Halation

https://gyazo.com/c8fd8108ae92db9a83ee0bc8a6358862

Halation is the effect that occurs when the bright areas of an image appear to softly bleed around the edges of dark areas. This is caused by light going through the emulsion layer, bouncing off the base of the film and exposing the adjacent emulsion. Some film is manufactured with a black anti-halation coating on the base side.

Halation is the reflection of bright points of light off of the film base and pressure plate causing a “glow” in the strong highlights on some images. This is most evident when light sources are in focus in the photograph. Halation is a common characteristic of classic black and white photography and in some aerial photographic emulsions.

ハレーションは銀塩写真に特有な現象であり、デジタル写真では生じない

強い光源を撮影した写真において、光源の周りが広い範囲にわたって白くにじんでしまう現象、またはそのパターンのこと。写真乾板や写真フィルムの写真乳剤層を透過した光がフィルムやガラスの裏面で反射されて再び乳剤に戻ることを繰り返し、広い範囲を感光させてしまうために生じる。写真乾板とフィルムに特有の現象であり、CCDなどを検出器とするデジタルカメラでは起こらない。カメラレンズ内での多重反射が原因のフレアやゴーストとよく混同されるが、成因が異なる。

Halation refers to a phenomenon observed in celluloid film where intense light scatters within the film, leading to a secondary exposure. This effect predominantly impacts the red layer of the film, with some influence on the green layer, resulting in a characteristic reddish-orange glow around the light source. The precise tint of the halation can vary depending on white balance adjustments and color grading processes applied during post-production.

The anti-halation layer is typically applied to the rear of the film base, although it can also be found between the light-sensitive emulsion and the base itself. Its primary function is to inhibit light reflection from the back surface of the base or any objects located behind the film. This serves to counteract the halo-like effect known as halation. However, it’s worth noting that even with the presence of this layer, a faint halo effect might still occur since the anti-halation layer isn’t entirely opaque.

厳密には違うと思うけど、そう扱うことにする