Image Processing Reference
In-Depth Information
When setting the exposure, you can control the way the highlight
restoration is handled. Therefore you use the symbol with the light bulb.
The first setting (upside-down bulb; default) restores the highlights in the
LCH (Luminosity, Chrominance, Hue) space. This restores the luminosity
while preserving the chrominance and hue. The results are soft natural
details in the highlights (symbolized by the bulb illuminating the object
fully and directly from the top).
The second setting (bulb lying on its side) restores highlights by using
the HSV color space (Hue, Saturation, Value; Value stands for brightness).
If you choose this setting, the value (which corresponds to luminosity) is
taken as an average of the clipped and unclipped values. The results are
sharp details in the highlights (symbolized by a bulb lighting the objects
from the side).
The third setting (scissors) clips the highlights completely and guarantees
that there will be no artifacts when they are restored.
The three options play a role
only when you are working with
negative light values, hence when
you are darkening an image.
By applying the next setting, you can control the way in which the
exposure is applied when you are highlighting an image. Notice, that clicking
this button changes the symbol on it and thereby the setting.
The first setting (the symbol of a colored checkerboard resembles a
camera chip) emulates the linear response of a digital camera sensor.
Though it may be mathematically correct, the result may be contrast that
is too harsh.
The second setting (film) emulates the soft and balanced behavior of
exposed film.
Clicking the auto adjust exposure icon will automatically correct the
exposure settings. Since the correction is done prior to setting the actual
color, the result is not very precise. Other functions in UFRaw also allow
you to (automatically) set options, which will change the settings you
have chosen here.
Clicking the reset exposure to default button resets the exposure to the
program's default values.
UFRaw will “remember” any settings
that you might have defined
while editing an image; it will
automatically apply those settings
to the next image unless you click
the Reset buttons to reset the option
settings to the program default
before you open another image.
You will notice that there is a reset button available for every option so
that you can undo any optional changes and revert back to UFRaw's default
Be aware that the reset white balance button behaves slightly different
than the other reset buttons. Rather than resetting the white balance to
UFRaw's default values, this button resets the white balance to the value
corresponding to the one that was loaded with the image.
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