Introduction

The Scientific Photography department at the Kunstmuseum Basel is dedicated to the imaging documentation of the museum’s collection. Its mission is to capture the objects of the collection in their material originality and to make them accessible to the public in the interest of preservation and mediation.

The department produces documentary photographs of artworks and installation views of exhibitions. As part of the conservation department, Scientific Photography is also involved in the museum’s research work, offering analyses through various imaging techniques that provide material-technological insights into the preservation and history of the artworks.

Documentation — whether by camera, 3D scanner, or spectrometer — is a translation from a physical object into a form of information. However objective and comprehensive the chosen medium may appear, every form of documentation is technically limited to a partial view and lossy in relation to the physical object. To make documentation consistent, comprehensible to third parties, and usable in the long term, working precisely according to transparently defined standards is essential. This document defines the fundamental standards for use at the Kunstmuseum Basel.

Fundamental Principles

Transparency: Documentary photographs should be produced in such a way that the visual character of the depicted subject is clearly discernible. This includes making the capture situation (camera position, lighting setup, etc.) evident — either from the image itself (e.g. a visible light source) or through a documented standard (e.g. raking light from the left). Technical metadata extends the information of an image file with non-obvious details. This includes basic technical information (e.g. creation date, creator) as well as descriptive information when images deviate from the standard (e.g. special image processing).

Reproducibility: Based on the transparent capture situation and the defined standards, an image capture can be repeated at a later point in time. This makes it possible to track and quantify potential change in an object.¹

Proportionality: Every documentation requires an effective balance between goal, effort, and benefit. Objects should not be captured at infinitely high resolution, but rather in proportion to the intended and foreseeable future use.² At the same time, the moment of capture also presents a potential for the preservation of an object, since any handling would almost inevitably — if minimally — alter the object. Each capture should therefore be preceded by careful consideration in order to avoid placing unnecessary burden on the object and resources.

Documentation / Standardisation: In principle, the technical and content-related requirements of the museum’s Medienstandard must be observed. By encoding the capture methodology and providing unique identification numbers in the filename, as well as using a standardised vocabulary of metadata, a digital file can be comprehended by third parties. Deviations from the Medienstandard and the specific standards defined here must be documented accordingly.

Standards

The following defines standards and best practices for various types of imaging.

Reproduction Photography

Reproduction photography aims to represent a depicted subject as close to real thing as possible. In the best case, a reproduction photograph of an artwork produces the same visual impression as the artwork itself. To achieve this in a verifiable manner, a visually known object is required that can be compared with its reproduction at any time as a neutral reference — a so-called target.

Where possible, at least one target should be included in each capture, so that the reproduction accuracy of the image can be measured quantitatively and evaluated qualitatively against the museum’s own tolerances and third-party standards.³

Processes & Responsibilities

Client: Photography commissions are accepted from the curators or conservators responsible for the object.

Photography commission: The desired views and capture types for each object are to be specified via the MuseumPlus form Fotoauftrag.

Timeline: Objects are typically photographed within one week of delivery. For larger consignments or special capture requests, specific timelines must be agreed in advance.

Transport: Objects are to be delivered together with a filled out form Fotoauftrag and collected within 2 working days after the capture is complete. Objects must be delivered in the condition in which they are to be photographed (e.g. unframed, unmounted, etc.).

General Capture Geometry

Neutral setup: For a neutral representation, the light should generally be aligned symmetrically to the optical axis.

Darkened capture space: The capture location should have walls, ceilings, and floors as dark as possible to reduce stray light and reflections. For strongly reflective objects, a black surface should be placed behind the sensor to avoid reflections and stray light.

Target: Targets should be placed in the same plane as the object (when possible) without casting a shadow on it.

Paintings

Capture geometry: Coplanar alignment of object and camera. Angle of incidence of light: 30–45°.

Light: As hard as possible and as soft as necessary. Typically 2–4 strip lights for even illumination. For highly glossy objects, light and lens should be cross-polarised.

Background: Black, matte (e.g. molton)

Crop: approx. 1–2 cm margin around the object. For the representative view (w11 – Hero Image) the work is cropped close to the visible dimensions so that no background is visible.

Views: Recto and verso. For decorative frames, additionally with frame. Stamps and inscriptions should be visible/legible.

Image examples – Paintings.

Works on Paper

Capture geometry: Coplanar alignment of object and camera. Angle of incidence of light: 30–45°.

Light: As hard as possible and as soft as necessary. Typically 2–4 strip lights for even illumination.

