Zone of Confidence
The VWG requires a settling on a reference zone of confidence. Mandatory to establish the volume hull of the agreed upon zone of confidence to implement nonlinear transitions.
Zone of Confidence Questions
- The generalized reflectance chromaticities seem like a logical fit here? A direct naive gamut map from camera to target risks completely imbalancing the overall image “intention” by lopsidedly stressing the image as “oversaturated by default.” Reflectance charts seem like a fair trade off here for a region to maintain.
- Zone of confidence plays a role in the luminance targets. An example would be non-Abney magenta shift, as a direct byproduct of gamut clipping. For example, taking typical wider gamuts to sRGB output will lift the luminance to the respective sRGB value, and exacerbating the deep indigos to more-luminous purples.
Hue / Saturation Model
The details of the reference working model needs to be established. While something like JzAzBz has acceptable results for the blue - purple and red - yellow hue skew pinch points, it is also problematic from the EV invariance need. It may be plausible to craft a parametric EV invariant nonlinear xy model, using polar coordinates.
- Establish hull of Zone of Fixation. Direct linear xy paths in the volume up to the hull edges.
- Apply a quadratic bezier curve to certain hue lines that are the most problematic, such as blue purple and red yellow. This would form an infinite plane along Y. A quadratic in xy would meet @carolalynn and @matthias.scharfenber’s to be IDT agnostic.
- Allow a simple tension to control the curvature, and extend from the white point outwards, for tunability during reference design work.
- Interpolate linearly from the radiating nonlinear hue constancy. Remain linear at some polar angle distance after such lines? Establish four lines and sample between?
Hue / Saturation Model Questions
- Are there other options here that maintain EV invariance? Does holding naive Y at a precise value and using xy provide the sole path forward or are there other models?
It is evident that the discussions return to the idea of staged gamut annealing.
- Beyond AP0 to AP0
- AP0 to AP1
- AP1 to ODT
- Given that AP0 represents non-data, should the golden baseline image zone be AP1? IE: Should the image appear optimal at AP1, forming the gold standard for the ODT gamut volume compressions? BT.2020 is currently a reach in display technology, and would form a reasonably future friendly target for a golden image standard point to rally around. Until everyone moves into spectral…
It was mentioned that there was a test bed of imagery. It might be good to have some of the worst offenders in there, and make it available? Where is it currently?
Testbed Imagery Questions
- Where is it currently?
- Some of the more confounding examples in this link would be excellent to trial against. Is it possible to get permission?
Thought I’d throw this out there for discussion. With some of the above currently-fluid facets in place, it would make proofs of principle much easier to execute via Python, etc.