Optical imaging techniques

Optical imaging analysis

Optical imaging techniques reveal details invisible to the naked eye, while respecting the integrity of the works.

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infrared

In-depth reading of the works thanks to optical imaging

Optical imaging offers a fine, non-invasive exploration of works of art, revealing elements invisible to the naked eye. It enables us to examine both surface layers (varnish, pigments, retouching) and underlying layers (preparatory drawings, repentirs, hidden signatures), without touching or altering the material.

Particularly well suited to paintings, wall frescoes, ancient manuscripts, decorated or polychrome objects, this imaging method helps to retrace the creative process, identify past interventions and better understand thestate of conservation.

It is a key first step in any study, restoration or authentication protocol.

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A non-invasive approach tailored to heritage requirements

A non-invasive approach tailored to heritage requirements

Optical imaging methods are non-destructive and non-contact. They respect the conservation constraints of old, fragile or unique works of art. Unlike chemical or physical analysis techniques, they require no sampling.

These tests can easily be integrated into cross-analysis protocols, notably with radiocarbon datingradiocarbon microanalysis or radiography. Together, these techniques offer a complete scientific reading of the object.

CIRAM performs these analyses:

  • In the laboratory, for transportable objects,
  • On site, with portable equipment, in museums, galleries, collectors' homes or on excavation sites.

A reliable, scientifically-proven mobile solution for heritage research and preservation.

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The main optical imaging techniques

01 - Visible light imaging

Visible light examinations are a fundamental first step in the analysis of works of art. They enable us to observe the physical characteristics, surface alterations and certain technical elements linked to the creation or conservation of the object. CIRAM uses three complementary types of imaging:

  • Visible-light photography for general observation of the work.
  • Grazing light, projected at 15°, to reveal surface alterations (cracks, blisters, lifting), substrate defects (cracks, tension, joints) and painting techniques.
  • Transmitted light, observed on the reverse side, to detect holes, tears and internal defects.

These techniques, which are entirely non-destructive, enhance the visual diagnosis and provide invaluable clues as to the condition, material history and manufacture of the works.

02 - Ultraviolet fluorescence

UV fluorescence imaging exploits the properties of certain pigments and varnishes to emit specific light when subjected to ultraviolet radiation. This technique is particularly valuable for analyzing paintings, manuscripts and polychrome objects.

It reveals essential information about the state of conservation of the works :

  • Identify restorations, overpaints and overcoats not visible in normal light,
  • Detect compositional variations in varnishes or surface materials,
  • Identify fluorescent pigments, useful for attributing or authenticating a work.

An essential diagnostic tool, UV fluorescence illuminates areas of interest to guide restoration work or alert us to any old interventions.

03 - Infrared reflectography

IR reflectography can be used to examine the deeper layers of a pictorial work using a high-definition infrared camera. By penetrating the upper layers, this radiation reveals what is invisible to the naked eye.

It is used for :

  • Identify areas for restoration and repainting,
  • Detect repentance and understand the successive stages of the artist's creative process,
  • View underlying drawings or preparatory sketches,
  • Verify the authenticity of a signature and detect forgeries.

The preferred tool of art experts, IR reflectography is an invaluable aid to authentication and the study of the creative process.

CIRAM, expert in optical imaging

For more than 20 years, CIRAM has been supporting museums, galleries, art market experts and archaeologists in their scientific heritage analysis projects. Thanks to a unique combination of scientific skills and state-of-the-art equipment, CIRAM guarantees examinations adapted to each work, whatever its format or state of conservation.

Technologies used include :

  • Visible light, grazing light and transmitted light,
  • UV fluorescence,
  • Infrared (IR) reflectography.

These techniques can be combined with each other or with complementary methods such as carbon-14 dating, pigment analysis, microanalysis or radiography. In the case of paintings, such cross-referencing is often necessary to confirm attribution hypotheses or reveal the exact nature of an ancient treatment.

Each intervention is accompanied by an illustrated scientific report, adapted to the challenges of conservation, authentication or enhancement of the work.

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Are you asking yourself these questions?

What kinds of objects can be studied using optical imaging?

Paintings, frescoes, manuscripts, decorated or polychrome objects.

Do these techniques risk damaging the works?

No. These are non-invasive, non-contact methods, perfectly suited to conservation requirements.

When should optical imaging be considered?

Before restoration, to guide interventions; during appraisal or attribution; or in a museographic or scientific context.

Can these techniques be combined with other analyses?

Yes, CIRAM combines optical imaging with other methods (dating, radiography, microanalysis) for a complete study.

Is it possible to intervene on site?

Yes, our teams travel with portable equipment and carry out analyses in situ, while respecting conservation conditions.

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