{"id":186,"date":"2020-03-08T03:34:00","date_gmt":"2020-03-08T03:34:00","guid":{"rendered":"http:\/\/hb-themes.com\/themes\/highend\/online-shop\/?p=186"},"modified":"2020-03-09T01:01:03","modified_gmt":"2020-03-09T01:01:03","slug":"halation-film-stock-digitally-imitating-color-grading","status":"publish","type":"post","link":"https:\/\/tobiasdeml.com\/cinematography\/halation-film-stock-digitally-imitating-color-grading\/","title":{"rendered":"Halation on Film & Digitally Imitating It"},"content":{"rendered":"

Halation is an effect that occurs only with film stock, never in digital cinema. To understand it, you have to peel back some of the layers – quite literally – and understand some physics.<\/p>\n

How Does Halation Happen?<\/h2>\n

Color film stock<\/a> is composed of many different layers<\/a> – but speaking on simple terms, color film usually has 3 layers of differently color-sensitive emulsion and an anti-halation backing. The color layers are self-explanatory; all of them consist of silver halide particles that are sensitive to a certain wavelength of light, get exposed by the process and turn the photon energy entirely into chemical energy (which darkens the particles as they absorb the light), thus creating a 3-layered “picture”. When those layers are combined, they result in a color negative, and when you print them to a positive, the color image represents the reality that was in front of the lens.<\/p>\n

Now, that’s all pretty Film School 101. But what about this mysterious last layer, the anti-halation backing? Well – when you have a strong source of light (such as outside daylight when shooting inside), it penetrates all three layers and only gets partially absorbed along its path – but it is so strong that it maxes out the absorption abilities of the particles. That results in what we call “blown out” areas of the image, usually completely white.<\/p>\n

\"Halation<\/a>

Halation effect – the light penetrates blue, green and red layers on the film stock, then only partially gets absorbed by the anti-halation backing, bounces back into the red layer and creates halation.<\/p><\/div>\n

But since the energy wasn’t absorbed entirely, that left-over light would now hit the semi-shiny mechanics of the camera body, and scatter<\/a> back into the film emulsion in a chaotic way. This diffuse reflection<\/a> is usually undesirable and called “Halation<\/em>” – it creates a halo-like image within the image.<\/p>\n

So, to avoid this, film manufacturers added an anti-halation layer that had the role to absorb all that left-over light. Well, not entirely…
\nReally strong light rays are so strong that they partially bounce off the anti-halation layer and scatter back into the last layer, namely the red one. This is the reason for the distinct redness of “classic” film halation.<\/p>\n

Steve Yedlin has a nice example of Halation in his “On Color Science<\/a>” article, and here’s another one<\/a>.<\/p>\n

Here’s a video example of “regular” halation on film stock, film stock + diffusion, and a modified stock with the anti-halation layer removed:<\/p>\n