Normalized to what? For me normalization or weighting is equivalent. Putting it this way there could be different normalization factors. Examples: 1. Averag

Normalized to what? For me normalization or weighting is equivalent. Putting it this way there could be different normalization factors. Examples: 1. Average value over all phones 2. Standard deviation of the value over all phones 3. Minimal noticeable difference in the given property (it's quite vague though, it's basically custom weighting factors) I don't think that there is an obvious best, but I don't think it's needed and all gives sensible results. A more sophisticated distance wouldn't be Euclidean. If you look at x-resolutions and y-resolutions independently you won't catch exotic aspect ratios which should be weighted more compared to a standard aspect ratio phone.