma level does not make the image completely black nor completely white.
Technical note:
Most monitors have a gamma setting that is user adjustable. When viewing scanned images on-screen, versus 
printing the image, the gamma setting of the monitor may affect how light or dark the scanned image looks 
when compared to the original. If the scanned image is too different from the original image, or if adjusting the 
scanned gamma level does not modify the image how you want, try adjusting the monitor's gamma level. Refer 
to the monitor's user guide for adjusting the gamma level and see if the manufacturer has any recommended 
settings.
Invert Image
The Invert image option reverses the color of each pixel in the scanned image.  Gamma: 1.0 Gamma: 1.8 Gamma: 2.6 
						

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User’s Guide 7-144 When scanning in black and white, each pixel is reversed from black to white and white to black. When scanning 
in grayscale each pixel is reversed to the opposite level of gray. When scanning in color each pixel is reversed to 
the opposite color in the color wheel.
For example, you might choose this option if you are scanning pages that have been printed from newspaper 
microfilm. Newspaper microfilm reverses black and white so that when viewed on a monitor, the text is white and 
the paper is black.
The following example shows the original grayscale image and the inverted image.
The following example shows the original color image and the inverted image. 
Mirror Image
The Mirror image option flips the image left-to-right. 
						

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Bit Depth Reduction
The Bit depth reduction options are only available when scanning in black and white. Click the drop down menu 
and select an option from the list.
Threshold and Dynamic threshold
Threshold enables you to set what level of light or dark to look for on a page. When scanning in black and white, 
everything on the page is set to either white pixels or black pixels in the final image. If the text on the page is a 
light color, then the text may be gone in the final image as the scanner will change those light colors to white 
pixels. The threshold slider lets you set the level of darkness or lightness of the text on the page. Dynamic 
threshold attempts to evaluate the image and dynamically adjust the threshold level. These options work best 
for documents that contain only text such as business letters, spreadsheets, reports, etc...
•Threshold—move the slider to the left or right to set the level of lightness or darkness for the scanner to 
leverage from. 
For example, if you are scanning a document with gray text, such as hand written pencil notes, move the 
slider to the right. This tells the scanner that the level to look for is light, and gray pixels are converted to 
black pixels instead of white. If the overall tone of the original document is dark, such as a colored 
background that may interfere with detecting black, move the slider left. This tells the scanner that the level 
to look for is dark, only very dark areas such as text are converted to black pixels.
If you are scanning documents that are in good condition, with black text on a white background, the default 
threshold option will properly scan the item. This level only needs to be adjusted if the scanned image does 
not have image clarity similar to the original.
•Sensitivity—move the slider left or right to adjust the sensitivity level for dynamic thresholding. This slider is 
only enabled when Dynamic threshold is selected in the list.
Error diffusion, Bayer, and Halftone pattern
Error diffusion, Bayer, and Halftone patterns are the intentional application of noise (dithering) in the image to 
help alleviate banding when scanning in binary (black and white) mode. For example, if you scan a color photo in 
black and white, the image file will have large blocks of black and white and the image barely recognizable. 
Dithering the image creates a black and white image that is recognizable. 
Below is an example of a color scan, a black and white scan without dithering, and a black and white scan with 
dithering. When the image is scaled down, it may look like a grayscale scan. When the image is at normal size or 
enlarged you will be able to clearly see the dithering pattern, as shown in the close-up image.
Color scanBlack and White scan Bayer dither scan 
						

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User’s Guide 7-146 Bayer dither scan - Close up
Mixed Content Options (Text and Graphics)
The Bit depth reduction list includes automatic separation options for mixed content documents containing both 
text and graphics.  These options enable the scanner to evaluate the image for text and graphics, and then apply 
threshold to the text regions and a dither pattern to the graphics regions. This retains text clarity while providing 
graphic legibility. 
The mixed content options are:
• Threshold – Diffusion
• Threshold – Bayer
• Threshold – Halftone
Fill Margin Holes
Select this option if you are scanning pages with punched holes in the margins. This option will fill these holes 
with the detected background color in the final scan.  The scanner will detect and fill the holes under the 
following conditions:
• The size of the hole can be between approximately 4 mm and 12 mm
• The maximum width of the margin is 25.4 mm from the edge of the paper
• The size of the margin is 24.4 mm 
						

