Enblend and Enfuse expect that either

@enumerate
@item
no input image has a color profile or
@item
@cindex color profile
@cindex @acronym{ICC} profile
@cindex profile, @acronym{ICC}
all come with the @emph{same}
@uref{http://@/en.wikipedia.org/@/wiki/@/ICC_profile, @acronym{ICC}}
profile.
@end enumerate

@cindex color appearance model
@cindex @acronym{CIECAM02}
@cindex @acronym{RGB} color cube
@cindex color cube, @acronym{RGB}
@noindent
In case@tie{}1 the applications blend or fuse in the
@acronym{RGB}-cube, whereas in case@tie{}2 the images first are
transformed to @uref{http://@/en.wikipedia.org/@/wiki/@/CIECAM02,
@acronym{CIECAM02}} color space -- respecting the input color profile
-- then they are blended or fused, and finally the data transformed
back to @acronym{RGB} color space.  Moreover, in case@tie{}2, Enblend
and Enfuse assign the input color profile to the output image.

Mixing different @acronym{ICC} profiles or alternating between images
with profiles and without them generates warnings as it generally
leads to unpredictable results.

@cindex @acronym{sRGB} color space
@cindex color space, @acronym{sRGB}
The options@tie{}@option{--ciecam} (@pxref{Extended Options}) and its
opposite @option{--no-ciecam} (@pxref{Extended Options}) overrule the
default profile selection procedure described above.  Use
option@tie{}@option{--ciecam} on a set of input images @emph{without}
color profiles to assign a profile to them and perform the blending or
fusing process in @acronym{CIECAM02} color space.

The default profile is @uref{http://@/en.wikipedia.org/@/wiki/@/SRGB,
@acronym{sRGB}}.  Override this setting with
option@tie{}@option{--fallback-profile} (@pxref{Extended Options}).

On the other hand, suppress the utilization of @acronym{CIECAM02}
blending or fusing of a set of input images @emph{with} color profiles
with option@tie{}@option{--no-ciecam}.  The only reason for the latter
is to shorten the blending- or fusing-time, because transforming to
and back from the @acronym{CIECAM02} color space are computationally
expensive operations.

Option@tie{}@option{--ciecam} as well as @option{--fallback-profile}
have no effect on images with attached color profiles, just as
option@tie{}@option{--no-ciecam} has no effect on images without
profiles.

The impact of blending in @acronym{CIECAM02} color space as opposed to
the @acronym{RGB} cube vary with the contents of the input images.
Generally colors lying close together in @acronym{RGB} space
experience less change when switching the blending spaces.  However,
colors close the border of any color space can see marked changes.

For color geeks: The transformations to @acronym{CIECAM02} color space
and back use

@itemize
@item
@cindex rendering intent, perceptual
@cindex perceptual rendering intent
perceptual rendering intent,

@item
@cindex @acronym{D50} white point
@cindex white point, @acronym{D50}
the @acronym{D50} white point,

@item
500@tie{}lumen surrounding light (``average'' in @acronym{CIECAM02}
parlance), and

@item
assume complete adaption.
@end itemize
