Learning Lighting

See how a car wash photometric plan verifies foot-candle levels, uniformity, fixture placement and spill light using real IES-based calculations.

A car dealership photometric plan shows how light will perform across vehicle display rows, customer parking, drive aisles, frontage areas and perimeter zones before the fixtures are installed. The plan uses the actual IES photometric data for the selected luminaires to calculate point-by-point light levels across the site. Dealership lighting is different from a normal parking lot. The vehicles themselves are part of the merchandise, so the display lot often requires higher illumination than customer parking or perimeter areas. At the same time, the design still needs to control glare, spill light and abrupt changes in brightness. This guide explains how dealership lot lighting is calculated, what foot-candle and uniformity metrics matter, how pole height affects the layout, and how a real Stetra Lighting dealership project was designed and verified. What Is a Car Dealership Photometric Plan? A car dealership photometric plan is a computer-calculated lighting study of the exterior vehicle display lot and surrounding site. The designer models the property, buildings, parking rows, drive aisles and fixture locations, then calculates illuminance using the proposed luminaires’ IES files. pole and fixture locations mounting heights point-by-point foot-candle values average, minimum and maximum illuminance uniformity ratios display-lot and customer-parking zones false-color or iso-foot-candle distribution property-line light spill where required fixture wattage, lumens, CCT and light-loss factor fixture totals and connected load For the broader process, see our complete guide to photometric plans. Why Car Dealership Lighting Is Different From Standard Parking-Lot Lighting A dealership parking lot has two jobs: it must provide safe circulation, and it must present the vehicle inventory clearly after dark. That often means different calculation zones with different lighting priorities. Vehicle display areas usually need stronger, more uniform illumination than ordinary customer parking. Drive aisles and perimeter areas can be lower, while frontage areas may need careful glare and spill-light control. Current industry guidance also emphasizes treating display lots, customer parking and frontage as separate zones rather than relying on one overall site average. That is especially important on large dealership campuses. Car Dealership Foot-Candles: What Level Is Typical? Dealership Area Common Planning Range Design Note Exterior vehicle display lot 20-50 fc Higher illumination supports vehicle presentation after dark. Customer parking / drive aisles Lower than primary display areas Should be coordinated with site circulation and local criteria. Building entrances / facade zones Project-specific Often coordinated with brand visibility and pedestrian use. Perimeter / property line Jurisdiction-specific Light trespass limits can be much lower than display-lot levels. The values above are general planning guidance, not universal code requirements. Final criteria should be confirmed for the actual project, owner standards and local jurisdiction. Real Car Dealership Photometric Plan Example The project below is a real Stetra Lighting dealership study for a large multi-building automotive campus. The site contains extensive vehicle inventory, multiple dealership buildings, circulation drives and perimeter roads, making it a strong example of why dealership lighting should be treated as a multi-zone photometric problem. 3D overview of the dealership site showing the large exterior display areas and how the lighting is distributed around multiple buildings. Point-by-Point Foot-Candle Grid Full-site point-by-point calculation showing the dealership buildings, vehicle display areas, poles and calculated foot-candle values. The point-by-point grid is the core technical output of the photometric plan. Each number represents calculated illuminance at that location. The grid makes it possible to see where the design is strong, where values drop between poles, and whether the transitions between display areas and perimeter zones are controlled. Closer Look at the Vehicle Display Areas Detailed point-by-point view showing how the fixture grid overlaps across dense vehicle display rows. Closer calculation view around one of the dealership buildings showing the relationship between pole positions and vehicle-row illumination. Calculated Site Result The overall site average for this Stetra project was 12.7 foot-candles. That number should not be interpreted as the target for every dealership or every display zone. It is the average across this specific project’s overall site calculation surface. Individual display rows contain much higher values, while perimeter and transition areas are lower. Why Uniformity Matters at a Dealership Uniformity affects both visibility and presentation. A dealership with bright hot spots directly under poles and dark gaps between them can still produce an acceptable average, but the site will not look evenly illuminated. For a deeper explanation, see our guide to lighting uniformity ratios. False-Color Analysis of the Dealership Lot False-color view of the dealership site showing the strongest display areas in orange and red and the gradual falloff toward the perimeter. Fixture Schedule From the Real Project Quantity: 243 fixtures Input power: 298.3 W per fixture Lumen output: 40,609 lm per fixture Mounting height: 35 ft Color temperature: 5000 K Light-loss factor: 0.80 Total connected load: 72,487 W Total lumens: 9,867,987 lm Average efficacy: 136.1 lm/W Fixture schedule from the real dealership study showing the area-light specification and total project