CTO-025 Color Temperature Orange (Warming) Filter
3/4 CTO colour-conversion filter shifting 5600 K toward 3400 K for seamless mixed-lighting balance in broadcast, film, and architectural applications.
- Colour shift direction: Warming (5600 K → 3400 K)
- Mired shift: +100 Mired
- Correction strength: 3/4 CTO
- Average transmittance: ~50.6 % T (visible range)
- Peak transmittance: ~93.3 % T near 780 nm
- Minimum transmittance: ~10.6 % T near 437 nm
- Construction: Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick
- Custom options: Intermediate Mired shifts, combined CTO+diffusion, custom sizes, rapid prototypes
Learn more
CTO-025 delivers a +100 Mired shift to move 5600 K light toward 3400 K. Its smooth spectral slope creates a natural warming effect, with about 50.6 % average visible transmittance and a low amount of light loss.
The ion-assisted hard-oxide coating is built for repeated handling, heat, and cleaning.
Best suited for:
Strong but not full warming when you want a natural blend between daylight and tungsten sources.
Description
CTO-025 is the deepest-cutting filter in the CTO range, with its 50 % crossover at 657 nm - well into the red region. Everything below this point is heavily suppressed: violet averages 13.5 %, blue 12.1 %, green just 7.7 %, and even yellow and orange stay below 15 %. Only the red band breaks through, climbing from 50 % at the crossover to an average of 93.6 % in the NIR (700-800 nm), peaking at 95.5 % at 687 nm. The result is an extremely narrow warm transmission that isolates deep red and NIR while rejecting virtually the entire visible spectrum below 650 nm.
Key Advantages
- 50 % crossover at 657 nm (deep red) - isolates the red and NIR bands with near-complete rejection of all shorter visible wavelengths.
- Peak transmission of 95.5 % at 687 nm - delivers high throughput in the deep-red window critical for many sensing applications.
- Broad visible blocking (blue avg 12 %, green avg 7.7 %) - approaches the performance of a dedicated deep-red longpass filter.
- Hard-oxide durability - ion-assisted coating survives high lamp temperatures, humidity, solvents, and repeated cleaning.
- Custom formats available - round, square, or free-form blanks from 5 mm to 450 mm, thickness 0.21-3.8 mm, on Borofloat®, soda-lime, Schott D263 T, or Corning Eagle XG substrates.
Typical Applications
- Stage and concert lighting - produces deeply saturated red washes and dramatic fire-effect lighting with virtually no colour contamination.
- Darkroom and safelight filtration - passes only deep red and NIR wavelengths, providing safe illumination for photosensitive materials.
- NIR-enhanced imaging - functions as a deep-red longpass filter for machine vision and surveillance cameras that benefit from NIR sensitivity.
- Horticulture and photobiology - isolates the deep-red photosynthetically active radiation (PAR) peak at 660 nm for targeted plant-growth studies.
- Biomedical and fluorescence imaging - passes Cy5 and similar deep-red fluorophore emissions while blocking excitation wavelengths below 650 nm.
Need prototypes in days or production volumes next quarter? CTO-025 filters can be coated, diced, and shipped to your exact specifications.
FAQ
CTO-025 FAQ
What is CTO-025 and what is it used for?
CTO-025 is a Color Temperature Orange Filter - Extreme Deep Red (T50 % = 656 nm). CTO-025 is the deepest-cutting filter in the CTO range, with its 50 % crossover at 657 nm - well into the red region. Everything below this point is heavily suppressed: violet averages 13.5 %, blue 12.1 %, green just 7.7 %, and even yellow and orange stay below 15 %. Common uses include Stage and concert lighting, Darkroom and safelight filtration, NIR-enhanced imaging, and Horticulture and photobiology.
What are the key optical specs of CTO-025?
Key published specs for CTO-025 include Colour shift direction: Warming (5600 K → 3400 K); Mired shift: +100 Mired; Correction strength: 3/4 CTO; Average transmittance: ~50.6 % T (visible range); Peak transmittance: ~93.3 % T near 780 nm.
What applications is CTO-025 best suited for?
CTO-025 is commonly used for Stage and concert lighting, Darkroom and safelight filtration, NIR-enhanced imaging, and Horticulture and photobiology. Stage and concert lighting - produces deeply saturated red washes and dramatic fire-effect lighting with virtually no colour contamination.
Can CTO-025 be customized for size, substrate, or coating requirements?
KUPO lists the construction for CTO-025 as Ion-assisted hard-oxide; 5 – 450 mm shapes, 0.21 – 3.8 mm thick. Published custom options include Intermediate Mired shifts, combined CTO+diffusion, custom sizes, rapid prototypes. Custom formats available - round, square, or free-form blanks from 5 mm to 450 mm, thickness 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 CTO-025?
The ion-assisted hard-oxide coating is built for repeated handling, heat, and cleaning.
