Every rig brief eventually becomes the same question: how many fixtures do I need, and how much light is enough? The usual answer — “about eight” or “one per metre” — comes from habit, not arithmetic. This guide replaces it with a method you can run in five minutes on a napkin, using the two numbers that actually decide coverage: the illuminance you need where the audience is looking, and the beam spread of the fixture you already own.
In this guide
Rig sizing has exactly two inputs. First, how much light the subject needs, expressed as illuminance in lux. Second, how wide the fixture throws it, expressed as a beam angle in degrees. Everything else — wattage, LED count, price, weight — influences those two numbers but does not replace them.
This is why two fixtures with identical 19 × 15W engines can need completely different quantities. At a 10° beam the same engine concentrates everything into a small pool and is extremely bright in that pool. At 60° it spreads the same output over a much larger area and is dimmer everywhere. Same wattage. Same LED count. Different job.
Before counting fixtures, decide the beam angle each position needs. A rig designed by beam angle almost always comes out smaller and cheaper than one designed by “one light per area”.
The three units are routinely mixed up, and the confusion is what makes rig sizing feel like guesswork. They measure different things at different points in the light path.
| Term | What it measures | Where it is measured | Use it for |
|---|---|---|---|
| Lumen (lm) | Total light output of a source in all directions | At the source | Comparing the efficiency of two fixtures with the same beam angle |
| Lux (lx) | Illuminance — light landing on a surface | At the subject or the floor | Deciding whether the stage is bright enough |
| Watt (W) | Electrical power drawn from the wall | At the plug | Circuit and distro planning only |
| Candela (cd) | Luminous intensity in one direction | At the fixture face | Beam-angle maths and throw-distance falloff |
Wattage appears in marketing as a proxy for brightness because it was once a reasonable proxy for incandescent sources. That link broke when LED efficiency diverged. A 200W LED wash and a 200W halogen par draw the same power and produce wildly different illuminance. Wattage tells you what the generator and the breaker need to know. It tells you nothing about whether the audience can see the performer.
Double the throw distance and you get a quarter of the illuminance on the subject — before accounting for the beam widening. This is why the same fixture that lights a small stage comfortably will look weak from a high front-of-house position, and why height matters as much as horizontal distance.
These are practical working ranges for live performance and events, drawn from common stage-lighting practice. They describe the light reaching the performer or the focal area, not the fixture output, and they assume a normal amount of contrast in the design — a high-contrast look deliberately runs the key light at the top of the range.
| Venue or use | Typical target | Notes |
|---|---|---|
| Small club / bar stage | 300 – 800 lx | Tighter rooms, shorter throws, lower ceilings. Easier than it sounds. |
| Mid-size theatre or live venue | 500 – 1,200 lx | The range most touring wash rigs are designed around |
| Large theatre / arena | 1,000 – 2,000 lx | Long throws force narrow beams or higher-output fixtures |
| Corporate / conference stage | 500 – 1,000 lx | Even, low-contrast coverage matters more than punch |
| Camera or broadcast | 1,000 – 2,000 lx | Subject illuminance should sit well above ambient for correct exposure |
| Ambient / background wash | 100 – 300 lx | Decorative colour on walls, not task lighting |
Illuminance targets vary by production, camera package and artistic intent. Use them as a sanity check on a design, never as a substitute for looking at the stage during a focus session.
To convert a target illuminance into a fixture count, you need the total luminous flux the design has to deliver and the throw distance to each position. The working form is:
Lumens required = lux target × area to be lit ÷ utilisation factor
Then: fixtures required = lumens required ÷ usable lumens per fixture
The utilisation factor (often 0.3 – 0.5 for stage wash) accounts for the light that spills outside the target area, is absorbed by scenery, or simply misses because beams are round and stages are rectangular. Skipping it is the most common cause of under-specifying.
The instructive part is step four. The flux calculation said two fixtures. Practical stage geometry says six. Both are correct answers to different questions, and a rig sized only on flux will have two blazing hotspots and dark corners.
