Lighting a painting looks like a matter of spotlights, but it is decided earlier: where the track runs, how bright the room is, what visitors should see first. The spotlight comes last. With the right geometry a few watts are enough; with the wrong one, no spotlight can save it.
This page gives the figures, with a calculator for distance from the wall, beam and candelas on your wall. They apply to a museum, a gallery, a studio or a living room. Conservation (annual dose, damage per lumen, UV) is covered in the museum lighting guide.
1. Ambient light and accent light: two different jobs
- ambient light lets people move, find their way and read the space;
- accent light makes the work visible and tells people where to look.
The most common mistake is too much ambient light. The eye adapts to the average brightness of the room: in a bright room even 150 lux on a painting look dim. What matters is the ratio between work and wall, not the absolute value.
| Work / wall ratio | Effect | Where |
|---|---|---|
| 1:1 | Flat, no hierarchy | Offices, corridors |
| 3:1 | The work stands out naturally | Full walls, homes |
| 5:1 | The work is clearly the focal point | Museums, galleries |
| 10:1 | Dramatic, the work "floats" in the dark | Single works, sculptures |
With sensitive works (paper, textiles) the ratio is obtained by lowering the ambient light, not by raising the light on the work.
2. The angle: 30 degrees, and why
Aim at the centre of the painting at about 30 degrees from the vertical. Varnish and glass act as a mirror: at 30 degrees the reflection falls on the floor in front of the viewer; at smaller angles it rises to eye level. Work between 28 and 35 degrees; above 40 the frame shades the top.
3. Distance from the wall and beam
| Spotlight height | Distance from wall | Throw | Beam, painting 1.2 m wide | Beam, painting 0.6 m wide |
|---|---|---|---|---|
| 2.70 m | 0.64 m | 1.27 m | 51° | 27° |
| 3.00 m | 0.81 m | 1.62 m | 41° | 21° |
| 3.30 m | 0.98 m | 1.96 m | 34° | 17° |
| 3.60 m | 1.15 m | 2.31 m | 29° | 15° |
| 4.00 m | 1.39 m | 2.77 m | 24° | 12° |
| 4.50 m | 1.67 m | 3.35 m | 20° | 10° |
| 5.00 m | 1.96 m | 3.93 m | 17° | 9° |
That is why the track must be installed at the right distance before knowing which paintings will arrive. Above 4.5 m a suspended track is better.
Calculator: the right spotlight for your painting
4. How many lux, and how many candelas
| Category | Materials | Illuminance |
|---|---|---|
| Highly sensitive | Watercolours, drawings, prints, textiles, photographs | 50 lux |
| Sensitive | Oil and tempera paintings, panels, wood, ivory, lacquer | 150 lux |
| Low sensitivity | Stone, metal, ceramics, glass, mosaic | 300 lux + |
At 30° aiming the light reaches the wall at 60° from the perpendicular, so:
With a 3 m mounting height (throw 1.62 m) an oil painting at 150 lux needs about 780 cd; at 4 m (throw 2.77 m) about 2,300 cd. A painting needs control, not power. Every ACSE product page has a simulator giving lux and spot diameter at your distance.
5. Uniformity: where to aim the beam centre
The bottom of the painting is farther away and receives more oblique light: with a full beam, on a 1 m tall painting lit from 3 m, the bottom edge gets about five times less light than the top. Aim the beam centre slightly below the centre of the painting, use an oval optic for rectangular works, two spotlights for works wider than 2 m, a snoot or framing projector when the light must stop at the frame.
6. Reflections: geometry, not power
Dimming does not remove a reflection. Imagine the glass as a mirror and ask where the image of the spotlight ends up. Remedies: raise the angle towards 35°, use well shielded sources (snoot, honeycomb), tilt the painting forward a few degrees, anti-reflective glass where allowed.
7. Sculptures and three-dimensional objects
A volume is read through shadows. Use a key light from above and to one side (30-45°), a fill light from the opposite side at one third to one half, and optionally a back light to separate the outline. Avoid a single light from straight above and light from below. For showcases see the museum guide and the showcase calculator.
8. Full walls: spotlights or wall washers
One spotlight per painting when works are spaced out; wall washers when the wall is full and needs even light from top to bottom. A wall washer on a single painting lights more wall than work.
9. Colour of light and rendering
3000 K is the usual choice for old masters and gilding; 3500-4000 K for contemporary art and photography. All spotlights in a room need the same white, within 3 MacAdam steps. Colour rendering matters more: CRI at least 90 with a declared R9 (saturated red), see CRI 90 and R9.
10. Frequent questions
About 30 degrees from the vertical, measured at the centre of the painting. This angle sends the reflection of the spotlight towards the floor, away from the viewer's eyes, without being so grazing that the frame casts a shadow. The working range is 28 to 35 degrees: below 25 the source is reflected in the glass or varnish, above 40 the frame starts to shade the picture.
The height of the spotlight above the centre of the painting multiplied by 0.58 (tangent of 30 degrees). With a 3 m ceiling and the painting centre at 1.60 m the spotlight goes 81 cm from the wall; with a 4 m ceiling, 1.39 m. The calculator on this page does it for any height.
The materials decide: 50 lux for paper, watercolours, drawings, textiles and photographs; 150 lux for oil and tempera; 300 lux or more for stone, metal, ceramics and glass (CIE 157). At home or in a private gallery you can go higher, but the same principle applies: the ratio between painting and wall matters more than the absolute value.
Ambient light lets people move and read the space; accent light makes the work visible. If the room is already bright, the work no longer stands out even with many lux. As a rule the work is kept 3 to 5 times brighter than the surrounding wall, up to 10 times for a dramatic effect.
Because the viewer's eye lies on the direction in which the glass or varnish returns the image of the source: angle of reflection equals angle of incidence. A spotlight too low or too close to the wall means a reflection at eye level. It is solved by moving the spotlight, not by dimming it.
With at least two lights: a key light from above and to one side at about 30-45 degrees, which draws the forms with shadows, and a weaker fill light from the opposite side (one third to one half) that opens the shadows without erasing them. A single light straight from above flattens volumes and darkens faces.