Atrium (photography)
A halo is a photographic effect that occurs mainly in night photography and in situations with strong backlighting . Highlights get overexposure around the light source . The halo effect occurs equally in photography on film and in digital camera technology. In the case of digital cameras, one speaks of blooming .
In photography on film, a distinction is made between diffusion halos, which are created by chemical diffusion in the film, which thus causes overexposure around the light source, which slowly decreases towards the outside, and reflection halos, which are created by reflection of the light on the carrier layer of the film Form a halo ring around the light source. Diffusion halos have become smaller in modern films due to thinner emulsion layers ; against reflection halos, the carrier material is slightly colored (so-called gray base ) or, especially in the case of flat films or reversal films with a clear carrier, is provided with a reflection-reducing undercoating or back casting, which is discolored or removed during processing becomes.
The halo effect can be reduced somewhat by choosing a larger f-number . Correct night shots with direct backlighting require some photographic experience, as conventional exposure metering systems are not designed for such situations.
The halo effect can be created or enhanced using special effect filters .
Strong halo with direct backlighting against the sun
Diffusion light wells and ring-shaped reflection light wells (enlarged section)
Atrium due to strong brightness contrasts in black and white film
