The Camera Scanning tab captures negatives with a tethered camera and imports them straight into NegPy. There is no separate capture app and no folder shuffling. It has two modes, and it selects between them from the hardware it finds.
Normal camera scanning. One exposure of the frame under whatever light you use, imported as an ordinary RAW and processed like any other file. This needs only a supported camera.
Narrowband RGB scanning. With an RGB Scanlight connected, the light flashes red, then green, then blue, and the camera takes one exposure per channel. NegPy's RGB Scan merge sub-pixel-aligns the three RAWs and assembles one frame before inversion.
Three shots beat one because a single broadband exposure lets each dye layer contaminate the neighbouring channels. The green Bayer filter is the broadest of the three, so it catches leakage from the red and the blue light at once. One narrow band at a time removes that crosstalk by construction, and every channel gets the full dynamic range of the sensor instead of sharing it.
| Camera | Any body libgphoto2 can drive with live view and remote capture. A body missing from that list often still works through the generic PTP driver. An a7C II does. |
| python-gphoto2 | An optional dependency, free software (LGPL). pip install gphoto2. |
| Scanlight (optional) | Needed for narrowband RGB only. Normal camera scanning works without it. |
NegPy runs well without any of this. Without python-gphoto2, the Camera Scanning tab shows a one-line setup hint, and every other part of NegPy is unaffected. Nothing proprietary is involved: libgphoto2 is LGPL, and no vendor SDK is bundled, linked or required.
⚠️ macOS and Linux only. libgphoto2 has no Windows build, so there are no Windows wheels and the tab cannot connect there.
uv sync --group camera # or: pip install gphoto2That is the whole install. libgphoto2 ships inside the wheel, so there is nothing else to
download, build or place. If you package the app yourself, run that same command before
make build. The build then bundles libgphoto2's camera drivers. Skip it and the packaged
app shows the setup hint.
Then put the camera in PC Remote mode and plug it in over USB. NegPy detects it automatically. There is no address to type, no login and no pairing.
On macOS, quit Preview, Photos and Image Capture first. The system's ImageCapture daemons hand a PTP camera to whichever of those apps is open, and libgphoto2 is then locked out.
Frame and focus. Open Live View & Scan. Click anywhere on the image to aim the camera's hardware focus magnifier at that spot. Click again to return to the full frame. In white-light and normal (camera-only) scanning, you can set ISO, shutter and aperture live from the toolbar. With a calibrated RGB preset those controls are hidden and locked to the preset instead (see Presets), so the scan cannot drift. A control the body cannot offer is greyed out. Aperture on a lens with no electronic diaphragm is the usual case, and that is most enlarging and macro glass.
Calibrate (RGB mode). Set the ISO and the aperture you will scan with. Press + beside the preset dropdown, place the small rectangle on the clear film base, name the preset and run it. The rebate strip between frames is an ideal target. Calibration meters that patch and solves one shared shutter plus a per-channel LED level, so each channel lands just under clipping. It records the ISO and the aperture with them.
That highlight matters, because the clear base becomes the black point after inversion. A clip guard therefore checks the raw Bayer photosites and backs the exposure off if any channel saturates. Save the preset once per film stock and reuse it.
If the target is unreachable at your exposure, the run stops at the probe. A pop-up says which way to adjust: over-exposed means close the aperture or lower the ISO, under-exposed means open up or raise the ISO. No preset is saved. Adjust and calibrate again in the window that stayed open.
Presets. A selected preset is shown read-only, with its RGB levels, ISO, shutter and aperture. The scan forces that exposure on the body before every frame, so a bumped dial cannot falsify the result. To build a preset by hand instead, pick Create a manual preset… from the dropdown. The sliders and the exposure steppers unlock. Dial them in, then press the save (floppy) button to name and store the preset. White is the white-light preset's channel only, because the Scanlight cannot light it together with RGB.
Scan. Pick an output folder and a preset, then press Scan for each frame. Files land in a per-roll subfolder, auto-numbered, and are imported and merged automatically, so the inverted positive appears a moment after the shutter. Retake re-shoots the current frame without advancing the counter.
Narrowband Scan. Scans lit by narrowband RGB LEDs render more saturated than white-light scans, because each channel samples its dye near the absorption peak and the natural spectral overlap of broadband light is missing. The Narrowband toggle in the Process panel, beside Linear RAW, corrects this with the bundled RGBScan input profile, in the preview and in every export. An explicit Input ICC in the Export settings takes precedence while it is set.
