R3409 Roscosun 1/4 CTO — a gentle daylight-to-warm correction
Converts 5500K to 4500K with 81% transmission. Use it to warm daylight sources slightly, or for a subtle correction when full or half CTO is too much.
Image: Rosco
Small, controlled warming
Roscosun 1/4 CTO shifts daylight-balanced sources a quarter of the way towards tungsten. It’s the finer step in the Roscosun series between 1/8 and 1/2 CTO.
- Converts 5500K to 4500K
- Transmission 81% (per Rosco)
- Warms HMI, daylight LED and window light
- Fine-tunes mixed sources
- Stackable with other CTO grades
- Optically clear correction filter
Film, TV, photography — and stage
Matching sources
Nudge daylight fixtures toward warmer practicals or ambient light.
Skin tones
A subtle warm-up on daylight keys and fills.
Windows
Taking the edge off cool daylight when cut for frames or windows (rolls).
What it is — and what it isn’t
Use it for
- Slight warming of daylight sources
- Matching mixed colour temperatures
- Fine-tuning between 1/8 and 1/2 CTO
- Warming daylight LED and HMI fixtures
Don’t use it for
- Full daylight-to-tungsten conversion — use R3407 Full CTO
- Cooling a source — use a CTB
- Diffusing or softening light
- Placing directly against hot lamps
Getting the best result
- Measure or judge the colour temperature you need to match.
- Cut the filter to the frame or holder size.
- Mount it clear of the lamp with airflow.
- Check on camera; stack or step up/down a grade if needed.
- Replace if it fades or heat-distorts.
Key details
| Range | Rosco Cinegel — Roscosun |
|---|---|
| Filter | R3409 Roscosun 1/4 CTO |
| Conversion (per Rosco) | 5500K to 4500K |
| Transmission (per Rosco) | 81% |
| Base (Cinegel polyester, per Rosco) | Polyester (PET), 1.4–2.5 mil (35–64 µm) nominal |
| Heat (Cinegel polyester, per Rosco) | Softens at 126°C; melts at 143°C |
| Standard Rosco formats | Sheet 20" × 24" (50 × 60 cm); roll 48" × 25' (1.2 × 7.62 m) |
| Sizes | As listed above |
Common questions
What does 1/4 CTO do?
Rosco R3409 converts 5500K daylight to 4500K — a gentle warming correction.
How much light does it lose?
Rosco lists transmission at 81%.
1/4 CTO vs 1/2 CTO?
R3408 Roscosun 1/2 CTO converts 5500K to 3800K (73% transmission) — a bigger shift. 1/4 is for subtler correction.
Can I stack CTO filters?
Yes, stacking adds correction. Check the result on camera or with a meter.
Is it suitable for LED fixtures?
Yes — it corrects any daylight-balanced source. Always check on camera.
Filter specifications are from Rosco published data and are a guide only. Results depend on the fixture, lamp, distance and camera — always test with your own rig before the job. Keep filters clear of hot lamps and allow airflow; heat and UV shorten filter life. Figures and advice on this page are a guide only.
Need help choosing?
Tell us what you’re working on and we’ll point you to the right product for the job.
Available Sizes (Reference)
| Format | Imperial Size | Metric Size |
|---|---|---|
| Standard Sheet | 20 in × 24 in | 508 mm × 610 mm |
| Standard Roll | 48 in × 25 ft | 1.22 m × 7.62 m |
| Wide Roll (selected materials) | 60 in × 20 ft | 1.52 m × 6.10 m |
Exact availability varies depending on the Cinegel material and colour.
Rosco Cinegel Lighting Filters
Rosco Cinegel is a professional range of lighting filters used in film, television, photography and video to colour, correct, diffuse and control light.
Cinegel is especially popular for studio lighting, location shoots, overhead frames, butterflies and grip setups where cinematographers need reliable tools to shape and modify light.
- Wide range of correction, diffusion and effects materials
- Designed for cinematography and professional lighting
- Used worldwide in film, TV and photography
- Trusted by gaffers and lighting technicians
What Cinegel is used for
- Colour correction for tungsten, daylight and mixed lighting
- Diffusion and softening of lighting fixtures
- Neutral density and exposure control
- Camera colour calibration (CalColor system)
- Lighting control in film, TV and photography
- Butterflies, overhead frames and large lighting setups
Want to Test Filters Before Ordering Full Sheets?
If you'd like to compare Cinegel materials before committing to larger sheets or rolls, Rosco offers compact reference products commonly used by cinematographers and lighting technicians.
-
Cinegel Swatchbook – a compact reference with real Cinegel samples for previewing colour correction, diffusion and effects filters.
View the Cinegel Swatchbook -
Cinegel Sampler Kit – a curated selection of commonly used Cinegel materials for hands-on testing with lighting fixtures.
View the Cinegel Sampler Kit -
Colour Correction Kit – a practical tester kit containing commonly used colour correction filters such as CTO, CTB and other correction materials.
View the Colour Correction Kit
Learn More About Colour Correction Filters
If you’re unsure which colour correction filter to use, our guide explains the differences between CTO, CTB, colour temperature correction and other commonly used lighting filters.
Protection for High Heat Fixtures
Lighting filters installed in high-output fixtures may degrade faster when exposed to excessive heat.
Use Rosco Super Heatshield 1991 where additional heat protection is required to extend filter life.
UV Protection for Lighting Filters
Lighting filters exposed to ultraviolet light sources or prolonged UV exposure may fade or degrade over time.
For filters exposed to UV sources, consider adding R3114 Tough UV Filter to provide additional protection.
Installation Tips
- Install filters securely using clips, frames or holders.
- Avoid placing filters directly against hot lamps.
- Allow airflow around lighting fixtures where possible.
- Replace filters if colour shift, heat damage or warping becomes visible.
Cautions & Disclaimer
- Lighting filters may degrade over time depending on heat, fixture type and light intensity.
- Always monitor filters installed in high-output fixtures.
- Use appropriate heat or UV protection where necessary.
All technical data, recommendations and service are accurate to the best of our knowledge. Rosco assumes no responsibility for results obtained or damage incurred from use since method of application and use are beyond our control.
