CRI-4 Color Rendering Improvement Filter
Colour-rendering enhancement filter boosting CRI from typical LED and fluorescent sources to deliver richer, more natural colour reproduction for retail, broadcast, and architectural lighting.
- Colorimetric performance
- Target source type: Phosphor-converted white LED / fluorescent
- CRI Ra improvement: 75 → 92+ (typical)
- R9 (deep red) improvement: 10–30 → 80+ (typical)
- Colour temperature shift: Minimal (< 200 K shift typical)
- Light output reduction: ~23.3 %
- Spectral characteristics
- Spectral method: Selective suppression of excess yellow-green emission
- Key modification region: 380 – 608 nm
- Average transmittance: ~76.7 % T (visible range)
- Construction: Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick
- Custom options: Source-specific tuning, combined CRI + colour temperature correction, rapid prototypes
Learn more
CRI-4 CRI delivers Target source type Phosphor-converted white LED / fluorescent, CRI Ra improvement 75 → 92+ (typical), and R9 (deep red) improvement 10–30 → 80+ (typical).
The hard-oxide coating is built for repeated handling, heat, and cleaning.
Best suited for:
Retail environments upgrading mid-grade LED fixtures to high-CRI performance for improved merchandise colour presentation — particularly effective over cosmetics, fresh food, and fashion displays where subtle colour differences matter to shoppers
Description
CRI-4 targets the exact spectral problem created by phosphor-converted LEDs: excess yellow-green output that flattens perceived contrast and desaturates warm tones. By suppressing the 500-560 nm yellow-green band to a minimum of 30.1 % at 523 nm, CRI-4 restores natural colour discrimination without the heavy transmission loss of broadband warm filters. The 65.1 % average transmission and 85 %+ red passband mean skin tones appear more natural, foliage more authentic, and warm highlights genuinely incandescent.
Key Advantages
- Deep Yellow-Green Notch (30.1 % at 523 nm) - Precisely suppresses the phosphor-LED yellow-green spike responsible for flat, de-saturated colour rendering in LED stage and architectural fixtures.
- Red-Channel Preservation (85 %+) - Full red passband maintains warm highlight reproduction; human skin, wood, and natural materials regain perceptual depth lost under unfiltered LED sources.
- Balanced Average Transmission (65.1 %) - Achieves meaningful colour correction without the output penalty of heavy warm filters; suitable for high-lumen LED arrays requiring efficiency.
- Hard-Oxide Ion-Assisted Coating - Resists delamination, UV degradation, and thermal cycling from continuous LED output; maintains spectral performance across thousands of fixture hours.
- Custom Format Availability - Supplied as 25-450 mm rounds, squares, or free-form blanks in Borofloat, soda-lime, D263 T, or Eagle XG at 0.21-3.8 mm thickness for direct fixture integration.
Typical Applications
- LED Stage Wash Lighting - Corrects yellow-green LED fringing that washes out costume and skin-tone saturation; warm highlight reproduction is restored without supplementary warm-white fixtures.
- Television Studio Lighting - Eliminates the yellow-green artefact that degrades skin tones under LED key lighting in HD and 4K broadcast environments.
- Museum and Gallery Lighting - Suppresses the yellow-green component of LED track lighting to present oil paintings, textiles, and ceramics with authentic warm-highlight depth.
- Hospitality Interior Lighting - Corrects the flat, artificial appearance of LED downlights and wall-wash fixtures in hotels, restaurants, and retail environments where perceived warmth drives guest experience.
- Architectural LED Upgrade Projects - Enables drop-in CRI correction for existing LED luminaire upgrades without redesigning optical systems or replacing entire fixture arrays.
CRI-4 samples available in 3-4 weeks; production quantities deliver on schedule with custom OEM integration support available from initial prototype through volume ramp.
FAQ
CRI-4 FAQ
What is CRI-4 and what is it used for?
CRI-4 is a Surgical Yellow-Green Notch Correction. CRI-4 targets the exact spectral problem created by phosphor-converted LEDs: excess green around 565 nm. With peak transmission at 95.9 % at 694 nm and a sharp notch dropping to 33.7 % at 565 nm, this filter preserves UV (81.0 %), blue (69.1 %), and red (90.0 %) while excising the problematic yellow-green peak. Common uses include Medical Surgical Suites, Machine Vision & Quality Inspection, High-End Jewelry & Gemstone Retail, and Broadcast & Studio Video Production.
What are the key optical specs of CRI-4?
Key published specs for CRI-4 include Target source type: Phosphor-converted white LED / fluorescent; CRI Ra improvement: 75 → 92+ (typical); R9 (deep red) improvement: 10–30 → 80+ (typical); Colour temperature shift: Minimal (< 200 K shift typical); Light output reduction: ~23.3 %.
What applications is CRI-4 best suited for?
CRI-4 is commonly used for Medical Surgical Suites, Machine Vision & Quality Inspection, High-End Jewelry & Gemstone Retail, and Broadcast & Studio Video Production. Medical Surgical Suites - Operating room lighting achieves CRI > 95 with zero color-shift from the source; tissue color discrimination remains optimal throughout multi-hour procedures without perceptual fatigue.
Can CRI-4 be customized for size, substrate, or coating requirements?
KUPO lists the construction for CRI-4 as Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick. Published custom options include Source-specific tuning, combined CRI + colour temperature correction, rapid prototypes. Modular Optical Integration - Available in round 5-450 mm, square, and custom-cut blanks on Borofloat, D263 T, soda-lime, and Eagle XG with 0.21-3.8 mm substrate thickness for retrofit and new-build fixtures.
What should I know about angle of incidence and durability for CRI-4?
The hard-oxide coating is built for repeated handling, heat, and cleaning.
