Rgb Histogram - Canon CHDK User Manual

• +1EV -
Increases shadow detail by
• +2EV -
Increases shadow detail by
• Auto DR
Auto DR with Zebra is intended to be used for the direct application of the curves to the shot - and
not for post processing (the feature is just mimic of the Fuji S100 +200, +400 Dynamic Range).
The workflow is:
1. - Activate Zebra display
2. - Activate Auto DR
3. Use the camera EV negative compensation to reduce the Zebra overblown highlights shown
on screen. You can use the (+/-) button on the back of the camera.
4. Take the shot. You will directly get the JPG without post processing. The luminance of the
darker areas will be raised while the highlight is compressed.
During the RAW develop process, you need to set the EV comp. to the value that you used to
reduce the highlight blown out when you took the RAW. Care should be taken with in camera
develop since it is a tricky art there (for White Balance issues in particular).
If the scene does not require you to reduce exposure to avoid blown highlights, the Auto DR
feature does not do anything.
Load Curve Profile
Load your choice of curve profile from the /CHDK/CURVES folder. All curve profile files
except for
SYSCURVES.CVF
See also:-
Histogram parameters
Enables and customizes the Live Histogram feature.
Histogram Anatomy
The horizontal component of a histogram runs from 0 to 255. What is
important to understand is the "0" and "255" are not values...they are
labels representing a color value. When you see a line in the middle of
the histogram (label "127") it's saying "this is how many '127's there
are in the image."
The vertical component of a histogram is the count of pixels at a given level. The bottom is zero and the
top represents the largest count of values for a label. So if you have a 7MP image and every color is
"127", then the top of the histogram represents 7 million pixels.

RGB Histogram

RGB histograms simply count pixels at each level. The RGB histogram of an image of three boxes (red,
green, and blue) where every color has a value of 127 would be a single line in the middle of the
histogram (at label "127".)
Luminance (Y) Histogram
Luminance histograms attempt to factor in the perceived brightness of colors. A luminance histogram of
an image of three boxes (red, green, and blue) where every color has a value of 127 will show three lines
at labels "38" (red- x 0.3), "75" (green x 0.59), and "14" (blue x .11).
(auto dynamic range):
should be in this folder.
Curves notes on page 54.
< Main Menu
1EV
step.
2EV steps.
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