At the moment, one of the binarization commands (-binary floyd) does not have a detail parameter (more precisely, the parameter is set by default to about 50-60%).
The Floyd Steinberg binarization method allows you to use the detail parameter to get a better black-and-white image (photo).
Please consider adding a detail parameter to this command (as is done in many programs and plug-ins, for example: Ximagic GrayDither). This parameter will only enrich (improve) the program nconvert.
