A lighting sample is enough when your open question is about the selected fixture itself, seen in a real setting. On its own, it cannot show coverage across a different room shape or several task zones.
If you need to know how the fixture performs in a real space, run a pilot in a zone that matches the areas you are deciding on. If you need predicted light levels across locations or across rooms that differ, a photometric layout is the better next step. Use this split as a practical planning rule, not as a guarantee of installed performance.
Choose the Next Step by the Unanswered Question
Start by naming the question you still cannot answer. Then pick the step that fits it. Each option covers a narrower or wider area, and none of them proves installed results across the whole project by itself.
| Unanswered question | Next step | What the result covers |
|---|---|---|
| How does this fixture look and work in our space? | Fixture sample | That fixture, where you placed it |
| Will it work in a real area like the ones we plan to light? | Representative pilot zone | Areas that match the pilot's geometry and tasks |
| How much light reaches locations across different rooms or task zones? | Photometric layout | Modeled coverage, based on its inputs |
Read the table from the top down. If you are judging one fixture, such as a fixture from our commercial LED lighting range or a unit from our linear high bays catalog, a sample is a sensible first step. Mount or place it where the real question lives, not on a desk in a spare office.
Move down a row when the question gets bigger than the step you are on. A sample answers questions about one fixture in one place. A pilot answers a real-setting question for areas like the one you tested. Once the decision involves spaces with different ceiling heights, room shapes, or tasks, the question is about coverage. A local test cannot settle that.
The sample and pilot rows are rules of thumb for project planning, not lab-validated findings. Their value comes from keeping each conclusion tied to the space that produced it.
Use a Pilot Zone Only for Conditions It Represents
A pilot zone can inform the wider decision only as far as its conditions match the areas you plan to light. Having tested one area is not the same as having tested the project. Before you apply a pilot result anywhere else, compare that area's geometry and tasks with the zone you piloted.
Here is an illustrative case. A facility manager pilots new fixtures over one bay of storage racks in a warehouse. The plan is to relight the whole building, which also has a quality-inspection bench and a lower-ceiling packing area. The pilot bay has the same ceiling height, rack spacing, and picking task as the other storage bays. So the result is useful for those bays.
The pilot says nothing reliable about the inspection bench or the packing area. Those spaces differ in geometry, in the task being done, or in both. Treat them as untested, even if the pilot bay looked great. Our guide to planning storage and inspection zones goes into when one layout can serve both and when the tasks need separate treatment.
To turn this into a decision, write two short lists after the pilot:
- Represented: the areas that share the pilot's room geometry and task conditions. The pilot result can guide choices here.
- Unlike or untested: every area with a different ceiling height, room shape, layout, or task. Do not carry the pilot result into these areas.
If the second list is empty, the pilot may answer your question. If it includes areas with different geometry or task zones, take those areas to the photometric layout path below.
Choose a Photometric Layout for a Coverage Question
Choose a photometric layout when the open question is predicted light levels across locations, rooms, or task zones rather than a single space you can walk into. A layout models coverage before installation without proving a sample or pilot was wrong.
What the Modeled Methods Address
Two calculation methods show what a layout is built to answer. The VA Lighting Design Manual, written for VA facility lighting design, defines the point method as predicting illuminance at various points and locations from luminaire photometric data. In plain terms, it estimates how much light lands on a specific spot, such as one end of an aisle or a workbench.
The same manual describes the lumen method. It relates the number and types of luminaires and the room characteristics to the average illuminance on the work plane. That answers a different question: about how many fixtures of a given type it takes to light a room's working surface on average.
Both methods produce calculated estimates. A result depends on the data and assumptions put into it. It is not a guarantee of installed light levels, product fit, or code compliance.
Inputs and Assumptions to Assemble
A layout can only be as accurate as its inputs, so gather these before the modeling discussion:
- Luminaire photometric data for each fixture you are considering. This is the manufacturer's file that describes how the fixture distributes light.
- Room characteristics for each distinct space, such as dimensions, mounting conditions, and surface reflectance. Teams working on a retrofit can record existing site conditions with photos and measurements before ordering.
- Calculation targets: the specific locations or work-plane areas the model must cover. Flag every place where geometry or tasks change. For multi-area or phased projects, it helps to organize zones and inputs in one project brief.
- Existing-condition inventory, if you are relighting an existing building. The USGBC existing-building lighting inventory steps cover luminaire characteristics, light-distribution sources, reflectances, and illuminance ratios. It was written for LEED existing-building work, so use it as an organizing checklist, not as a required input list.
Once these inputs are ready, a modeled answer is within reach. We offer a free layout service for lighting simulations and project quotes, and you can share the inputs above through our online lighting layout tool.
FAQs
Can a photometric layout replace a physical sample completely?
Not always. A layout calculates coverage from photometric data and room inputs, but it does not let your team see the fixture in your own space. If the open question is how a fixture looks and works in person, a sample can still be worth having alongside the model.
Does a modeled layout confirm that a project meets code?
No. A layout gives calculated estimates, and lighting requirements vary by jurisdiction across the US. A qualified lighting designer, an engineer, or the local authority having jurisdiction makes the compliance call for your specific project.
Can a pilot and a layout run on the same project?
Yes, because they answer different questions. One workable order is to model coverage across all zones first. Then pilot the chosen fixture in one representative zone to check the real-setting question there before committing to that zone type.
What if the existing fixtures are discontinued and have no photometric data?
Record what you can about those fixtures and mark the missing data as an open input. The USGBC existing-building guidance notes that discontinued luminaires may need measurements. Tell whoever runs the layout which values were measured and which were estimated.
