Natural Light Levels and Characteristics

The colour of natural light changes according to depth: warm wavelengths are absorbed quickly as the depth increases. Unlike the South, absorption is not necessarily the main factor behind tones at greater depths in Finland, where the water is often so strongly coloured that it dictates the colour of natural light. For example, the colour of Finland's lake waters varies from dark brown to bright turquoise. In the western part of the Gulf of Finland and the Archipelago Sea, surface water is often surprisingly turquoise in colour, quite unlike the green shades in the east of the Gulf and the Bothnian Bay's russet tones.

If warmer wavelengths are absent or insufficient in natural light, the photographer can use a flash to bring the subject's colours to life. In Finland in particular, balanced lighting is often achieved by using the prevailing light alone for landscapes, giving a more impressive result than a combination of prevailing light and a flash, which tends to illuminate underwater particles. In most cases, prevailing light leads to the capture of more dynamic scenery and brighter water. On the other hand, in close-ups a flash almost always works well, beautifully bringing out the subject's colours. This is because there is little water, and therefore fewer particles, between the lens and subject. However, even the most powerful flashes are insufficient at distances of a few more metres.

In conditions of high visibility, natural light is surprisingly plentiful under the surface of lakes and the Baltic Sea. The light level depends on depth, visibility and water colour. At relatively shallow depths, particularly in bright sunshine, the following exposure settings can typically be used for landscape photography: an ISO sensitivity of 100, an f/8 aperture and a shutter speed of 1/100 s or faster. An ISO sensitivity of 100 will often suffice even when under ice and shooting upwards into slightly diagonal light. However, in Finnish waters, natural light seldom suffices 20–40 metres deeper.