Technical requirements
Implementing PHOTARCH in a studio, museum, or field environment
One of the core strengths of PHOTARCH is its adaptability. The method is designed to work with a range of camera systems, lighting conditions, and institutional budgets — as long as its principles are respected. The method sets requirements for the picture, not for the camera: what a photograph is fit for is decided by measuring it. This page outlines what that measurement looks at, and the equipment that makes it easier to pass, from the board to lighting and colour calibration.
The board
The one piece of equipment the method cannot do without is the surface the object lies on. The PHOTARCH board is a calibrated white surface with markers in its corners. The application finds it in the picture, reads the markers, and derives how many millimetres one pixel covers on the board's surface — correcting the perspective in the same operation. The scale itself is taken first from the object: its longest side, measured with a digital caliper. The board gives the calibrated alternative and the perspective; a ruler in the frame is only a fallback (see Scale and Colour Control below). The file says which way its scale was set.
The board is not yet for sale. Until it is, the markers can be printed from the PHOTARCH app for a board of your own.
Camera & Lens
There is no required camera, sensor size or resolution. Any camera can be used; the grade each photograph receives says what it is fit for (see Nothing leaves unchecked below). A lens with low distortion, such as a prime or macro lens, makes that grade easier to reach.
PHOTARCH for iPhone is the camera built into the method: it photographs in RAW, HEIF or JPEG, sends each frame to the desktop as it is taken over the local network or a cable, and watches the board in the viewfinder — no board in view, board rectified — ready, markers found, but not a PHOTARCH board. Photographing when it reads ready is what gives the picture its scale. Pictures from any other camera are imported as files and graded the same way.
Scale and Colour Control
- The scale comes from the object's longest side, measured with a digital caliper; the board in the picture is the calibrated alternative, and corrects the perspective too. A ruler in the frame is only a fallback: it lies a few millimetres nearer the camera than the object's edges, which makes the object measure about one per cent too small
- The colour target is a ColorChecker (Classic or Digital SG), now sold by Calibrite, formerly X-Rite
- The Classic is enough to follow the method: it is the smallest and least expensive of the ColorChecker targets and is sold almost everywhere, so an institution, a unit in the field or a private photographer can have one at hand. The larger SG, with many more patches and its own ICC profile, is the chart Metamorfoze measures on, for flat originals
- Colour targets must be in the same light as the object
- Custom ICC profiles encouraged for optimal rendering
Consistent colour profiling ensures interoperability across platforms and time, especially when integrated with image databases or machine-learning datasets.
Software & File Format
- Capture in RAW format (e.g. .CR3, .NEF, .ARW)
- Post-processing in software that supports ICC workflows (e.g. Lightroom Classic, Capture One)
- Export the master as TIFF in Adobe RGB, at the depth it was photographed in; JPEG for access copies. The application asks for both, and says so when a file falls short of either.
- Embed EXIF/IPTC metadata directly or via sidecar files
All master files should be archived with non-destructive edits preserved. TIFFs may include embedded colour profiles and resolution metadata.
Bit depth
A picture is exported at the depth it was photographed in: 8 bits stay 8, and anything deeper — 10, 12, 14 or 16 — goes into a 16-bit TIFF, which holds it without loss, while the file's metadata says how many bits the camera recorded. PHOTARCH's levels go by that recorded number: at least 10 bits for a study, 12 for a reproduction. What bit depth means, what cameras actually record and how to make the most of it is under Bit depth for archival photography.
Nothing leaves unchecked
The PHOTARCH app checks each photograph twice. While it is taken, the Sharp, Exposure and Board lights say whether the middle of the frame is sharp, whether highlights are clipping and whether the board reads flat and square. Before it is exported, the app measures the scale, the resolution at the object, how much of the object is in focus and how much of it is clipped, colour against the ColorChecker, the bits the camera recorded and the format, and says what the picture is fit for — a record shot, a study or a reproduction — and what holds it back from the next level. What each level asks is under PHOTARCH's levels. For paintings, documents and other flat originals, FADGI, ISO 19264-1 and Metamorfoze can be turned on.
An Info panel says what the file itself carries — the scale and at which level, the metadata fields filled, the Content Credentials, the checksum and the rights — so that what is missing is missing on purpose and not by surprise.
Optional but Recommended
- Repro stand or tripod with geared column or rail system
- Grey card for exposure verification
- Backup system
Summary: minimum vs. recommended
| Component | Minimum | Recommended |
|---|---|---|
| Surface | White ground, digital caliper on the longest side | PHOTARCH board with markers |
| Camera | Any — the grade decides | Any — the grade decides |
| Lens | Any | Prime or macro, low distortion |
| Lighting | One LED panel | High-CRI LED or strobe with modifier |
| Colour | ColorChecker Classic | ColorChecker SG + ICC profile |
| Master | TIFF at the depth photographed | 16-bit TIFF in Adobe RGB, from a raw of 12 bits or more, or a 16-bit focus stack |
| Software | Adobe Camera Raw | The PHOTARCH app |
References
- standardISO 19264-1:2021. Imaging systems quality analysis — reflective originals.The device metrics FADGI and Metamorfoze align with. For flat originals, the PHOTARCH app reads its level through FADGI's correspondence; it does not analyse a test target.
- guidelineFADGI (2023). Technical Guidelines for Digitizing Cultural Heritage Materials, 3rd ed.
- guidelineMetamorfoze (2025). Preservation Imaging Guidelines, version 2.0 (first edition 2012). KB / Nationaal Archief.
- productCalibrite. ColorChecker Digital SG, replacing the X-Rite ColorChecker SG.
- researchKirchner, E. et al. (2021). Exploring the limits of color accuracy in technical photography. Heritage Science 9.Colour error under FADGI and Metamorfoze comes largely from dark patches — relevant to exposing for the object and lifting the ground to white.