The Complete Guide to LEE Filters Lighting Gels

Last updated: 7 August 2026. Prices are in AUD and correct at the time of writing, check the linked product pages for live pricing and stock.

LEE Filters lighting gels are the coloured and diffusing sheets you put in front of a light to change its colour, temperature, softness or brightness. They're a cornerstone of film, TV and theatre lighting. This guide explains the four jobs gels do, colour correction, colour effect, diffusion and neutral density, plus the numbering system and the swatch book. For practical recipes, see our how to use LEE Filters guide.

The four jobs a gel does

Colour correction: CTB, CTO and CT Straw

Correction gels make mismatched sources agree. CTO (Colour Temperature Orange) warms a daylight source down toward tungsten, Full CTO shifts roughly 5,600K daylight to about 3,200K, while CTB (Colour Temperature Blue) cools a tungsten source up toward daylight (Full CTB). Both come in graded strengths, full, half, quarter and eighth, so you can nudge colour temperature by just the amount you need. CT Straw adds warm, sunny straw tones.

Green correction: Plus and Minus Green

Some fluorescent and older LED sources have a green spike. Minus Green (magenta) gels like the Quarter Minus Green cancel it, while Plus Green (like Half Plus Green) pushes a source green to match existing fluorescents, essential for matching mixed practical lighting.

Colour effect gels

The big palette of creative colour, Primary Red, Just Blue, Bastard Amber and hundreds more, for mood, backgrounds and stylised looks. Each has a LEE number you can specify exactly and repeat across a shoot.

Diffusion

Diffusion softens a hard source and spreads it. The White Diffusion family steps through strengths, Full (216), Half (250), Quarter (251) and Eighth (252), while frosts like Hampshire Frost, Heavy Frost and Opal Frost give different softening characters. For big, even soft sources there's Light Grid Cloth and the Quiet Light Grid.

Neutral density (ND)

ND cuts brightness without changing colour, perfect for balancing a bright window to interior levels, or knocking a light down without re-rigging. Strengths are given in density: .3 (one stop), .6 (two stops), .9 (three stops) and 1.2 (four stops).

Technical: black foil and heat shield

Black Foil (280) is matte-black aluminium foil for flagging light, blocking spill and making quick masks, an on-set staple. Heat Shield (269) reflects heat away from gels and gear near hot fixtures.

The swatch book and numbering

Every LEE gel has a number, and the LEE Swatch Book holds a physical sample of each so you can hold colours up to a light and specify exactly what you want. It's the cheapest, most useful thing in any lighting kit. Gels are sold as sheets, with rolls available for bigger jobs.

Frequently asked questions

What is the difference between CTB and CTO gels?

CTO (Colour Temperature Orange) warms a daylight-balanced source down toward tungsten; CTB (Colour Temperature Blue) cools a tungsten source up toward daylight. Both come in full, half, quarter and eighth strengths so you can correct by the exact amount needed.

What does ND gel do?

Neutral density reduces the brightness of a light or window without changing its colour. LEE ND is graded by density: .3 is one stop, .6 two stops, .9 three stops and 1.2 four stops.

What is the difference between full, half and quarter gels?

They're graded strengths of the same effect. A full gel gives the maximum correction or diffusion; half, quarter and eighth give progressively less, so you can fine-tune colour temperature or softness precisely.

What is Minus Green used for?

Minus Green (a magenta gel) cancels the green spike that some fluorescent and older LED sources produce, so those lights render clean white and match your other sources on camera.

What is the LEE swatch book?

It's a booklet containing a physical sample of every LEE filter, so you can compare colours and diffusions against a light and specify the exact gel number you need.