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User’s Guide7-147 • The position of the hole cannot be flush to the edge of the margin area and it cannot overlap the edge of 
the margin area
Color Processing Panel Options
The options in this panel are for setting how the scanner should process colors in specific color modes.
Color Dropout
Color dropout tells the scanner and software to remove a specific color from the image. You can choose either 
Red, Green, or Blue, or define a custom color, to be dropped out of an image. 
To input a custom color using its RGB value, select Custom in this list and then input the values for R, G, and B in 
their appropriate boxes, where R, G, and B are numbers from 0 to 255. 
To l e r a n c e—use the slider to adjust the precision of the color dropout. 
•More precise—this option removes a range of colors closest to the pure color selected or defined in the 
custom fields. For example, pure red has an R/G/B value of 255/0/0. Selecting Red indicates that the scanner 
should look for a range of RGB reds close to pure red and remove them from the image. 
•More approximate—this option removes a wider range of colors based on the pure color selected in the list 
or defined in the custom fields. 
						

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User’s Guide 7-148 This option is only available when scanning in grayscale or black and white. The example below shows the 
original text with a red watermark and the resulting image with the color removed.
Perform Color Correction
Apply color correction to the image so the displayed colors approximate the original item colors. Select this 
option to use the scanner’s default Gamma table which has been calibrated to produce the best quality color 
results for your scanner. When this option is not selected, the resulting scans will be dark and the brightness, 
contrast, and gamma options will require a greater amount of adjustment to affect the overall lightness of the 
image.
Automatic Color Detection Options
Select Automatic in the document source configuration list to enable these options.  When you have selected the 
automatic color mode, you will also need to choose either Gray or Black & White. 
•Ignore document color—select this option to have the scanner ignore the color of the document when 
determining if the scan should be saved as a color image.
•Color percentage—input the percentage of color pixels the scanner should look for to detect and save a 
color image.  The scanner determines color versus black-and-white by comparing the amount of color to the 
amount of black in the image.  The higher the value you set in this field, the more color is needed in the 
original item to detect and save it as a color image. You can set the color percentage level up to 50%. This 
means that only those documents which have more than 50% of the content in color will be saved as a color 
image.
Advanced Panel Options
The options in this panel may also appear in the Main panel, but with additional settings for you to fine-tune the 
feature you've selected. Select the Advanced source configuration mode to show this panel. 
						

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Despeckle
This option removes speckles from the background. Speckles are small spots on an image that the scanner 
interpreted as a valid part of the document. For example, an irregularity in the paper, a small wrinkle, or holes 
where a staple was removed may show up as speckles in the scanned image. The Despeckle option identifies 
these spots and removes them. This option is only available when scanning in black and white. 
Radius—this is the size of the area that is evaluated for stray dots. 
Image Emphasis
Select how much to emphasize image content when scanning printed items. You can use Image emphasis to 
improve the clarity of the scanned images by sharpening the appearance of lines within the image.  The Smooth 
option works best for scanning photos to keep the colors in the pictures blending smoothly together.  The options 
for Low, Medium, or High increase the sharpness of the lines in the scanned image and work best when scanning 
text documents. The Automatic option tells the scanner to attempt to choose the best emphasis level based on 
the items currently being scanned. This option is only available when scanning in Color or Gray.
Here is an example of text at a 4 point font size scanned with the Image emphasis set to None and scanned a 
second time with the Image emphasis set to High. The scanned examples are enlarged to show details.
Moiré Reduction
Moiré patterns are wavy or rippled lines that may appear in the scanned images of newspapers and magazines, 
and sometimes scanned images of photos, line drawings, and color scans of textured paper. Select the Moiré 
reduction option to have the driver attempt to find and remove moiré patterns from the image. Please note that 
when Moiré reduction is enabled the scanner may scan slower as the image is checked for moiré patterns. This 
option is only available when scanning in Color or Gray. Original text:
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz
ABCDEFGHIJKLMNOPQRSTUVWXYZ
abcdefghijklmnopqrstuvwxyz
Scanned with no image emphasis: Scanned with high image emphasis:
Image with moiré patterns Image with moiré patterns 
removed 
						