quantities. Why 35-Foot Pole Height Matters In this example, the main luminaires are mounted at 35 ft. A higher mounting height allows each fixture to cover a wider portion of the display lot, which can help reduce the number of poles and improve overlap between adjacent distributions. Display-Lot Optics and Pole Spacing Large dealership sites often use wide-area optics to cover multiple vehicle rows from tall poles. Type III, Type IV or Type V distributions may be appropriate depending on pole position, perimeter conditions and the direction in which the light needs to travel. Light Trespass and Roadway Frontage Dealership display lots are often intentionally bright, but the property line may be close to public roadways, neighboring commercial properties or residential areas. That makes perimeter control an important part of the photometric plan. There is no single U.S. property-line limit that applies to every dealership. The correct limit must be confirmed from the local ordinance or project criteria. Real Installed Result Real after-installation aerial image of the dealership site. The installed result provides a useful comparison with the calculated photometric model. This completed-project image is especially useful because it shows the

A gas station photometric plan shows how light will perform across the fuel canopy, pump islands, drive aisles and surrounding site before the fixtures are installed. It uses the actual IES photometric data for the selected luminaires to calculate point-by-point foot-candle or lux values. Gas stations are different from ordinary parking lots because one project can combine a very bright canopy area with much lower light levels at the edge of the site. A good lighting plan has to provide clear visibility around the dispensers while also controlling glare, spill light and abrupt transitions into adjacent properties or roadways. This guide explains how gas station canopy lighting is calculated, what results should be reviewed, and how a real Stetra Lighting project was analyzed. What Is a Gas Station Photometric Plan? A gas station photometric plan is a computer-calculated lighting study for the fueling canopy and the surrounding exterior site. The designer models the canopy geometry, dispenser locations, building and paved areas, then places the proposed luminaires at their actual mounting conditions. canopy fixture locations and quantities point-by-point foot-candle values average, minimum and maximum illuminance uniformity ratios drive-aisle and parking light levels property-line or perimeter spill light where required fixture mounting conditions and IES files false-color or iso-foot-candle visualization fixture schedule and design assumptions For the broader process, see our complete guide to photometric plans. Why Gas Station Canopy Lighting Needs Its Own Calculation The fuel canopy is a concentrated task area. Customers need to see dispensers, card readers, hoses, vehicles and walking surfaces clearly, but the canopy can sit close to public streets, parking areas or neighboring properties. That creates two design problems at the same time: provide enough useful light under the canopy, and control how quickly that light falls off outside the fueling zone. Current exterior-lighting guidance often treats canopy areas as separate calculation grids, and some jurisdictions explicitly require separate canopy summary values. Gas Station Canopy Foot-Candles: What Level Is Typical? There is no single foot-candle requirement that applies to every gas station. The correct target depends on the jurisdiction, owner standards, fixture mounting height, canopy geometry, visual tasks and measurement plane. Area Common Planning Range Design Note Fuel pump / canopy area 20-50 fc General planning range; confirm project requirements. Drive aisles / circulation Lower than canopy zone Coordinate with site-lighting and local exterior criteria. Parking / convenience-store site Project-specific Depends on use, zoning and surrounding conditions. Property line Jurisdiction-specific Light-trespass criteria can be much lower than fueling-area levels. The 20-50 fc value is a general planning range, not a universal code requirement. Some jurisdictions establish substantially different minimums, maximums or uniformity criteria for service stations. Real Gas Station Photometric Plan Example The project below is a real Stetra Lighting gas station study. The model includes the fuel canopy, pump islands and surrounding site so that canopy performance can be reviewed together with the light falling outside the immediate fueling area. 3D overview of the gas station lighting model showing the canopy lighting and how it transitions into the surrounding site. Point-by-Point Foot-Candle Calculation Point-by-point gas station calculation showing high illumination under the canopies and the gradual falloff into the surrounding site. The point-by-point grid is the core of the photometric plan. Each value represents calculated illuminance at that location. Under the canopy, values are much higher because fixtures are mounted directly above the fueling area. Moving away from the canopy, the numbers fall progressively into the surrounding site. Photometric Results From the Example For this Stetra project, the calculated results were: Calculation Area Average Maximum Minimum Avg/Min Max/Min Gas station canopy area 70.6 fc 111 fc 25.4 fc 2.78:1 4.37:1 Overall site 19.5 fc 113 fc 0.043 fc — — These values belong to this specific project. They are not presented as recommended targets for every gas station. Why Average Foot-Candles Are Not Enough An average value can hide both dark areas and hot spots. For gas stations, also review minimum illuminance, maximum illuminance, average-to-minimum ratio, maximum-to-minimum ratio and