In the 1640s and '50s a number of innovations were rather suddenly introduced at Delft in the painting of architecture, townscapes and genre scenes. We would like to shed some light on these revolutionary developments, not from the perspective of any one artist, but from that of a like-minded group,. Although art historians have discredited the notion of a 'Delft School', there can be no quesstion that the artists in this city did have a number of interests in common, such as optics, light, colour, composition, perspective, and the city as a backdrop for their portraits of daily life. Around the middle of the century the provincial, somewhat derivative character of local painting was transformed and Delft rapidly evolved into an influential centre of art. This transformaton manifested itself first of all in the work of painters who settled here in the period 1645-1675, some for a shorter, others for a longer time. These painters still number among Holland's most fam