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626 Chapter 20: Managing Scenes and Projects
Opening OpenEXR Files
Any command that opens an image file, such as View
Image File > Specify an EXR fi le. > Click Open. > OpenEXR
Configuration dia log
This version of the OpenEXR Configuration dialog
appears whenever you open an EXR file. It lets
you specify various color transformations to be
applied to the loaded image, designate the internal
storage format to use, and preview the loaded
image with the color transfor m s applied. There
is also a histogram for viewing the brightness
distribution in the image and adjusting the white
and black points interactively.
Inter face
Histogram
To view the histogram, click the Preview button.
The histogr am displays a detailed bar graph of the
distribution of brigh tness throughout the image.
The horizontal axis of the histogram defines the
luminance value, an d the vertical axis indicates the
percentage of the image covered by pixels of that
brightness. Histogram features are:
• T he histogram supports several display modes,
which you can choose by right-clicking the
histogram display window. The menu lets
you choose between li near and loga rithmic
display, automatic or m anual x-axis scaling,
y-axis scale options, and which channel i s
graphed: luminance, red, green, or blue. The
menuentriesX-AxisScaleandY-AxisScale
are simply labels, and are thus unavailable for
choosing.
• The vertical scale slider on the left side of the
histogram lets you adjust the automatically
computed vert ical scale.
• To modify the luminance “window,” set X-Axis
Scale to Manual and adjust the m inimum and
maximum values in the numeric fields below
either end of the graph.
• The background coloration indicates several
pieces of information:
• T he area between the black and wh ite points
is shaded gray.
• The area below 1.0 (low dy namic range)
is a lighter shade of gray than the area
w ith luminance greater than 1.0, the h igh
dynamic range region.
• The background of the region outside the
currently selected blackpoint/whitepoint
region is tinted pink.
• T he vertica l dotted lines indicate integer
spacing (for example, 1...2...3...4). To see
these, the maximum luminance value must
be greater than 1.0.
• You can drag whitepoint/blackpoint markers
in the histogram to place them visually. The
hot-spot is two pixels to either side of the
marker line. White point selection is tested
first, s o if the two lines are right next to each
other,thewhitepointwillbeselected.