One of the last bastions for screen printing is the ability to print white ink on dark substrates with high opacity, something that has been said couldn't be done successfully with digital printing. But with improvements in both ink and print technology printing, digital white has improved over time, and can now offer very high opacity as well.
But the question is, how you measure ink opacity in the first place? What is high enough opacity, expressed as a number, to be considered fully opaque, meaning that there is no show through of the substrate, e.g. a black substrate? If you ask a manufacturer of digital printing devices you are not likely to receive a clear answer, simply because, until recently, there hasn't been any standardised, recognised way to measure the opacity of printed ink. Digital Dots, working with and for the international standardisation organisation ISO, is trying out a way to measure this in a consistent and predictable way, so you can put a number in a technical specification for the actual “hiding power of white ink”.