CRI-28 Color Rendering Improvement Filter

CRI-28 is a colour-rendering improvement (CRI) filter that warms and smooths spiky LED/HMI spectra by suppressing deep blue and broad yellow-green while preserving a cyan window and strong long-red. Transmission sits high in the near-UV/blue (~88–90% at ~390–410 nm), drops into a deep blue notch near ~450–460 nm (~13–16% T), surges to a narrow cyan peak of ~90–92% around ~490–505 nm, then falls into a broad trough across ~520–620 nm with a minimum of ~15–20% near ~570–585 nm. It climbs steeply through the red to ~92–94% by ~690–760+ nm with low ripple.

Key advantages

• Raise CRI/TLCI and R9 — moderates the ~450 nm spike and the ~520–620 nm band while keeping strong long-red for natural skin, wood, food, and fabrics.

• Dual-notch, dual-pass profile — deep attenuation at ~450 nm and ~570–585 nm with high throughput in cyan (~490–505 nm) and long-red (>~690 nm).

• Colour-temperature tuning — shifts overly cool sources toward neutral/warm without magenta/green casts.

• Predictable shaping — smooth slopes and broad features avoid banding and preserve colour balance.

• Built for production — durable dielectric stack for sets, stages, and architectural fixtures; optional rear-surface AR and slight wedge to suppress ghosts.

• Custom formats — Borofloat®, Eagle XG, or D263 T (0.21–3.8 mm) for high-temp duty to ~450 °C; soda-lime for ≤150 °C. Sizes 5–450 mm.

Typical applications

• Cinema/TV lighting — lift TLCI/CRI and skin-tone accuracy with less in-camera correction.

• Photography & events — warmer, more flattering faces and textiles under LED or HMI.

• Retail, museum & hospitality — reduce green cast and reveal natural reds in merchandise and art.

• Architectural & display — refine off-the-shelf luminaires for premium colour.

• Machine vision — balance channels where red features matter and blue/green glare is problematic.

Need test chips tomorrow or thousands next quarter? CRI-28 filters are coated and cut-to-size (including dicing) to your exact spec—fast.