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User’s Guide 7-150 Moiré radius—you can set the size of the area to be evaluated in the Moiré radius field. Adjusting the radius will 
produce different results for the various types of items that can be scanned. With this feature, you may have to 
test scan a few times, adjusting the Moiré radius as needed, until you obtain the best results for the type of paper 
in your scan job. Note that the higher the number is in the Moiré radius field, the longer it will take the driver to 
evaluate the image.
Smooth Background
Automatically detect the background color of the scanned item, eliminate minor variations, and make it a solid 
color in the image. For example, when scanning a blue page the color will be represented in the final scan with 
varying RGB values representing blue. These varying RGB values occur due to imperfections in the paper being 
scanned. With Smooth background turned on, the pixels representing the page color are changed to an average 
value of the colors detected.
Remove Background
Automatically detect the background color of the scanned item and set it to white in the image.Color scan Color scan with Smooth background
Gray scan Gray scan with Smooth background
Color scan Color scan with Remove background 
						

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Initialize White Level From Document
Automatically detect and adjust the white level using the leading edge of the scanned item. This is a feature that 
uses the scanner for processing and it is available whether or not Visioneer Acuity is installed.  However, please 
note that there will be a black line at the top of each image.  This is where the scanner starts the image capture 
as the reference point for it to detect and set the background as white in the image.
When Visioneer Acuity is installed, we recommend you use Remove background if you want to have the 
background automatically removed without seeing this black line.
White Level
With this option you can set what the scanner should interpret as “white” in the final image, even though the 
page being scanned may have a shaded or off-white background. You may want to adjust this option to have the 
image automatically corrected when you are scanning irregular paper, such as thick or thin paper, that may 
cause the white page in the final image to appear shaded with a pale grey. This option is only available when 
scanning in Color or Gray.
For the best automatic results you can simply select the type of paper you are scanning from the list.  
Alternatively, you can input a number in the Custom value field. The value you set in this field can be from 128 to 
255. If you set the custom value to 128 you are telling the scanner that all pixels that are grey level 128 or higher 
(lighter) should be changed to white in the final image. If you set the custom value to 255, you are telling the 
scanner that only pure white is white and anything lower than 255 should remain unchanged in the final image.
Black Level
With this option you can set what the scanner should interpret as “black” in the final image. If you are scanning 
items that have notes written with a pencil, you may want to raise the black level to have the pencil notes appear 
black in the image.  You can set a value for black from 0 to 127.  If you set this value to 127, you are telling the 
scanner that all pixels that are grey level 127 or lower (darker) should appear as black in the final image. This 
option is only available when scanning in Color or Gray. 
						

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Driver Configuration
Use the Driver configuration section to configure the add-on modules, select interface options, and view the 
scanner hardware properties. When the Advanced configuration mode is selected, a scanner panel option will be 
available for you to change any hardware settings that may be available for your scanner.
Disabled Options in this Section
Some options in the interface may be grayed out and cannot be selected. Grayed out options are either not 
appropriate for the current scanner, the software needed to enable the feature is not installed, or the feature is 
dependent on another setting in the scanner's interface. Hover the mouse cursor over a grayed out feature to see 
information about why the feature is unavailable.
Module Configuration
When image processing modules are installed they will appear in the list on the Configure tab. Use this tab to 
enable the modules you want to use when scanning. 
There are some features in the scanner interface that are disabled until a module is installed that contains those 
options. When the module is installed, the features will enable in the scanner interface for you to use them. 
Reordering the Modules
Select a module in the list and click the up or down arrow to change the order of the module in the list. Changing 
the order of the modules changes the order in which the image processing options are used. For example, if there 
are two modules installed and both modules include an automatic image rotation option, the first module's 
rotate option is used and the rotate setting in the second module is ignored so that the image is not rotated 
twice.