insects & light


Most animals can detect ultraviolet radiation, while mammals, including humans, have lost this ability during evolution. Butterflies and bees therefore see the world differently from humans: While long-wave red light can hardly be detected by insects, short-wave UV radiation plays an important role in their perception of the environment. Cameras and monitors are using the RGB (red/green/blue) colour space. In contrast, an insect would require a GBU (Green/Blue/UV) colour space. The eyes of birds are far better in discriminating colour shades because they see one "colour dimension" more. They are not trichromates, but tetrachromates (four colours: RGBU).

In UV photography, specific lenses and filters (such as Bader Venus filters) are mounted on a modified camera. This allows insights into a world that cannot normally be perceived by our human eyes – and this allows to explore many interesting research hypotheses beyond the restricted human perception. INSECTS& LIGHT accepts orders in the field of UV photography.

Regular RGB image and UV photo

On the left hand, a Violet Copper butterfly and a Neotropical wasp moth are shown as regular RGB (Red/Green/Blue) images. UV photography can produce a further monochromatic photo that displays information not seen by the human eye. The Violet Copper shows an intensive UV reflectance on the forewings. Photos contain standardized reflectance standards (10 and 95%).

False Colour Images

It is possible to get an impression of the insect's view of the world by creating false-color images. The three available colour channels (RGB of any display) are changed to represent new radiation spectra: The red channel is used to display “green” information, the green channel is used for “blue” information, and the blue channel is used for “UV” information. Everything is thus shifted towards shorter wavelengths. Images on the left hand side are regular RGB photos, images on the right hand side are GBU photos.

Most interesting in the GBU photos are those areas that appear blue and magenta, because this corresponds to areas with high UV reflectance. In many flowers,only little or no UV reflectance can be detected (e.g. corn flower, salvia). In some flowers like in mulleins, however, strong signals become visible. Particularly spectacular are sunflowers, Rudbeckia spp. and relatives. UV photography reveals that these flowers comprise two distinct colours, while humans can only see shades of yellow.

UV and Infrared (IR) Photography

While UV can be detected by most animals, infrared (IR) radiation cannot be seen; energy for these wavelengths is insufficient to trigger the neuronal receptors. Interesting and mostly beautiful images can nevertheless be achieved with IR photography. The examples below show a regular RGB image (left), a UV photo (middle) and an IR photo (right). UV and IR images differ drastically. UV radiation and blue light are scattered in the atmosphere, resulting in a bright sky. Long-wave radiation scatters far less, and this results in a deep dark sky in IR images. Vegetation mostly absorbs UV radiation (similar to sunscreen on the child's hand), but it reflects IR radiation. This produces the characteristic IR "snow-like images" in which trees look like on awinter morning after heavy frost. All images were taken on the island of Sylt, northern Germany.

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