Community firmware unlocks open‑gate 3:2 CinemaDNG on the SIGMA fp

A community release has opened up a new recording mode on the SIGMA fp that captures CinemaDNG RAW across the camera’s full 3:2 sensor area. The unofficial build adds an around 3000 x 2000 open‑gate option that records CinemaDNG RAW using the entire full‑frame imaging area rather than the usual 16:9 window.

The initial prototype came from developer Vitaly Li and was shared inside a SIGMA fp user group on Facebook. That experimental code has been taken up by the fpSup project, which now offers an open‑gate release named OG3K. The fpSup distribution is currently tagged v0.2.3a and is described as an alpha release.

OG3K stores a 3024 x 2010 raw frame and sets a default DNG crop of 3008 x 2000. It lets shooters choose 8, 10 and 12‑bit CinemaDNG files and exposes a range of capture speeds: the build lists eight frame rates from 23.976 to 100fps. For many users the target format will be 24fps 12‑bit CinemaDNG written to an external SSD via the camera’s USB‑C port.

Aside from the change in aspect and file format, the mod also affects the sensor readout. fpSup’s documentation shows a shorter rolling shutter interval for the OG3K release: 12.44 ms, compared with the camera’s stock UHD CinemaDNG readout at 21.1 ms. That shorter read time can reduce skew and motion artifacts when compared with the stock readout window.

Data rates are provided in fpSup’s notes. At 24p the open‑gate 3K in 12‑bit is listed at roughly 220 MB/s; the same frame rate and resolution in 10‑bit and 8‑bit are shown at 184 MB/s and 148 MB/s respectively. The team’s tests also measured an SSD using the camera’s USB‑C port hitting about 390 MB/s, a figure the developers attribute to the 5 Gbps USB 3.0 link rather than the drive itself.

Vitaly Li ran a capture example that lasted 18 minutes and, using the 220 MB/s figure for 12‑bit, that duration would translate to roughly 240GB of data. The developer does not specify which particular drive that total refers to. fpSup additionally supplies an SD‑only build called OG2K for users who prefer to record to SD media; OG2K keeps the same field of view but outputs 2016 x 1344 at a listed 98 MB/s in 12‑bit at 24p.

When it comes to resolution and pixel count, the open‑gate frames are smaller in pixel dimensions per frame than UHD. The stored 3008 x 2000 DNG equates to about 6 megapixels per frame, while the camera’s UHD window holds about 8.3 megapixels. In short, the mod trades some pixel count for access to the full 3:2 sensor area and its framing characteristics.

Both OG3K and OG2K are distributed free of charge. There are important prerequisites: each build requires a SIGMA fp running firmware Ver.5.02, and the fp L variant is not supported. The releases have been tested only on Ver.5.02, and the project authors make clear that these builds are not finished — they are experimental work.

The developer’s caveat is explicit: "Use at your own risk; it is still a work in progress." That warning sits alongside two other cautionary notes used by the project: "This article is NOT encouraging anyone to use unofficial or unsupported firmware on their SIGMA fp cameras." and "Installing such firmware is at your own risk!" The community and the developers advise caution: installing unofficial code can carry risks for the camera and its warranty, and users should understand the potential consequences before proceeding.

For shooters interested in trying the builds, check that your camera is running Ver.5.02 and that you accept the experimental status of the code. The documentation supplied by fpSup contains the technical details on frame sizes, bit depths and data rates; it also lists the supported frame rates from 23.976 up to 100fps. Because the project is community‑driven and the code is labelled alpha, expect ongoing changes and iterations rather than a polished, final firmware package.

The OG3K work is notable because it opens the SIGMA fp to a different way of using its full‑frame sensor, and because it demonstrates what a small, dedicated developer community can achieve when it focuses on raw output and readout behaviour. For many shooters, the tradeoffs — fewer megapixels per frame but a broader field of view and a faster readout — will be worth exploring in test shoots rather than critical production environments.

If you experiment with either build, be sure to keep backups, use tested media, and accept that the software is not an official SIGMA release. The community’s notes and the developer’s example captures provide useful starting points for assessing storage needs, required data rates and matching external recording hardware to the fp’s USB‑C throughput.