Background: L* 80, a* 1, b* 1, setup: acrylic glass (grey, matte, translucent, 3 mm opal satin)⁴ over grey board (L* 50, a* −2, b* −3)⁵

Crop: approx. 0.5–2 cm margin around the object. For the representative view (w11 – Hero Image) the work is not cropped so that the sheet edges are visible. Mounts are cropped where possible. Drawn borders on the mount are not cropped. Works mounted on multiple supports are cropped so that part of the largest support is still visible.

Views: Recto. Verso when inscriptions, stamps, etc. relevant to the object’s history are present.

Image examples – Works on Paper.

Sculptures

Capture geometry: Slightly elevated camera perspective.⁶ The target for determining a neutral setting should be placed as close as possible to the principal plane of the object.⁷

Light: Soft main light from front left. Fill light from front right.⁸

Background: For light-coloured objects: black, matte (e.g. molton). For dark objects: white/grey, matte.

Crop: approximately 10% of the object’s size as margin. For the representative view (w11 – Hero Image) the work itself is not cropped, only the target.

Views: Standard image generally centred from the front, object turned slightly to the left of the frame. Where possible, additionally capture all sides of the object. For special views and objects, consult with the curators responsible.

Image examples – Sculptures.

Installations

See Installation and Building Photography.

Technical Requirements

The requirements are based on the Metamorfoze standard Metamorfoze Preservation Imaging Guidelines (2012) and the FADGI standard Technical Guidelines for Digitizing Cultural Heritage Materials (2023), and have been simplified for practical use at the Kunstmuseum Basel.

• File format: TIFF, .tif
• Filename: according to Medienstandard
• Colour space: eciRGBv2 (RGB), Gray Gamma 2.2 (greyscale)
• Bit depth: 16 bit
• Tone curve: Linear, Linear-Scientific
• White balance tolerance: ΔE(a*b*) ≤2 (grey patches, ColorChecker Target)
• Exposure tolerance: ΔL*₂₀₀₀ ≤2 (grey patches, ColorChecker Target)
• Illumination homogeneity: ΔL*₂₀₀₀ ≤3
• Colour accuracy⁹: ΔE₂₀₀₀ ≤ 4 (average), ΔE₂₀₀₀ ≤ 10 (maximum)
• Resolution (minimum): >DIN A2: 150 dpi, ≥DIN A5: 300 dpi, <DIN A5: 600 dpi

Metadata

The following lists the metadata fields that should generally be filled in according to the controlled vocabulary. This list is based on the definition in Smithsonian, Basic Guidelines for Minimal Descriptive Embedded Metadata in Digital Images (2010).¹⁰ Fields marked with * are mandatory. Multiple values are separated by semicolons.

Installation and Building Photography

Installation photographs document the effect and installation of works in the exhibition space or at the location of their presentation, e.g. special exhibitions or collection presentations. Architectural photographs are distinguished from these when no artworks are depicted or they are not the central subject, e.g. architectural documentation or exterior views.

Processes & Responsibilities

Scope: Extensive rehangings of entire rooms are typically documented. Rehangings of individual works are documented on request.

Timeline: Extensive collection rehangings are typically documented within 4 weeks of completion of the installation on a day closed to visitors. Special exhibitions are independently documented typically within 3 weeks of the completion of the installation on a day closed to visitors. For large-scale exhibitions or concurrent openings/completions, specific timeframes must be agreed in advance.

Press images: Images (approx. 10) for advertising and journalistic purposes can be produced before the exhibition opening upon prior request. The corresponding walls/rooms must be fully installed. 1–2 days of processing time should be planned. The corresponding views must be agreed in advance with the Press/Communications department.

Aesthetic Requirements

Capture geometry: Camera at 150 cm height (approximately eye level). Converging verticals are to be avoided.

Light: Lighting conditions should be set as visitors would perceive them. Exhibition spaces with natural light should typically be photographed in daylight. With mixed light of different colour temperatures and intensities, the most intense light should be used as the basis for white balance and exposure. Big colour temperature differences should be corrected in post-processing.

Exposure: Brightness should be consistent across all views of an exhibition/series and appear as visitors would perceive it on site. The brightness of patch B4 (ColorChecker Target) at eye level should correspond to 75 L* (ΔL* ≤8).

Views: The spatial sequence and dramaturgy should be comprehensible from the views. Each work in an exhibition should appear at least once and, where possible, multiple times.

Image examples – Installation photography.

Technical Requirements

• File format: TIFF, .tif
• Filename: according to Medienstandard
• Colour space: eciRGBv2
• Bit depth: 16 bit
• Tone curve: Film Standard, Adobe Neutral
• White balance tolerance: ΔE(a*b*) ≤2 (patch B4, ColorChecker Target)
• Exposure tolerance: ΔL*₂₀₀₀ ≤8 (L* 75 = patch B4, ColorChecker Target)
• Image size (short side): ≥4000 pixels

Metadata

The general metadata requirements and recommendations apply.

