MallinCam Universe User Manual page 18

Histogram:
The histogram is a graphical view of the tonal distribution within the image. The horizontal axis
represents the variation in tone, with the darkest pixels to the left (pure black is "0" when the
histogram is not stretched) and the lightest pixels to the right (pure white is "255" in 8-bit mode,
or "4095" in 16-bit mode). The vertical axis and the height of the dark blue column lines
represent the relative number of pixels of a particular tone.
Changing the histogram increases or decreases the visible data in your image. This is called
histogram stretching or dynamic range expansion. Initially, the histogram is set to its Default,
full-range setting ("0" in the left text box below the histogram, and "255" in the right text box).
When you use either the Auto function or the manual method to change the histogram, the values
you set will appear in the text boxes. The minimum value will also be indicated by a vertical red
line on the graph, while the maximum value is indicated by a vertical cyan line. Alter the
histogram by trying one or more of the following methods:
Click the Auto checkbox to let the system determine a histogram stretch. This moves the
minimum and maximum values close to the leftmost and rightmost edges of where the blue
columns first appear in the graph (shown on previous page). The Auto function tries to
maximize the dynamic range displayed onscreen in the preview image, and the image usually
gets noticeably brighter. However, while Auto mode is recommended for use to get an initial
approximation, it is not always the best choice for the final setting of your image.
- OR –
In the manual mode, you can set the minimum and maximum tones to any values in your
image. With the Auto mode unchecked, place your cursor somewhere over the dark blue
histogram columns and right-click the mouse. This sets the maximum and you'll see a cyan
line appear near where you clicked. Notice how the next preview image changes. Now right-
click again, but this time directly over the rightmost blue column of the graph, which is
where you want it. Repeat as required until you get it as close as possible to the right side.
Similarly, left-clicking inside the dark blue columns of the graph sets the minimum and
you'll see a red line appear where you clicked. Try to place it directly over the leftmost blue
column of the graph. Repeat as required until you get it as close as possible to the left.
- OR –
For greater precision, use the text boxes below the display to enter your own minimum and
maximum values and then click OK. The Auto checkbox must be unchecked. The range for
each field is 0 to 255 in 8-bit mode (0 to 4095 in 16-bit mode), with the left field to be set
lower than the right. As with the manual mouse-click method, the goal is generally to set the
red line (minimum) over the leftmost blue column of the graph and the cyan line (maximum)
over the rightmost blue column. Keep trying different values until you get these as close as
possible.
Note that you can always click the Default button and then OK to return to the full (unstretched)
histogram range. The Auto checkbox must be unchecked when you do this.
The histogram can also help you to determine if you are exposing your image properly. If you
only have a few blue columns clustered at the left side of the graph, then you are under-exposing.
Similarly, with the majority of the blue columns towards the right, you are over-exposing. Adjust
the exposure length for a greater spread of columns through the middle of the graph, if possible.
MallinCam Universe - User's Guide v1.05 18