I wanted to post these two images because they show quite nicely the details of two shirts from the period, something you don't often see in Seventeenth Century portraits. Both paintings are attributed to Thomas de Critz the Flemish artist, sometime between 1648 and 1652, though the dates are uncertain.
Anyway, back to the point. John is wearing his doublet or cloak off the shoulder and is revealing a high quality shirt with what appears to be an integral collar rather than a falling band with some nicely worked lace which appears to run around the band but also continues down the front opening. This was quite unusual as this sort of decoration would not be seen if the shirt was worn in the standard way under a buttoned up doublet. Perhaps it was an indoor shirt?