• Ketel introduced the full-length group portrait format to the Dutch burghers with great success, to have been mostly commissioned as a portraitist.
• He also painted some religious subjects.
• His pupil was the Danish-born
Pieter Isaacsz, and
Wouter Crabeth from Gouda. • After the death of wife in 1602, he remarried in 1607 to Aeltge Jans.
• Ketel suffered a stroke and made his will in November 1613, witnessed by Hendrick de Keyser.