Measured,
not imagined
Every look in Citus began as a real roll of film, or was built by hand with the same discipline. This page is the method, so it can be checked rather than believed.
The problem with "vintage"
A filter guesses. Someone looks at a few film photographs, decides what "film" means to them, and moves sliders until a picture feels right. The result is a mood, applied on top of a finished image, and it is the same mood on every frame.
Film does not work like that. A stock is a set of behaviours: how it maps the colours in front of it to the colours on the negative, differently in shadow than in highlight and differently for skin than for sky; where it stops recording more light and how gently; how its grain sits in the dark versus the light. Those behaviours can be measured. So we measured them.
01 · The rolls
Real film, shot on real cameras under controlled and ordinary conditions, then scanned. Not reference charts alone: skin, sky, foliage, hard light, the things a photographer actually points a camera at.
02 · The measurement
Each stock is characterised from the scans: its colour response across the range, the shape of its highlight roll-off, the size and distribution of its grain in shadow and in light. What the scan does not show, the look does not do.
03 · The reproduction
The measured behaviour is rebuilt as a look and rendered on the iPhone's own sensor image, live, in the viewfinder, before capture. Grain is generated into the image at capture, not laid over it afterwards.
Live, not after
The viewfinder shows the finished photograph, at preview rate, on the device. Nothing is uploaded and nothing is applied later. That matters for two reasons. You compose for the film you can see. And what you see is exactly the file you get.
The recipe travels with the photograph
Every photograph Citus takes carries its complete recipe inside the file, in standard EXIF that any photo tool can read: the look, the grain, every setting. Hand the file to someone and the recipe goes with it. Citus can lift a recipe back out of any of its photographs, and recipes can be saved and shared as small files.
What we do not claim
That any of it is film. It is measured behaviour, reproduced on a digital sensor, and it is only as good as the measurement. That every look is measured: some are handcrafted, built with the same method but from taste rather than a scan, and the app does not pretend otherwise. That it edits your existing photographs: it is a camera, not an editor.
What follows
A film lab, built the same measured way, from real glass and real film, follows as a free update. It will have its own page here when it ships, with its own measurements. Nothing on this page depends on it.
If you find something wrong in this method, write to support@citus.studio. Being checked is the point.