Quick primer: Halation is that glowy halo effect you get around bright light sources in photos, especially with film. Light bleeds through the film and bounces back, creating this soft dreamy glow around highlights. Very analogue, very nostalgic.

This slider controls how much of that effect shows up in your images, from almost none at -10 to absolutely drenched in glow at 10. At the negative end, things stay clean and crisp without that atmospheric bloom. Slide it positive and you start getting that signature film look, soft halos around lights, an overall dreamy quality, that whole romantic vintage vibe.

Range: -10 (minimal halation) to 10 (maximum glow)

The positive end is pretty strong, like it really commits to the effect. And yeah, it's going to mess with both your lighting and your composition because halation doesn't just add glow, it fundamentally changes how light behaves in the image. Highlights bloom differently, shadows respond to that spill, the whole spatial relationship of elements shifts a bit to accommodate all that atmospheric haze.

If you're going for that dreamy film aesthetic, crank it up.