Observational representationalists are often faced with scenarios in which a seemingly linear translation requires values or colors that reach outside of an available material gamut (value/color range achievable with the materials). In contending with the issue, artists often turn to one of two options: 1. Transpose all values/colors evenly to maintain a “homomorphic” set of value/color relationships (each value evenly shifted to better align with the material gamut) or 2. Truncate the range at the gamut ceiling to maintain a region of perceptibly linear correlation where possible. Let’s look at these options a bit closer so as to better understand why I tend to lean towards one over the other.
First, it should be clear that while we do not see in terms of objective physical measurement—observational representationalists make a great effort to build an effective biological percept surrogate through the recording/communication of those psychophysical qualities experienced during the observation of a subject.
In the top left of this graphic we see a subject (cube) that is represented with a value range that is greater than the range of the available material gamut. To the slight right of the cube is a graphic representation that shows the perceived range of value and a representation of the material gamut range. There is alignment for a significant length, but this alignment ceases where the material gamut ends.
Transposition, or an equal shifting of all of the relationships to accommodate the material gamut, is often not the best answer. While such a carefully planned shift can maintain strong relationships, the overall representation seems far more distant from the aggregate of the subject (not to mention how challenging it would be to maintain this even transposition as the representation develops). The bottom right shows the evenly shifted, or transposed representation.
Truncation with partial edge transposition (middle) seems to generally serve the goals of the observational representationalist far better. As with most of our drawing and painting endeavors, anchors are established early on so as to designate the extremes our visual representation. Analogous values near these anchors are then modestly transposed, decreasing in transposition severity as they reach the green “goldilocks” zone where the psychophysical values and material gamuts can align.
There are indeed other ways that artists do contend with such issues and I would welcome anyone to share their experiences here.