HMG-4 Minus Green Filter
HMG-4 is a magenta-balance (minus-green) broadband filter that cleans yellow-green casts from LED/fluorescent sources while preserving healthy blue and strong long-red for neutral whites and natural skin tones.
- Function: Minus-green correction; trims yellow-green while keeping blue & long-red
- Balanced blue: ~64–66 % T (390–410 nm) rising to ~75–78 % near 455–470 nm
- Green moderation: Controlled dip ~62–64 % around 540–550 nm (neutralizes “plus-green”)
- Long-red richness: ~88–91 % T around 650–665 nm; tapered ~50 % by ~780 nm
- Smooth profile: Low-ripple, gently shaped curve for predictable, non-banded corrections
- Construction & format: Durable dielectric on Borofloat®, Eagle XG, D263 T, or soda-lime • 5–450 mm • 0.21–3.8 mm • options: rear-AR & slight wedge
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HMG-4 removes greenish ambience without pushing scenes too magenta, maintaining crisp whites and warm, natural reds. The smooth spectral shaping stays consistent across fixtures and dim levels.
Typical applications • Cinema/TV lighting (lift TLCI/CRI by pulling excess green) • Photography & events (cleaner skin tones under mixed LED/fluoro) • Retail/museum/hospitality (true product/art colour) • Architectural & display (warmer, premium ambience) • Machine vision (reduce green flare; stabilize red-dominant features).
Need test chips tomorrow or thousands next quarter? HMG-4 filters are coated and cut-to-size (including dicing) to your exact spec—fast.
Description
HMG-4 delivers moderate minus green suppression with a measured approach to color correction. This half minus green filter reduces spectral output in the 510-580 nm range to approximately 66 % average while maintaining strong red transmission at 84.9 % and sustained blue passage at 70.9 %. The filter achieves a gentle dip in the green spectrum without sacrificing overall system transmission, making it ideal for applications requiring mild to moderate fluorescent source correction. Peak transmission of 90.5 % at 652 nm provides excellent efficiency across the visible spectrum.
Key Advantages
- Moderate Green Suppression - Reduces green output by ~33 % while preserving > 85 % red transmission and > 70 % blue, offering balanced correction without over-correction artifacts
- Flat Visible Spectrum Response - Gentle correction curve minimizes color casting, delivering natural color balance when correcting mild to moderate green-dominant sources like standard fluorescent panels
- Broad Compatibility - Works effectively with tungsten, HMI, fluorescent, and newer LED sources exhibiting moderate green excess, making it versatile for mixed-lighting environments
- Hard-Oxide Ion-Assisted Coating - Durable multi-layer dichroic structure resists scratching, abrasion, and thermal cycling - essential for demanding field and studio use with repeated handling
- Custom Format Options - Available in round, square, free-form blanks from 5 mm to 450 mm diameter in thicknesses of 0.21-3.8 mm on Borofloat, soda-lime, Schott D263 T, or Corning Eagle XG substrates
Typical Applications
- Stage & Theater Lighting - Correct tungsten-HMI hybrid rigs where fluorescent work lights introduce unwanted green casts affecting actor skin tones and scenic color fidelity
- Documentary & ENG Production - Balance mixed indoor-outdoor shoots combining daylight, tungsten fill, and ambient fluorescent sources in office and institutional environments
- Broadcast & Studio News - Compensate for standard fluorescent ceiling grids and economical LED panel arrays commonly found in news studios and interview sets
- Machine Vision Inspection - Achieve neutral white balance in factory lighting conditions where mercury vapor or older T8 fluorescent arrays create systematic green bias in captured images
- Event & Live Sound Production - Stabilize color consistency during concerts and conferences where venue lighting mixes tungsten spotlights with energy-efficient green-heavy LED washes
Request samples for rapid prototyping on your specific lighting rig. HMG-4 supports volume production with flexible coating specifications.
FAQ
HMG-4 FAQ
What is HMG-4 and what is it used for?
HMG-4 is a Balanced Minus Green Correction. HMG-4 delivers moderate minus green suppression with a measured approach to color correction. This half minus green filter reduces spectral output in the 510-580 nm range to approximately 66 % average while maintaining strong red transmission at 84.9 % and sustained blue passage at 70.9 %. Common uses include Stage & Theater Lighting, Documentary & ENG Production, Broadcast & Studio News, and Machine Vision Inspection.
What are the key optical specs of HMG-4?
Key published specs for HMG-4 include Correction strength: 1/4 Minus Green; Green rejection band: ~513 – 581 nm; Peak suppression: ~62.7 % T near 547 nm; Blue passband: ~71.4 % T (400 – 490 nm); Red passband: ~84.9 % T (600 – 700 nm).
What applications is HMG-4 best suited for?
HMG-4 is commonly used for Stage & Theater Lighting, Documentary & ENG Production, Broadcast & Studio News, and Machine Vision Inspection. Stage & Theater Lighting - Correct tungsten-HMI hybrid rigs where fluorescent work lights introduce unwanted green casts affecting actor skin tones and scenic color fidelity.
Can HMG-4 be customized for size, substrate, or coating requirements?
KUPO lists the construction for HMG-4 as Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick. Published custom options include Intermediate correction strengths, combined Minus Green + CTO/CTB, rapid prototypes. Custom Format Options - Available in round, square, free-form blanks from 5 mm to 450 mm diameter in thicknesses of 0.21-3.8 mm on Borofloat, soda-lime, Schott D263 T, or Corning Eagle XG substrates.
What should I know about angle of incidence and durability for HMG-4?
The hard-oxide coating is built for repeated handling, heat, and cleaning.
