Neutral Density Gel

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Gray gel filter that reduces light intensity without affecting color temperature; commonly used on luminaires or windows in cinematography.

Overview

A Neutral Density Gel (ND Gel, also known as "gray filter foil" or "neutral density foil" in German) is a transparent, neutral gray filter foil used in film and TV lighting to reduce the amount of light. Unlike color gels or conversion gels (CTO/CTB), an ND gel ideally only affects the brightness and leaves the color temperature of the light unchanged ("neutral"). It is placed in front of lights (in filter holders, on barndoors) or applied as a film to window panes to bring bright daylight from outside down to the level of the interior lighting.

ND gels should be distinguished from ND filters placed in front of the camera lens (glass or resin filters): the gel is at the light source or window and controls the light in the scene, while the camera filter controls the exposure at the sensor.

Density and Stops

The strength is indicated by optical density. For every 0.3 density units, the light transmission is halved, which corresponds to a reduction of one f-stop. The most common gradations:

Density	Reduction	Transmission (approx.)	LEE No.	Rosco Cinegel
ND 0.3 (N.3)	1 Stop	~50 %	209	3402 (N.3)
ND 0.6 (N.6)	2 Stops	~25 %	210	3403 (N.6)
ND 0.9 (N.9)	3 Stops	~12 %	211	3404 (N.9)

Multiple layers can be combined to add densities (e.g., two ND 0.6 gels result in approximately 4 stops of reduction).

Technical Data

Material: Deep-dyed, heat-resistant polyester, for stable light transmission and color fidelity.
Forms: Individual sheets (typical sheet size around 53 × 122 cm) and rolls (common roll widths are about 1.22 m).
Handling: Can be cut freely with scissors or a cutter; can be attached to the light source in filter frames, behind barndoors, or with clips.
Key Manufacturers/Brands: LEE Filters (Series 209/210/211), Rosco (Cinegel Series 3402/3403/3404 and E-Colour+ 209/210/211).

On-Set Use

Typical applications include darkening overly bright windows so that exterior and interior light fall within a common exposure range (window patches), as well as reducing the output of individual lights without altering their color or dimming them electrically (dimming would lower the color temperature of incandescent lamps). If the gel is used directly on a hot light, ensure sufficient distance and ventilation; with very high-power lights, the foil can be subjected to thermal stress. For daylight windows, there are also self-adhesive ND window films as a related product group.

From the crafts

Perspectives

Cinematographer

Aus DoP-Perspektive ist dieses Element essentiell für die visuelle Gestaltung. Es ermöglicht mir die gewünschte Farbstimmung und das ästhetische Bild konsistent umzusetzen.

Producer

Diese professionelle Lösung erhöht die Produktionseffizienz und reduziert Post-Production-Anforderungen. Sie ermöglicht flexible, schnelle Anpassungen während des Drehs.

Gaffer

Als Gaffer ist dies ein unverzichtbares Werkzeug meines täglichen Handwerkszeugs. Es ermöglicht mir professionelle Lichtkontrolle und schnelle Anpassungen auf Set, was Zeit spart und Qualität sichert.