This color to grayscale conversion uses envelopes formed with the so-called STRESS approach to perform local-difference preserving grayscale generation.
“Presets” are a common feature for several Colors commands. You can find its description in Section 8.1.1, “Colors Common Features”.
Neighborhood taken into account, this is the radius in pixels taken into account when deciding which colors map to which gray values.
Number of samples to do per iteration looking for the range of colors.
Number of iterations, a higher number of iterations provides less noisy results at a computational cost.
When enabled details in shadows are boosted at the expense of noise.
These are common features described in Section 8.1.1, “Colors Common Features”.