Because illuminance falls off with distance and spreads with angle, the beam angle you choose per position changes the required fixture count more than any other decision. Motorized zoom exists precisely so that one fixture can cover positions of different throw distances without a second purchase.
| Beam angle | Rough pool at 5 m | Best at | Typical use |
|---|---|---|---|
| 10° – 15° | 0.9 – 1.3 m | Long throw | Feature positions, aerial beams, tight pools on a performer |
| 25° | ≈ 2.2 m | Medium throw | The general-purpose workhorse angle for stage sections |
| 40° – 45° | 3.6 – 4.1 m | Short throw | Front wash, small stages, low ceilings |
| 60° – 67° | 5.8 – 6.6 m | Very short throw | Wall and cyclorama wash, room coverage from low trim heights |
Read the top row against the bottom row: the same fixture at 10° and at 67° covers a pool roughly seven times wider in each direction — nearly fifty times the area. Nothing else in rig design changes the lighting outcome by a factor that large.
A fixed 25° fixture costs less than a zoom. If the venue has one trim height and one stage depth, that is a real saving. If your schedule covers rooms of different sizes, you will buy the second set of fixed fixtures within a year — which is what the zoom would have replaced.
The purpose of a multi-fixture wash is not to add brightness. It is to remove the shadows and gaps that a single source produces, and to make colour mixing smooth. Both of those are achieved by overlap, not by quantity.
A conventional three-point approach for a stage section sits a key light off-axis, a fill on the opposite side at lower intensity, and a back light behind the performer to separate them from the backdrop. That is three fixtures doing three different jobs. Scale the approach along the stage width and you get overlapping pools from a handful of positions, each covering a neighbour’s gap.
Eight fixtures spread evenly and aimed vaguely produce the same average illuminance as four fixtures aimed deliberately — with worse colour mixing, more visible gaps and twice the cabling. Aim beats quantity.
Putting the method together for the most common brief: a 24 m² stage, front truss at 4 m, a 600 lx target across the acting area, and a coloured backdrop wash behind.
Front wash — 4 positions
Moving feature — 2 positions
Backdrop wash — 2 positions
Key light, camera-friendly
Illustrative list at current published prices. Beam angle, trim height and throw distance should be confirmed against the actual venue before ordering.
Notice that no count in this plan came from dividing lumens. Each position exists because of a job: front coverage, reach, backdrop colour, or camera accuracy. The flux calculation confirmed the light was sufficient. It did not choose the rig.
For a 24 m² stage at a 600 lx working target with a realistic utilisation factor of 0.4, the design needs roughly 36,000 lumens leaving the fixtures. That is a flux figure, not a fixture count — the number of fixtures is then set by beam angle and how many positions are needed to cover the area without gaps.
For a small club or bar stage, 1,000 lx is generous — typical targets there sit between 300 and 800 lx. For a mid-size venue it is at the upper end of the normal 500–1,200 lx range. For a large theatre or an arena with long throws, 1,000 lx is on the low side and usually means narrow beams or higher-output fixtures rather than more fixtures.
Wattage measures electrical power drawn from the wall. Brightness at the subject depends on optical efficiency, beam angle and throw distance. LED efficiency varies enough between engines that two fixtures with identical wattage can differ substantially in illuminance. Wattage remains the right number for sizing circuits and distro.
Narrow the beam first, if the position allows. Reducing beam angle concentrates the light you already own onto the area that needs it, at no extra cost, weight or cable. Add fixtures when the problem is coverage or overlap rather than intensity.
For a typical 6 m stage with the truss at 3–4 m, 25° to 45° is the practical working range. Lower trim heights favour wider angles because the throw is shorter; higher front-of-house positions need narrower beams to keep illuminance up. Motorized zoom lets one fixture cover both without a second purchase.
Any reasonable meter is more useful than no meter. The targets themselves are ranges with hundreds of lux of latitude, so a meter that is within a few percent is entirely adequate for checking a design. What matters is measuring at the same points each time so the numbers are comparable between venues.
Illuminance targets in this article are general working ranges drawn from common stage-lighting practice, not standards, and are provided for planning purposes. Actual requirements vary with production design, camera package, venue dimensions and local regulation. Product specifications and prices are those published on sanyilights.us at the time of writing and are subject to change. Verify all electrical and rigging work against local codes and the fixture datasheets before installation.
