Image Acquisition
With the color camera the value distribution is displayed separately for each
color channel in three lines (red, green and blue).
If an image is overexposed, at least one curve on the histogram is cut off at
the right-hand edge of the display area, where it forms a maximum. Reduce
the exposure time or insert gray density filters into the microscope’s beam
path to reduce the amount of light. It is also possible to reduce the lamp
voltage of the microscope illumination. However, this changes the basic color
of the illumination (color temperature) and requires a new white balance.
If an image is underexposed, the histogram does not reach the right-hand
edge of the display area. As a result optimum use is not made of the camera’s
resolvable gray value range. You should therefore increase the exposure time
or the amount of light in the microscope.
Log
: By clicking on this button it is possible to influence the histogram display.
You can toggle between a linear scaling and a logarithmic display of the
signals represented in the histogram.
The logarithmic display makes it possible to view small amplitudes and high
peaks at the same time in a single overview. Otherwise, because of the
automatic scaling of the display, small signal values are often not visible in the
diagram.
Skip
: This function can be used to influence the automatic scaling of the
histogram. If an image contains an extremely bright glare or extremely dark
features the result will be overexposure or underexposure of the image in
these areas. All of these pixels possess the maximum / minimum numerical
value which can be displayed (e.g. in an 8-bit image 255 for overexposure or
0 for underexposure). Consequently, for the gray value 255 the histogram has
to display an extremely high number of pixels with the same value. As the
scaling of the histogram curves is automatically adjusted to this high value,
smaller values can no longer be resolved in the display.
By using the
Skip
function the maximum values at the upper and lower end
of the histogram are omitted during the scaling of the display.
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M 60-3-0014 e / printed 12.2008
