Päivänvaloyksikkö

Päivänvaloyksikkö is a Finnish term that translates to "daylight unit." It refers to a unit of measurement used in photography and lighting to describe the color temperature of light sources. Specifically, it represents the color of light as it appears around noon on a clear day.

The color temperature of light is measured in Kelvin (K). Standard daylight has a color temperature of approximately 5500 K to 6500 K. Light sources with a lower Kelvin value appear warmer (more yellow or reddish), while those with a higher Kelvin value appear cooler (more blue).

In photography, understanding the color temperature of light is crucial for achieving accurate color reproduction in images. Different light sources, such as incandescent bulbs, fluorescent lights, and natural sunlight, have different color temperatures. If a camera's white balance setting does not match the color temperature of the light source, the resulting image may have an undesirable color cast. For example, shooting under incandescent light (around 2700 K) without adjusting white balance will make the image appear too yellow.

Photographers often use a "daylight" white balance setting on their cameras when shooting in natural sunlight to ensure that white objects appear white in the photograph. Alternatively, they can manually set the white balance by photographing a white or gray card under the prevailing light conditions. Film also has different ISO ratings for daylight and tungsten (indoor artificial light), reflecting the need to compensate for different color temperatures. The concept of "daylight unit" is therefore fundamental to achieving natural-looking colors in visual media.