Understanding Contrast Ratios & LRV for Dementia-Friendly Design
Light Reflectance Value (LRV) is the objective measure behind dementia-friendly contrast. This technical guide explains how LRV is measured, what contrast ratios the DSDC recommends, how to calculate LRV differences, and how to verify contrast performance in your care home.
Contrast is the foundation of visibility in dementia-friendly design. Without sufficient contrast between a sign and its surroundings, and between the elements within a sign, the most carefully designed wayfinding system is invisible to the residents it serves. Light Reflectance Value (LRV) provides an objective, measurable framework for specifying contrast. This guide explains the science behind LRV, the standards that apply, and how to verify contrast performance in practice.
What Is Light Reflectance Value?#
LRV measures the percentage of visible light reflected by a surface, expressed on a scale from 0 (absolute black, absorbs all light) to 100 (perfect white, reflects all light). In practice, the darkest common building materials have an LRV of around 5-10, and the lightest around 85-90. LRV is measured using a spectrophotometer under standardised illumination conditions. Paint manufacturers typically publish LRV data for their products, and signage suppliers should provide LRV values for their sign faces and frames. LRV is independent of colour hue -- a dark blue and a dark green can have very similar LRVs despite appearing as different colours.
DSDC Contrast Requirements#
The DSDC recommends a minimum LRV difference of 30 points between critical adjacent surfaces. This applies to three contrast relationships in signage: the sign face against the wall (ensuring the sign is visible as an object), the text/imagery against the sign background (ensuring the content is readable), and the sign frame against both the sign face and the wall. An LRV difference of 40+ points is considered excellent and provides a significant safety margin for residents with advanced dementia and severe contrast sensitivity loss.
Practical LRV contrast examples:
- White acrylic sign (LRV ~85) on a mid-blue wall (LRV ~35) = 50-point difference (excellent)
- White acrylic sign (LRV ~85) on a cream wall (LRV ~75) = 10-point difference (insufficient)
- Dark oak frame (LRV ~20) on a cream wall (LRV ~75) = 55-point difference (excellent)
- Mid-grey sign (LRV ~45) on a pale grey wall (LRV ~60) = 15-point difference (insufficient)
- Dark text (LRV ~10) on white sign face (LRV ~85) = 75-point difference (excellent)
- BS 8300:2018 specifies a minimum 30-point LRV difference for critical visual information in accessible buildings
Measuring and Verifying LRV#
For precise LRV measurement, a handheld spectrophotometer provides reliable readings. However, for practical purposes, paint manufacturers publish LRV values in their product specifications, and sign suppliers should provide LRV data on request. When specifying wall colours for areas where signs will be mounted, select a paint colour with a published LRV that provides at least a 30-point difference from the sign face LRV. If exact LRV data is unavailable, the 'monochrome photograph test' offers a rough guide: photograph the sign on the wall in black and white, and if the sign boundary is clearly distinguishable, contrast is likely adequate.
Pro Tip
Request the LRV specification for your wall paint from the manufacturer before ordering signage. This allows your sign supplier to recommend the optimal sign colour for maximum contrast. Getting this right at the specification stage prevents costly repainting or sign replacement later.
BS 8300
2018 Section 9.2.1 states that visual contrast between critical surfaces should have a minimum difference of 30 points on the LRV scale. This is a Building Regulation benchmark, not merely a best practice recommendation, and applies to signage in accessible buildings including care homes.
"Contrast is not about choosing colours that look different to you. It is about measuring whether the Light Reflectance Values provide sufficient difference for someone whose visual processing is significantly impaired." -- DSDC Design Guidance
Recommended Products
Every sign colour in our range is published with its LRV data, enabling precise contrast calculations against your specific wall colours. Our white acrylic base (LRV ~85) provides excellent contrast against the majority of wall finishes used in care homes.
LRV is the language of contrast in accessible and dementia-friendly design. By understanding and applying LRV-based contrast specifications, care homes can move beyond subjective colour judgements and ensure that every sign in their building is genuinely visible to every resident.
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