The raw file is the negative
Keep it, never rewrite it, and never let a cloud service hold the only copy. Three copies, one of them offline, is the whole backup policy. The JPEG is a delivery format; the raw plus its sidecar is the archive.
Open-source photography · Raw · Colour
Photography you can develop, prove and print
Everything after the shutter can be open. Raw conversion, cataloguing, pixel editing, colour management, printing and the metadata that shows what you actually did — all of it runs on a stock Linux desktop with software you already have. This track documents that pipeline, and is honest about the part of a camera that is still closed.
RawThe negative stays yours
16-bitSensible working depth
ICC v4Colour is a measurement
0Subscriptions required
01 · Principles
Three rules that keep a photograph yours
The tools are free, but the discipline is what makes the result reproducible. These three rules apply whether you are shooting a product, a landscape or a building survey.
Colour is a measurement
Profile the display, work in a defined space, and convert with an embedded profile at export. A photograph that only looks correct on the laptop that produced it is not finished — it is an accident that has not been discovered yet.
Metadata is documentation
EXIF and IPTC record what the camera did; a short text note records what you did. Strip location before publishing to strangers, keep it in your own archive, and say which of the two you shipped.
02 · Workflow
The pipeline, from card to print
Five stages, each with a free tool that does the job properly. Nothing here rewrites an original file, and every stage leaves behind something a colleague could pick up.
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Ingest and verify
Copy with
rsyncor a dedicated importer, verify checksums, and keep the card untouched until a second copy exists. Rename on ingest, never later; renaming a catalogue of ten thousand files is a project, and a boring one. -
Catalogue
digiKam or an equivalent keeps keywords, ratings, faces and geodata in a database beside the files. Treat the database as an index you can rebuild, not as the place the photographs live.
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Develop
darktable or RawTherapee reads the raw and writes a sidecar; the original is never modified. Work scene-referred first — exposure, white balance, tone — and only then reach for the look.
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Pixel edit, when it is genuinely needed
GIMP or Krita for retouching, compositing and masks. Keep the layered source file next to the export, because the flattened result will not explain itself in two years.
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Export, convert and document
Convert to the destination profile with a stated rendering intent, size and sharpen for the medium, and write down what you did. The export is not the archive.
| Job | Package | What it gives you |
|---|---|---|
| Raw development | darktable, rawtherapee | Non-destructive raw conversion with sidecar files; darktable for scene-referred workflows and a large module set, RawTherapee for a more traditional, demosaic-first approach. |
| Catalogue | digikam | Keywords, ratings, face and place data, batch operations and export presets — the library index, on your own disk. |
| Pixel editing | gimp, krita | Retouching, masks and compositing; Krita when the work is closer to painting or when 16-bit floating point matters. |
| Metadata | libimage-exiftool-perl, exiv2 | Reading, writing and stripping EXIF, IPTC and XMP in bulk — including removing location data before you publish. |
| Conversion & batch | imagemagick, gmic | Profile conversion, resizing, watermarking and scripted batch work; G&MIC adds a serious filter library on the command line. |
| Colour management | argyll, displaycal | Build and inspect ICC profiles with your own colorimeter, and calibrate the display you are actually judging on. |
| Panorama & HDR | hugin, enblend, enfuse, luminance-hdr | Stitching, exposure blending and tone mapping, with control over the projections and the seams. |
| Capture & tethering | gphoto2 | Remote capture, interval shooting and file transfer from a long list of cameras, scriptable from a shell. |
| Print & vector | inkscape | Print layouts, marks and light plots — anything where vector output and exact dimensions matter. |
03 · Colour
Colour management without the mystique
Colour management is three measurements and a convention: profile the display, work in a defined space, convert on export to the space the destination expects. Everything else is a detail you look up when the measurement asks for it.
- Profile the display with a hardware colorimeter and re-check it monthly; an uncalibrated screen is a rumour with a backlight.
- Keep working space explicit. A wide-gamut working space is fine as long as the export states what it is; sRGB remains the safe destination for the web.
- Soft-proof before printing against the printer profile, and accept that the paper will not glow like the display.
- Record the intent. Perceptual for photographs, relative colorimetric with black point compensation for proofs and charts.
Tooling
Measure, then convert
# build a display profile (ArgyllCMS + a colorimeter)
dispcal -v -o my-display
dispread -v -k my-display.cal my-display
colprof -v -qh -aG my-display
# inspect what a profile is actually capable of
xicclu -ir -pl my-display.icc
# convert for delivery: source profile, then destination
magick print.tif -profile sRGB.icc -profile printer.icc \
-intent perceptual out.tifImageMagick applies profiles in order: attach the source, then convert to the destination. Never assign a profile to fix a wrong one — that only relabels the problem.
04 · Hardware
Open hardware, and the honest caveat
No mainstream camera body is open hardware. Sensors, image processors, lens protocols and the firmware that drives them are closed, and saying otherwise would be a lie told in a friendly tone. What can be open is everything downstream — and a surprising amount of the hardware around the camera.
Single-board cameras
Raspberry Pi camera modules with the libcamera stack give you a documented sensor pipeline, interchangeable C and CS lenses and a board you can replace for the price of a filter. For timelapse, monitoring, macro rigs and teaching, that is often enough camera.
Magic Lantern and CHDK
Community firmware adds raw video, intervalometers, focus stacking and zebras to a range of closed cameras. It is reverse-engineered, it voids warranties and it can brick a body: read the compatibility list, update the stock firmware first, and never use it on the only camera you own.
The ecosystem around the body
Printed brackets and lens caps, Arduino intervalometers on the remote shutter port, open lens adapters, DIY light meters and calibration targets. The camera is the closed part; everything you bolt to it does not have to be.
Why we still document it. The value of an open pipeline is not ideological, it is practical: your archive stays readable when a company changes its subscription model, your edits stay inspectable, and your colour decisions can be reproduced by somebody else. That is the same argument we make for open hardware in networking and audio.
05 · Ethics
What a photograph asserts
Editing tools have never been more capable of inventing detail. That makes the documentation of what was done part of the craft rather than an optional footnote.
Consent and privacy
Publishing a photograph of a person and publishing their location are two different acts. Ask when it is a portrait, strip geodata when the subject is a private place, and treat photographs of children as a category of their own rather than a subset of street work.
Metadata on export
Write a small script that strips GPS and serial numbers for public exports while keeping
them in the archive copy. exiftool does this in one line, and the difference
between the two files should be a decision you made, not an accident.
No invented detail
Generative fill, upscaling and “enhance” features change what the image claims happened. Used as a tool, disclosed, they are legitimate. Used silently in documentary work, they are a fabrication — and with metadata, the disclosure is one field away.
Fidelity over fashion
A print that matches the screen and the scene will still look right in ten years. A grade that matches this season’s timeline will not. Keep the neutral version of every frame; the look is a layer, not the negative.
06 · The guide
Where to start
The raw workflow end to end
One frame, from card to print, with every command and every decision written down — the reference we build the rest of the track on.
Colour management for the rest of us
Profiling a display, choosing a working space, soft proofing and the three settings that actually change a print.
Firmware, boards and accessories
What is worth doing with open firmware, which boards make usable cameras, and the accessories we have actually built and broken.
Contact
Send us a frame
A raw file that no converter handles, a profile that measured wrong, a firmware build that bricked something, or a correction to this page. Include the camera, the firmware version and the command you ran.
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Graphics & photography
gfx@polymathes.ccWeekly on the mailing list -
Corrections & errata
errata@polymathes.ccReviewed in public