What light does a shade give? Opal glass, clear glass, metal, rattan, linen and paper compared

A shade is not decoration around a bulb; it determines what the light does. Two pendant lights with the same shape and the same bulb give a completely different room if one is made of opal glass and the other of black metal. The first fills the whole room with soft light, the second lays a bright circle on the table and leaves the rest in semi-darkness.

So first decide what you expect from the lamp, and only then the material. If you want to fill a room, you want a shade that lets light through and spreads it. If you want to light a particular spot, you want a shade that directs the light. If you mainly want a light object, you choose a shade that shows the bulb or casts shadows, and you accept that less usable light comes out.

Why opal glass causes less glare than clear glass

Glare does not come from the amount of light, but from how bright a small surface is. Licht.de calls this luminance: how much light per square metre of a surface reaches your eye. An LED bulb in clear glass is a small, very bright point. The same bulb behind opal glass spreads the same light over the whole glass surface, so that each part is much less bright. Licht.de explicitly names opal glass and diffusers as ways to lower the visible luminance of a lamp, alongside louvres, reflectors and lenses. The French health agency ANSES also recommends warm white light for lighting in the home, and indirect lighting or lamps with a diffuser.

That explains a common mistake: a clear glass pendant light above a dining table with an ordinary clear LED bulb in it. During the day it is a beautiful object; in the evening everyone at the table looks into a bright point. If you want clear glass, choose a bulb that is made to be seen, such as a globe or a filament bulb with a low brightness, and dim it. More on that in filament bulbs: when they look good and when they do not.

Metal: light where you want it, and a dark shade

A closed metal shade lets no light through. Everything comes out through the opening, usually at the bottom, sometimes at the top as well. That gives a clear circle of light on the table or worktop and a calm, dark shade. For a dining table or an island that is exactly what you want: light on the food, not in the eyes of the person sitting opposite you.

Two details make the difference:

• The inside. A white inside reflects far more light outwards than a black one, and a gold-coloured inside makes the light warmer. How brightly a surface lights up depends directly on how much light it reflects; licht.de calculates the luminance of a matt surface with the reflectance factored in.
• How deep the bulb sits in the shade. If the bulb sits almost level with the bottom edge, everyone who is seated looks straight into the light source. A deep shade or a bulb with a shielding ring solves that. Licht.de calls this shielding the shielding angle: the larger it is, the less glare.

Ceramic and thick wood behave like metal: they are opaque, so all the light comes out through the openings.

Linen and fabric: the colour of the shade colours the light

A light fabric shade works like a soft filter. The light that passes through takes on the colour of the fabric: white linen gives neutral light, beige or natural makes it warmer, a coloured shade tints the whole circle of light. A dark fabric shade lets little through and behaves like a metal shade, with light only upwards and downwards.

Fabric and paper are close to the bulb, so keep to the maximum wattage the manufacturer states, and choose an LED bulb: it gets far less hot than an incandescent or halogen bulb. With card you often see in the product information that it has been treated with a flame retardant; that is a good sign, not a reason to fit a brighter bulb than permitted.

How large the shade of a table or floor lamp should be and at what height its bottom edge belongs is explained in table lamp and floor lamp: the right height and shade size.

Rattan, bamboo and weaves: shadows as an effect

A rattan or bamboo shade lets light through the openings between the fibres. That gives the recognisable pattern of light spots on the ceiling and walls, and that is precisely the purpose of such a lamp. The larger the openings, the sharper the pattern and the more light comes out, but also the more you see of the bulb itself.

The mistake often made here is a clear, bright bulb in an open weave. Then you see a bright little point through every gap. A frosted bulb or an opal globe bulb gives a softer pattern that still draws, but does not sting. And do not expect task lighting from a rattan pendant light: part of the light stays caught in the weave, and what comes out is divided into spots.

Smoked and amber glass: a beautiful object, less light

Tinted glass holds back part of the light. Smoked glass softens the light without colouring it much; amber glass makes it noticeably warmer and more yellow. A pendant light with amber glass can be a superb object, and in the evening it gives a glow reminiscent of candlelight. What it does not do is light a table brightly with a bulb that would be more than enough behind clear glass.

Two ways to deal with that: you deliberately choose mood lighting and provide light for reading or cooking elsewhere in the room, or you fit a stronger bulb and dim it when you want less. Do not mix too many types of tinted glass in one room: amber next to opal next to smoked reads as chance.