Behind the Lens: Digitising Cultural Heritage at The Photographers’ Gallery

On the 11th April, a presentation at The Photographers’ Gallery pulled back the curtain on a part of photography most people never see: the meticulous, highly technical world of cultural heritage digitisation. Led by John Wallace, the session challenged a common assumption - that digitisation is simply about taking a good photo - and replaced it with something far more rigorous.  

It’s Not Photography, It’s Measurement

The talk highlighted the difference between artistic photography, which values mood and interpretation, and heritage imaging, where these instincts can be counterproductive.

As highlighted in the presentation, the goal is accuracy, capturing an object exactly as it exists, with no creative interpretation or distortion. That means controlled lighting, calibrated equipment, and measurable outputs. As noted in the opening slides, heritage imaging is about “recording the object as realistically and accurately as possible with known standards and targets”. It’s less about making something look good - and more about making it true. 

Two Worlds: Reflected vs Transmissive

 A key concept explored during the session was the difference between reflected and transmissive materials- something that fundamentally changes how you approach capture.

• Reflected materials (books, prints, paintings) rely on light bouncing off the surface. This introduces issues like glare, texture, and uneven surfaces. Lighting becomes critical, typically with two lights positioned at 45° to ensure even coverage.
• Transmissive materials (negatives, slides) flip the process entirely. Light passes through the object, revealing detail embedded within the material itself. As discussed, this requires much higher resolution and careful handling of dynamic range to capture shadow and highlight detail .

It’s not just a technical difference; it’s a completely different mindset. 

Colour: Where Things Get Serious

If there was one moment where the room collectively leaned in, it was during the discussion of colour accuracy.

Colour in digitisation isn’t subjective - it’s measured. Using ΔE (Delta E), practitioners can quantify how close a captured colour is to a known reference. A value under 2 is invisible to the human eye, while anything above 5 becomes clearly inaccurate.

This ties directly into calibration. Every device, camera, monitor, scanner, has its own “opinion” about colour. Without calibration, those opinions clash. The presentation made it clear: calibration isn’t optional; it’s foundational. 

Resolution Isn’t Just Megapixels

 Another myth the talk dismantled was the idea that higher megapixels automatically mean better results.

The reality is far more nuanced. Resolution requirements depend on the object. A 35mm negative might require around 21 megapixels for archival standards, while large-format materials can demand hundreds of megapixels or even stitched captures.

Then there’s bit depth - something rarely discussed outside professional workflows. Moving from 8-bit to 16-bit capture dramatically increases the amount of colour and tonal information recorded, enabling smoother gradients and more accurate reproductions.

In short, it’s not just how many pixels you have, it’s how much information each pixel carries. 

The Gear (and Why It Matters)

• Lenses must be flat-field and distortion-free
• Copy stands must be rigid and perfectly aligned.
• Lighting must be even, colour-correct, and consistent.

The images shown in the presentation (particularly the equipment sections) reinforced how engineered these setups are. Every component exists to remove variables and increase repeatability. 

More Than Capture: The Workflow

Beyond capture, the talk also touched on file formats and long-term preservation. Open formats like DNG were highlighted as future-proof solutions, ensuring compatibility and preserving metadata over time.

And then there are the everyday challenges: dust, movement, lighting inconsistencies, and data management. Digitisation isn’t a one-click process - it’s a discipline.  

Why It Matters

What made the presentation resonate wasn’t just the technical depth; it was the purpose behind it.

Digitisation is about access, preservation, and trust. When done correctly, it allows fragile, rare, or inaccessible objects to be studied and shared without risking damage to the original. But that only works if the digital version is a faithful surrogate.

That’s the real takeaway from the session: Heritage digitisation isn’t about creating images - it’s about creating evidence.