One person's artifacts are another person's improvements to their image. It all boils down to this and everyone thinks they are right and stop before visible artifacting. Let's put it this way, I know one Darbee licensee who thinks HD 20 is the limit for serious viewing by him For me its about 35, I guess I either see the artifacts he sees at 35 but count them as image improvements or I don't see them or am insensitive to them. Dr. Darbee thinks some of my posts are insensitive to Darbeevision. So, I wouldn't quarrel with anyone who says 45, 40, 35, 30, 25 or 20 is the acceptable max. Though obviously the higher you go say away from 40, the stranger I would look at you. Once someone tells me 70 at HD makes their image look best, I will ask what kind of sunglasses they are wearing when viewing.
Remember Darbeevision requires a default of 40 in order that people see the improvement brought without a substantial level to most of artifacting. I am sure Darbeevision expects that critical viewers wil turn the level down to a point where they don't see artifacting. For some this will be 35, for most critical viewers around 30, and for the hypersensitive around 20. But if you want to triple stack Darbets all set to full pop 120, go for it. Pass me those sunglasses, the one way mirror silver ones please, so that no one can see I have closed my eyes.