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Start My PlanA photometric analysis is the calculation, a photometric study is the simulation that calculation produces, and a photometric plan is the permit-ready document you submit. A "photometric report" is the outlier — it usually means one fixture's lab data (an IES / LM-79 file), not your site. So when a jurisdiction asks for a "photometric plan" or a "photometric study," it almost always wants the same thing: the scaled site drawing with a foot-candle grid.
If you are mid-project and the four words are being thrown around as if they are interchangeable, you are not imagining it — three of them nearly are, until the moment you submit for a permit. This guide draws the lines so you can hand your jurisdiction the exact document it asked for, the first time.
The four terms at a glance
Three of the four terms describe the same body of work at different stages; the fourth describes a different document entirely. The analysis runs the math, the study is the modeled result, and the plan is that result formatted for plan review. A fixture "report" sits outside the chain — it is an input, not the deliverable.
| Term | What it is | What it produces | When you need it |
|---|---|---|---|
| Photometric analysis | The illuminance calculation — fixture data run against your site geometry | Point-by-point foot-candle values | Whenever a layout has to be proven against a target |
| Photometric study | The modeled simulation built from that analysis | A readable light-level model: averages, min, max, uniformity | When you are evaluating or comparing a design |
| Photometric plan | The study formatted as a permit-ready document | A scaled site drawing + grid + fixture schedule + compliance summary | When a jurisdiction requires a lighting submittal |
| Photometric report | One luminaire's lab-measured output (IES / LM-79) | A candela distribution for a single fixture | When you are specifying or comparing fixtures, not a site |
Photometric analysis: the calculation
A photometric analysis is the calculation step. The software takes each fixture's IES file, your pole locations and mounting heights, and your site geometry, then computes the illuminance at every node on a grid. It is the engine, not the deliverable — the part that turns fixture data into foot-candle numbers.
In AGi32 or DIALux EVO, the analysis is where the point-by-point grid gets built — commonly at 10 ft spacing — and where light-loss factors are applied so the result reflects maintained foot-candles, not optimistic initial output. Skip that step and a layout can read 15–30% brighter on paper than it ever will on the ground. "Photometric calculation" is the same idea; the two terms are interchangeable in practice.
Photometric study: the simulation
A photometric study is the simulation the analysis produces — the full modeled picture of how light lands across your site, with the average, minimum, and maximum foot-candles and the uniformity ratios spelled out. If the analysis is the math, the study is the result you can read: the model that tells you whether the design works before anything is installed.
A study is where you catch the dark zone at the back of the lot, test a fixture swap, or compare two pole layouts against the same target. It is the same underlying data that becomes the plan; the difference is purpose. A study informs the design. A plan documents it for a reviewer.
Photometric plan: the permit deliverable
A photometric plan is the study turned into a document a plan reviewer can approve — a scaled site overlay with the foot-candle grid, a fixture schedule, property-line trespass values, and a compliance summary mapped to your jurisdiction's code. It is the only one of these four terms that a city actually asks you to submit.
The plan names the governing standard — usually ANSI/IES RP-8-25 plus any local thresholds — and ties every calculated value back to the modeled fixture, so the reviewer can confirm compliance without guessing. It is the deliverable our guide to photometric plans walks through layer by layer.
"Photometric report": the term that doesn't belong
"Photometric report" is the term that causes most of the confusion, because it points at two different things. Most often it means a single fixture's lab-measured data — the IES or LM-79 file that describes how that one luminaire emits light. Less often, people use it loosely for the summary pages of a study. Neither is the site document a permit needs.
That fixture data — the IES file — is an input to your analysis, not a stand-in for your plan. A manufacturer's "photometric report" for a single luminaire tells you how that product performs in a lab; it says nothing about whether your parking lot clears a 0.5 fc minimum or stays under the property-line limit. To read the deliverable itself, see how to read a photometric plan.
Why the words get used interchangeably
Here is the honest part: most of the time, the distinction does not matter. A jurisdiction that asks for a "photometric study" and one that asks for a "photometric plan" usually want the identical deliverable — the site drawing with the grid. Designers, reviewers, and manufacturers all use the terms loosely, and for everyday conversation that is fine.
The difference only becomes load-bearing at two moments. The first is when a fixture "report" gets mistaken for a site plan — it cannot pass review, because it is one luminaire's data, not a model of your site. The second is when a reviewer's written comment uses a specific word and you need your submittal to match it. When the cost of a rejection is measured in idle crew days, that precision is cheap insurance.
Which document does your jurisdiction want?
In almost every commercial permit case, the answer is the photometric plan — the site drawing, not a fixture's report. If a plan-review comment says "submit a photometric plan," "site lighting plan," "photometric study," or "lighting calculations," it is asking for the same package: the foot-candle grid, the fixture schedule, the property-line values, and the compliance summary.
If you are not sure which the reviewer means, the safe move is to provide the full permit-ready plan — it contains everything the narrower terms refer to. That is exactly what our photometric plan service produces, and the pricing page shows what a typical scope runs ($300–$2,500 for most commercial sites).
Frequently asked questions
Is a photometric study the same as a photometric plan?
In practice, almost always yes. The study is the modeled simulation of how light lands on your site; the photometric plan is that simulation formatted for permit submittal. When a jurisdiction asks for either, it generally wants the same site drawing — the foot-candle grid, fixture schedule, and compliance summary. The plan is simply the study made review-ready.
What is a photometric analysis?
A photometric analysis is the calculation that produces the numbers: the software runs each fixture's IES data against your site geometry and computes foot-candle values at every point on a grid. "Photometric calculation" means the same thing. It is the step that feeds the study, not a separate document you submit.
What does a "photometric report" mean?
Usually a single fixture's lab-measured data — an IES or LM-79 file describing how that one luminaire emits light. It is an input to your site calculation, not a substitute for it. A fixture report cannot pass plan review, because it says nothing about whether your site meets its required light levels.
Which document does my city require for a permit?
Almost always the photometric plan — the scaled site drawing with the foot-candle grid, fixture schedule, property-line values, and a compliance summary mapped to your code. If the reviewer's comment says "study," "site lighting plan," or "lighting calculations," the same permit-ready plan satisfies all of them.
Is a photometric calculation different from a photometric study?
Only in emphasis. The calculation is the math the software runs; the study is the readable result that math produces — averages, minimums, maximums, and uniformity ratios. The two terms are used interchangeably day to day. Both are stages on the way to the photometric plan you actually submit.
If a reviewer's comment has you guessing which document to submit, request a quote and we will match the deliverable to exactly what your jurisdiction asked for — turned around in 48 hours.