What is the Anti-Halation Layer in Film?

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Have you ever noticed a red halo around the highlights in photos when you use certain film stocks? This feature is either loved or hated by photographers. It can be off-putting when it is too pronounced, while on some images, it can add an extra touch of magic that sets your photo apart. But what causes this unfamiliar effect to show in your photos?

This effect appears in film stocks meant for motion picture film. There is an extra layer in the film emulsion, called Anti-Halation, designed to avoid excessive reflection bouncing from the rear part of the camera with the constant motion of the film. This layer is usually positioned at the end of the emulsion composition, capturing the light going through each layer. However even though the halation around the reflective surface is reduced, it is not completely removed.

Credits: twlkk, appleman35mm, aciano, mkeene & fishmonkeycow

When we take this layer off the emulsion composition, the halo is much more pronounced, especially from the red layer. Hence the red halo appearing around the highlights, the most sensitive area of the film where light can bleed easily. The anti-halation layer varies across different film stocks.

In black and white film stocks, this layer is water-soluble. Many photographers pre wash their films before developing them to eliminate this layer. In color film, the anti-halation layer is not water-soluble, so in C41 chemistry, the bleach and fix steps are designed to remove the anti-halation layer.

Credits: fabio_corsatto, david_peach, thehenrydemos, natalie_93 & jeni3

Do not confuse the anti-halation layer with the rem-jet layer. The anti-halation absorbs light, while the rem-jet layer (specific to certain films), is a black, photo carbon-based layer, coated on the front side of the film (the side facing the lens).

The rem-jet (removable jet black), as well as functioning as anti-halation, is antistatic and protective. It prevents electricity from building up while the film runs through the machine, and its dark color protects the film from light leaks when it is loaded onto the camera.

If you self-develop motion picture film, it is possible to remove the remjet layer by pre-soaking your film with warm water and baking soda to make the water alkaline. The ratio is 15 g of baking soda for 500ml of water, then soak for about one minute in warm water at 40°. Wash until the water runs completely clear, then proceed to develop your film as usual.


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written by eparrino on 2024-03-30 #gear #anti-halation-layers #rem-jet-layer #red-halo #motion-pictures-film

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2 Comments

  1. hervinsyah
    hervinsyah ·

    Regret I used my only High ISO, Fuji ISO 1600 not at the situation like this 😭

  2. stereograph
    stereograph ·

    I never liked this red halo effect,
    i like to experiment with remjet removal in my lab.
    sometimes before dev, but mostly after, the results are different!
    last thing to do, is to remove the remjet before exposure,
    but i have no idea how to do this without sitting ducks in the darkroom
    for hours until the film is dry. :-)

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