A single-shot scan under a narrowband RGB source can come out with hues that no slider fixes. Yellows drifting orange is the classic sign. The cause is sensor crosstalk: the camera's color-filter passbands overlap the source's bands, so the green pixel sees the blue LED and some red, and every channel carries a share of its neighbours. It is a fixed property of your sensor and light pair, independent of the film.
To correct it, photograph the bare light three times with no film in the holder: red only,
green only, blue only. Use the same settings you scan with, exposed just below clipping.
Then open the Calibration panel, find Trichrome Calibration, press the calibrate
button, pick the three captures, name the profile and save it. The selected profile un-mixes
every scan with a 3×3 matrix in the linear domain, before inversion. Profiles are TOML
files in the NegPy/sensor folder. Re-run Batch Analysis after you change the profile.
Do not use it on RGB-triplet (trichrome) scans. They are crosstalk-free by construction, because each channel comes from its own single-light exposure, and NegPy skips the correction automatically for triplet assets. A dedicated film scanner has no sensor crosstalk either: a Coolscan's mono CCD reads one LED at a time. Its residual color error is film-dye crosstalk, which the density-domain Crosstalk matrix handles (see CROSSTALK.md).
| Symptom | Cause | Fix |
|---|---|---|
| The camera dot shows "in use" (amber hint) | An ImageCapture app holds the body. Only one program may claim a PTP camera. | Quit Preview, Photos and Image Capture. Preview is the usual culprit, because it grabs the camera silently. NegPy reconnects on its own once the camera is free. |
| No camera found, and nothing else is running | The body is not in PC Remote mode, or it is a mass-storage/MTP connection. | Set the camera's USB connection mode to PC Remote. |
[-10] Timeout reading from or writing to the port, and no other program holds it |
A program crashed while connected. The camera still thinks the session is open and refuses a new one. | Power-cycle the camera, or unplug and replug the cable. Nothing on the computer fixes it. |
| Live view is black | The body dropped out of PC Remote, or the lens cap is on. | Power-cycle the camera. |
| The scan window opens with "no live view" instead of a preview | libgphoto2's entry for this body has no preview capability. Either the body genuinely lacks it (Sony a6000), or it is connected in MTP mode, where no body has it. | If the message names MTP, set the camera's USB mode to PC Remote and reconnect. If not, this is expected. Scanning works normally, but you must set framing and focus on the camera, and calibration is unavailable because it aims through the live view. |
| Capture says the camera returned JPEG instead of RAW | The camera's image-quality setting is JPEG, or RAW+JPEG selected the processed file. | Set image quality to RAW only, then retry. |
| The aperture stepper is greyed out | The lens has no electronic diaphragm. | Expected. Set the aperture on the lens itself. |
| A setting snaps back to its old value | Property writes are asynchronous, so the body needs a moment. | NegPy polls until the value lands and logs a warning if it never does. If it never does, that setting is not writable in the body's current mode. Try M. |
| The Scanlight is not detected | Wrong USB-C port. | The Scanlight has two ports and only one carries data. The other is power only. Use the data port. |
- USB only. libgphoto2 can reach some cameras over the network, but not Sony bodies. The tab is a tethered-USB workflow.
- Only Sony bodies are tested, because that is the hardware on hand. Nothing in NegPy
assumes a vendor: every control is looked up rather than assumed.
isoandshutterspeedare named the same everywhere. The aperture isf-numberon Sony and Panasonic, andapertureon Canon, Nikon, Fujifilm, Olympus and Sigma. The RAW suffix comes from the camera, and the still is taken into memory rather than onto a card. Canon and Nikon default to the card and will not shoot without one. Reports from other brands are very welcome. - The focus magnifier depends on the vendor. Sony packs the zoom ratio and the target
point into one property, so a click both magnifies and aims. Canon (
eoszoom) and Nikon (liveviewimagezoomratio) split them, and their coordinate space is unknown here, so a click magnifies where the body already looks. Every other body has no magnifier at all, and the feature disables itself. - Tested on macOS. The Python is portable and libgphoto2 is a Linux-first project, so Linux should be at least as good. This is unverified.
- Speed. A three-shot RGB triplet takes about six seconds on an a7C II over USB. Almost all of that is the body's per-image transfer latency, not the file size. Stills are taken inside the running live-view session, so there is no per-frame reconnect.
- Credit. The R/G/B sequencing and the exposure-calibration approach come from rohanpandula/TriRGB. The light is jackw01/scanlight. The camera is driven through python-gphoto2. The narrowband approach follows Flückiger et al.'s work on trichromatic film scanning.