In May, we analyzed usability guru Jakob Nielsen’s report on iPad design and concluded that it was a welcome return to form for the web veteran. Nielsen and his company have followed up with another excellent usability report, this time about “transmedia” design. It covers mobile, tablets, TVs and even dips a toe into “extreme screen sizes” (very small or very large screens).

The latest report convincingly argues that although use of mobile devices will dramatically increase, there will still be “much high-value use” on desktop PCs. “One size UI does not fit all screen sizes,” the report somewhat obviously points out. The details though are worth looking at, as it shows how user experiences across devices and screen sizes will increasingly differ.

Nielsen argues at length that PCs are better for a range of activities, but particularly office work. “It’s fairly certain that the highest-value use will stay predominantly on desktop,” he writes, “thus, the percentage split of value between devices will be more favorable to the PC, even if the percentage split of time increasingly turns more toward tablets and phones.”

Regardless of how much value people derive from PCs compared to mobile, the reality is that most companies these days require both a website for PC viewing and one for mobile viewing. Nielsen sensibly advocates a different design for PC and mobile devices.

By mobile, he means both smartphones and tablets. Many companies may want a separate design for each, although that isn’t a focus of this particular report.

Finally, Nielsen touches on 3 emerging areas of usability: TVs, very small screens (such as items with embedded RFID chips) and very large screens (such as smart buildings). According to Nielsen, each will need its own UI.

Most companies won’t need to focus on designing for the 3 emerging screen types. Television is the one most likely to need attention in the near future. Currently, writes Nielsen, “designing for TV is relevant primarily for companies in the entertainment or consumer electronics industries.” However he thinks that if interactive TV usability “improves substantially,” then more companies will need to pay attention to that platform.

Mobile and desktop are the 2 user experiences that most companies need to worry about. The other 3 are dependent on what industry you’re in. Regardless of how many screens targeted, Nielsen recommends that companies factor in these two things: create “separate and distinct UI designs for device categories that are sufficiently different” and retain the feel of a product family across devices.