Analytical Photography

Analytical photographs are created for documentation and research purposes. They go beyond reproduction photography by capturing or making visible specific material-technological properties of an object. These include not only ‹simple› detail photographs (e.g. signatures) but also specialist imaging such as infrared reflectography (e.g. to reveal carbon-based underdrawings) or X-rays (e.g. to examine paint layers). Since the technical settings vary considerably depending on the research question and object, they can only be standardised to a limited extent. All the more important, therefore, is the use of appropriate targets and comprehensive metadata that make the images comprehensible and reproducible.

Processes & Responsibilities

Client: Photography commissions are accepted from the curators or conservators responsible for the object.

Photography commission: The desired views and capture types for each object are to be specified via the MuseumPlus form Fotoauftrag.

Timeline: Objects are typically photographed within one week of delivery. For larger consignments or special capture requests, specific timelines must be agreed in advance.

Transport: Objects are to be delivered together with a filled out form Fotoauftrag and collected within 2 working days after the capture is complete. Objects must be delivered in the condition in which they are to be imaged (e.g. unframed, unmounted, etc.).

Visible Spectrum

In addition to standard reproduction photography, specific aspects of an object can be documented or made visible through different capture geometries and special imaging techniques.

Raking Light

To visualise the surface topography of an object, e.g. paper texture, raised paint layers.

Capture geometry: Light from the left, angle of incidence as flat as possible (1°–10°, depending on the object surface). Where possible, an additional capture should be made with the light rotated 90° to the first (from above/below).

Light: As hard and parallel as possible (point source or Fresnel lens).

Transmitted Light

To visualise the opacity of an object, e.g. watermarks.

Capture geometry: Light from behind.

Light: Softbox, light table, flash light box. The light should, where possible, be exactly masked by the object to avoid overexposure. Exposed light surfaces should be blacked out.

Coaxial Illumination

To visualise the reflection and gloss of an object, e.g. varnishes.

Capture geometry: Light hits the object along the same axis as the normal to the image plane (90°).

Light: As parallel and large-area as possible (Fresnel lens, softbox).

Technical Requirements

The requirements for standard reproduction photography apply in principle, along with the specific requirements for filters and spectra for multispectral imaging. Since very different settings and setups may be required depending on the object and research question, the standards should be understood as a starting point and basis. Deviations should be noted in the metadata.

Infrared Spectrum

To visualise underdrawings or differentiate between different materials.

Technical Requirements

The specific requirements for filters and spectra for multispectral imaging apply in principle. Since exact tonal reproduction may not be desired depending on the research question (e.g. making an underdrawing visible), the exposure tolerances should be understood as a starting point and guideline where possible. Deviations should be noted in the metadata. An additional standardised capture should also be made.

• File format: TIFF, .tif
• Filename: according to Medienstandard
• Colour space: Gray Gamma 2.2
• Bit depth: 16 bit
• Exposure tolerance: ΔL*₂₀₀₀ ≤2 (PTFE)
• Tonal accuracy¹¹: ΔE₂₀₀₀ ≤ 4 (PTFE) (average), ΔE₂₀₀₀ ≤ 10 (maximum)

Metadata

The general metadata requirements and recommendations apply. In addition, the capture parameters capture distance, aperture, focus setting, exposure time, illuminance, filter, and any processing steps must be recorded. Multiple values are separated by semicolons.

Ultraviolet Spectrum

To visualise fluorescences of an object, e.g. varnishes, material differentiation, mounts.

Technical Requirements

The specific requirements for filters and spectra for multispectral imaging apply in principle. Since exact tonal reproduction may not be desired depending on the research question (e.g. very low fluorescence), the exposure tolerances should be understood as a starting point and guideline where possible. Deviations should be noted in the metadata. An additional standardised capture should also be made.

• File format: TIFF, .tif
• Filename: according to Medienstandard
• Colour space: eciRGBv2
• Bit depth: 16 bit
• Tone curve: Linear, Linear-Scientific
• White balance tolerance: ΔE(a*b*) ≤2 (LOW A1, Target-UV)
• Exposure tolerance: ΔL*₂₀₀₀ ≤4 (LOW A1, Target-UV)
• Illumination homogeneity: ΔL*₂₀₀₀ ≤3

X-ray

To visualise the density distribution of an object, e.g. paint layer structure, material differentiation.

Technical Requirements

• File format: TIFF, .tif
• Filename: according to Medienstandard
• Colour space: Gray Gamma 2.2
• Bit depth: 16 bit

Metadata

The general metadata requirements and recommendations apply. In addition, the capture parameters current, voltage, exposure time, capture distance, filter, and any processing steps must be recorded. Multiple values are separated by semicolons.

