Back light
Backlight is a term used primarily in photography for a light source that is directly in or near the direction of the subject.
Effects
Backlighting that falls into the lens of a camera has a number of effects on the resulting image:
- If the light from a bright light source hits the lens directly, a series of images of the aperture (usually round or hexagonal) will be visible on the image . They are caused by unwanted reflections within the camera and are differently pronounced depending on the quality of the lens and the reflections within the camera housing. This effect can usually be effectively reduced with lens hoods, but in some pictures such reflections are also used as a means of expression and artificially caused by filters.
- If the direct light source is covered by a part of the subject, this will appear too dark in front of a correctly illuminated background with automatic exposure measurement. This is why you should always use additional light sources (such as a brightener or a flash ) for backlit portraits if the face is to be recognizable. This is necessary even with high-quality cameras that recognize backlighting situations, as otherwise the background will be overexposed.
- In addition to this light-dark contrast, color contrasts are weakened so that images with faint colors can arise. The so-called fogging of the lenses in backlit situations also contributes to this.
- Transparent or partially transparent bright objects light up in the backlight, structures can become clear that remain hidden by the object surface in incident light .
Automatic programs of cameras rarely work satisfactorily with backlit shots. The automatically exposed images usually become too dark if the light source (s) are in the measuring range. If the camera allows it, we recommend multiple spot metering on areas that are important to the image, calculating an average value and setting the camera manually.
- Problems with backlit subjects
Brandenburg Gate Berlin, color reflections ( lens flares ) despite the remuneration
Extremely reduced colors, even on surfaces directly exposed to the sun on the Hohensyburg
Contrast-reducing reflections and light refraction in direct backlight
The sun shining through a leaf does not suggest a green leaf surface.
Yucca flowers glowing in the backlight
Illumination of leaves: too strong contrasts
Measurement of unwanted back light
The undesirable influence of backlight in photographic recordings is based on light sources outside the recorded image angle. It is possible the influence of such backlight metrological as stray light to be determined. For this purpose, for example, a dark subject can be photographed while a bright light source is positioned outside the field of view and pointed at the lens. In the ideal case, the light rays from this light source have no influence on the recorded image, but in practice these light rays are directed or diffusely reflected or bent within the objective and in the camera housing . The two images on the right illustrate a corresponding test setup and an image result with a relatively strong backlight influence without the use of a lens hood.
