This is one of my favourite kinds of light for this type of subject; bright, hazy overcast. There is enough blue in the sky to provide rich colour in the reflections, yet the direct sunlight is masked by the hazy cloud cover enough to give me rich shadow detail. A time exposure of 1/2 second provides the smooth textured water and the swirling patterns of foam.

The water of the river in this location is high in Tannin which means it is quite dark in colour. This helps make it look more blue because it reflects more of the sky that way.

The original photo has a bit more content on the right side of the frame, but that was cropped off in this calendar reproduction. The image has been quite popular with editors.

Leica R4, 28 mm lens, Kodachrome