Multispectral Imaging

Multispectral imaging refers to sets of images of an object captured across multiple wavelength ranges. A distinction is made between the emission spectrum of the light source and the capture spectrum of the camera. Based on the common photographically accessible spectra (UV, VIS, IR), various combinations are possible, e.g. UV-induced luminescence in the visible spectrum (UV emission → VIS capture) or infrared reflectography (IR emission → IR capture).

By keeping the camera and object stationary relative to each other during capture, the images can subsequently be aligned to pixel accuracy, processed, and selectively combined for further analysis. This enables deeper diagnostics of the works — for example in revealing watermarks or incised marks that would remain undetected due to specific properties of the works (lining, retouching, etc.), or in distinguishing different drawing and painting media based on their spectral characteristics.¹²

For standardisation and better comparability, the Kunstmuseum Basel follows the CHARISMA project with regard to the spectra and filters used.

Examples of multispectral imaging can be found here.

Technical Requirements

Targets

ColorChecker Classic Mini, X-Rite: This target should be used for all captures with standard illumination in the visible spectrum. The 24 patches cover typical colours and grey tones with relatively constant reflectivity across the visible spectrum. Due to its wide adoption, the target is particularly suited for comparing images captured at different points in time or at other locations with different capture parameters.

Where possible, individually measured spectral data of the specific target should be used for calibration.

Universal Test Target (UTT), TE262, Image Engineering: Multi-purpose test chart for evaluating the image quality of scanners and other digital imaging systems. The target contains patches for evaluating tonal values, colour reproduction, resolution, homogeneity, and geometric distortion. It is well suited for periodic quality checks of reproduction performance.

PTFE, artImaging: The five patches of this target cover tonal values with very constant reflectivity across a broad spectrum of approx. 250–2500 nm. It is therefore particularly suited for use in multispectral imaging and generally for captures involving light outside the visually perceptible spectrum.

Where possible, individually measured spectral data of the specific target should be used for calibration.

Target-UV, UV Innovations: For captures with light in the ultraviolet spectrum (<400 nm), this target may be used. Under UV light, individual patches fluoresce in greyscale tones as well as in the colours red, green, and blue, enabling the intensity and chromaticity of fluorescing material to be documented.

Where possible, individually measured spectral data of the specific target should be used for calibration.

Chrome ball: A highly reflective chrome sphere allows the capture geometry (e.g. the relative position of camera and light to the sphere) to be reconstructed. These balls are used among other things for creating Reflectance Transformation Imaging (RTI) captures.

Additional reference materials: Depending on the object under examination and the specific research question, it may be useful to include reference materials such as different drawing media or pigments for comparison beyond the standard targets.

Digital Image Analysis

After the systematic documentation of an object, images from the various capture methods can be selectively combined to make features such as watermarks, incised marks, and the surface topography of a work more visible. To this end, the colour values of two images can be added, subtracted, multiplied, or divided pixel by pixel.

For the mathematical operations, the colour values of a pixel are normalised: Black = 0 ≤ x ≤ 1 = White

Combining individual images can help to isolate specific aspects of a documented object. For example, subtracting a raking light image from a recto image results in a largely suppressed rendering of the drawing or print, while the surface topography of the object remains visible.¹⁴ Conceptually, an image subtraction reduces the image information that is contained in both images.

By the same principle, transmitted light images can be optimised through image computation: since in transmitted light all layers of an object are visible superimposed, subtracting the recto and verso raking light images yields a representation showing only the ‹middle› layers of the object.

Examples of image computation can be found here.

Metadata

The individual processing steps are to be recorded in the metadata so that they are comprehensible and reproducible. Multiple values are separated by semicolons.

Controlled Vocabulary

A controlled vocabulary is to be used for consistent and comprehensible technical and descriptive metadata. Multiple values are separated by semicolons.

Imprint

2026-08-20 / Version 1.1.1

Kunstmuseum Basel
St. Alban Graben 16–20
CH-4010 Basel
kunstmuseumbasel.ch

Max Ehrengruber
Scientific Photographer, Conservation
max.ehrengruber@bs.ch

Typefaces: IBM Plex Sans, IBM Plex Mono

Change History

The change history and previous versions are available at https://github.com/maxblumenschein/wfkmb/releases.

New in version 1.1.1:

• Added English version.
• Specification of cropping requirements for Works on Paper, in particular for works on mounts.

Terms of Use

The standard “Scientific Photography at the Kunstmuseum Basel – Standards” is published under a Creative Commons licence CC BY-NC-ND 4.0. The document may be shared under the following conditions: attribution “Scientific Photography at the Kunstmuseum Basel – Standards, Version 1.1.1”, no commercial use, no adaptations or modifications.