What to monitor
Start with the variables that actually explain the risk.
For this material group, the environmental record is most useful when it captures the things below and keeps them tied to the object, space or display context.
- Relative humidity and stability
- Temperature, especially for chemically unstable processes
- Visible light and cumulative exposure
- UV in display areas
- Storage type and process identification
What can go wrong
The number only matters because of the damage mechanism behind it.
Chemical ageing
Higher temperature can accelerate fading, tarnishing and other chemical reactions. Some film bases and colour processes benefit from specialist cool or cold storage.
Moisture sensitivity
Damp conditions can encourage mould and sticking, while very dry conditions can increase brittleness. Rapid swings are particularly unhelpful.
Light sensitivity
Old and coloured photographs are commonly treated as very light sensitive. Process, colourants and previous exposure all affect the real risk.
Published guidance
Useful examples, with the caveat kept attached.
Museums Galleries Scotland gives 30–45% RH as a broad example for photographs and films. Icon advises a stable environment and, where possible, 30–40% RH for photographs. MGS places coloured and old photographs in its 50 lux group, while modern black and white photographs sit in the 200 lux group. The National Archives notes that film and photographic archives can need specialist storage beyond ordinary archive conditions.
Where judgement comes in
Do not use one “photography” profile for a mixed photographic collection unless a specialist has confirmed that it is appropriate. Glass plate negatives, colour prints, acetate film, nitrate film and modern black and white material can have very different preservation needs and hazards.
How this maps to LÆFAN
Keep the reason for the profile with the readings.
Separate specialist photographic stores from general paper/archive profiles when their environment is different.
Track temperature as well as RH, because temperature can be particularly important to chemical ageing.
Use light budgets for displayed photographs rather than only instantaneous lux limits.
Record process or collection type in the profile notes so the reason for the environmental choice is not lost.
LÆFAN does not decide the conservation limit for you. It records the profile your institution has chosen, the source or rationale behind it, where it applies and what happened while it was in force.
Sources & further reading
Where the examples on this page came from.
Temperature and humidity in museums
Open source ↗Conservation and lighting
Open source ↗How to care for your photographs
Open source ↗Preservation guidance for archives
Open source ↗Sources checked 6 October 2026. Guidance and standards can change, so follow the linked publisher page before adopting a value into policy.