CTO-021 is a Color Temperature Filter designed to add a controlled warming shift while keeping the spectrum smooth and predictable. It gently reduces blue energy relative to the longer wavelengths, then rises progressively through the visible range, allowing reds and ambers to pass more freely. This produces a natural-looking warm balance change that helps lighting and camera systems move toward a warmer white point without introducing harsh spectral cutoffs.
Key advantages
Controlled warming shift – moves correlated color temperature warmer by reducing blue content relative to red and amber.
Smooth spectral response – avoids sharp transitions that can cause banding, unnatural hues, or channel artifacts.
Strong long-wavelength throughput – preserves reds and ambers for healthier skin tones and richer warm highlights.
Stable, repeatable tuning – consistent performance supports matching across fixtures and production batches.
Hard-oxide durability – ion-assisted coating options resist heat, humidity, solvents, and repeated cleaning.
Flexible formats (KUPO custom-made optical filters) – round, square, or complex blanks from 5 mm to 450 mm, 0.21–3.8 mm thick, on Borofloat®, soda-lime, Schott D263 T, or Corning Eagle XG glass.
Typical applications
Stage and architectural lighting – warm LED or discharge sources toward a tungsten-like feel while keeping output smooth.
Broadcast and studio fixtures – tune correlated color temperature to match cameras, sets, or mixed lighting environments.
Film and photography – warm key or fill lights for flattering tones and consistent white balance.
Retail and exhibition lighting – enhance warm materials such as wood, textiles, and food displays while maintaining a natural look.
Optical systems needing warming – introduce controlled warmth without harsh spectral discontinuities.
Need prototypes fast or production volumes soon? CTO-021 filters can be coated, diced, and shipped to your exact specifications quickly, and because KUPO can custom-make optical filters, we can tune warming strength, substrate, thickness, and angle-of-incidence targets to match your light source and optical stack.