# Film grain and halation > How film grain and halation work in xMosaique: four film-stock grain structures sized relative to the frame, and a red or orange bloom that only appears past a brightness threshold you set. Grain is one of four film-stock structures, applied at a size relative to the frame rather than to the pixel grid. Halation is a red or orange bloom that appears only past a brightness threshold you set. Both render in the viewfinder and in the saved file through identical maths, so what you frame is what is written. ## What the grain control actually does Four film-stock structures on a Fine, Medium and Coarse scale, with crystal size and clumping you can dial in separately. Clumping is what separates film grain from digital noise: real grain clusters, and evenly distributed speckle reads as a sensor problem rather than as a stock. A preset can bring its own grain settings with it — the amount, size and frequency fields Lightroom writes are read and applied — and the app's own controls sit on top of that. ## Why grain is sized to the frame Grain applied at a fixed pixel size looks completely different on a 12 MP frame and a 48 MP one: the same setting is coarse on the small frame and invisible on the large one. So the structure is scaled relative to the frame instead. A look you set up in the viewfinder holds together when the capture runs at full sensor resolution, which is the only way a live preview of grain is worth anything. ## What halation actually does Halation is the red-orange bloom film gets where a bright highlight scatters back off the base behind the emulsion — street lights at night, a window in a dark room, a rim light on hair. It is not a global glow. The effect applies only past a brightness threshold, which is what keeps it on the highlights that would really bloom instead of hazing the whole picture. ## Setting the threshold Lower the threshold and more of the frame blooms; raise it and only the brightest specular highlights do. Red is the more filmic of the two colours; orange reads warmer and holds up better against tungsten light. Because it renders live, this is a control you set by looking rather than by guessing — which is the whole argument for putting the grade in the viewfinder in the first place. --- ## Download on the App Store xMosaique is an iPhone camera app that applies Adobe Lightroom and Camera Raw XMP presets live in the viewfinder, before capture. - **App Store**: https://apps.apple.com/us/app/xmosaique-preset-camera/id6800525371 - **Price**: Free. No subscription, no in-app purchases and no ads. - **Platform**: iPhone - **Requires**: iOS 18.0 or later - **Current version**: 1.3.2 — 2026-09-07 - **Android**: In development. Not released, and there is no sign-up list yet. --- - Canonical HTML page: https://xmosaique.com/guides/film-grain-halation/ - This page in other languages: [Français (France)](https://xmosaique.com/fr/guides/film-grain-halation.md) · [Deutsch (Deutschland)](https://xmosaique.com/de/guides/film-grain-halation.md) · [हिन्दी (भारत)](https://xmosaique.com/hi/guides/film-grain-halation.md) · [Indonesia (Indonesia)](https://xmosaique.com/id/guides/film-grain-halation.md) · [Italiano (Italia)](https://xmosaique.com/it/guides/film-grain-halation.md) · [日本語 (日本)](https://xmosaique.com/ja/guides/film-grain-halation.md) · [한국어 (대한민국)](https://xmosaique.com/ko/guides/film-grain-halation.md) · [简体中文](https://xmosaique.com/zh-Hans/guides/film-grain-halation.md) · [繁體中文](https://xmosaique.com/zh-Hant/guides/film-grain-halation.md) · [Português (Brasil)](https://xmosaique.com/pt-BR/guides/film-grain-halation.md) · [Español (Latinoamérica)](https://xmosaique.com/es-419/guides/film-grain-halation.md) · [Español (España)](https://xmosaique.com/es-ES/guides/film-grain-halation.md) - All pages in this language: https://xmosaique.com/index.md - Consolidated brief (all pages, all languages): https://xmosaique.com/AI_info.md