perimeter values. See our guide to lighting uniformity ratios. False-Color Analysis: Seeing the Light Distribution False-color analysis makes the concentration of light beneath the fuel canopies and the transition into the surrounding site easy to see. The false-color view turns the numerical calculation into a visual map. In this example, the red and orange zones show the highest illumination under and around the canopies. The colors transition through yellow, green and blue as the calculated light level decreases farther from the fueling area. 3D View From the Fueling Area Ground-level 3D render showing the canopy lighting from the customer’s point of view around the fuel dispensers. A ground-level 3D view helps the owner and project team understand the lighting from the user’s perspective. It shows how the canopy fixtures relate to the pump islands, columns and paved area in a way that a plan view cannot. Canopy Lighting vs. Site Lighting The canopy and the rest of the site should not automatically be treated as one calculation area. Their purposes are different. The canopy is a high-activity task zone; surrounding parking, circulation and property-line areas normally require lower levels. Separate surfaces make it possible to evaluate each area against the correct criteria. Light Trespass and Property-Line Calculations Gas stations can be challenging near residential properties, public roads or other commercial parcels because the canopy is bright and often close to the site edge. Depending on the jurisdiction, the photometric plan may need horizontal or vertical foot-candle readings at the property line, a separate light-trespass plan, fixture shielding information or cutoff/BUG documentation. The correct approach is to check the actual local ordinance rather than assume one national property-line limit applies everywhere. Fixture Placement Under the Canopy Canopy fixtures are typically arranged to provide overlapping distributions across the fueling area. Spacing is affected by canopy height, fixture photometric distribution, lumen output, recessed or surface mounting, pump-island geometry, column locations, required light levels, glare and perimeter-control goals. Why the IES File Matters The IES file describes how a

A warehouse photometric plan shows how much light will reach the floor, aisles, storage areas and work zones before the lighting is installed. Instead of choosing high-bay fixtures by wattage or lumen output alone, the plan uses the actual IES photometric data for each luminaire to calculate point-by-point light levels across the space. For warehouses, that matters because ceiling height, fixture optics, rack layout and the type of work being performed can change the lighting result dramatically. A layout that produces enough average light can still have dark areas, poor uniformity or excessive light directly below fixtures. This guide explains what a warehouse photometric plan includes, typical planning light levels, how high-bay fixtures are spaced, and what the calculation results actually mean. It also includes a real Stetra Lighting warehouse example. What Is a Warehouse Photometric Plan? A warehouse photometric plan is a computer-calculated lighting study of an industrial or storage space. The warehouse geometry is modeled, the selected luminaires are placed at their intended mounting heights, and the lighting software calculates illuminance across defined calculation surfaces. fixture locations and quantities high-bay mounting heights point-by-point foot-candle or lux values average, minimum and maximum illuminance uniformity ratios false-color lighting distribution fixture model, wattage, lumen output and CCT lighting power density where needed calculation assumptions such as light-loss factor If you are new to photometric calculations, start with our complete guide to photometric plans. Why Warehouses Need Photometric Calculations Warehouse lighting is highly dependent on geometry. Two fixtures with similar wattage and lumen output can create very different results if their optics, mounting heights or spacing are different. A photometric calculation helps answer practical questions before installation: Are the aisles bright enough? Is the floor uniformly illuminated? Are there dark areas between fixture rows? Is the layout over-lighted? Could fewer fixtures meet the same target? Will a different distribution work better at the proposed ceiling height? This makes the photometric plan useful for new construction, LED retrofits, fixture substitutions, design coordination and projects where the owner, engineer or reviewing authority wants documented lighting performance. Warehouse Lighting Levels: How Many Foot-Candles Are Needed? There is no single correct foot-candle level for every warehouse. The appropriate target depends on the visual task, occupancy, storage method, equipment, traffic and project requirements. Warehouse Area Common Planning Range Design Consideration Inactive / low-activity storage 5-10 fc Basic visibility with limited activity General storage / active warehouse 10-30 fc Typical storage, circulation and material handling Picking / packing areas 30-50 fc Reading labels, sorting and repeated visual tasks Detailed inspection / fine work 50 fc and higher Higher visual demand; task-specific criteria should be confirmed These are practical planning ranges, not universal code requirements. Final light levels should be selected for the actual task and verified against the project specifications, applicable standards and local requirements. The important point is that a warehouse should not automatically be designed to one light level everywhere. A bulk-storage area may have a different target than a packing station, loading area or inspection zone. Real Warehouse Photometric Plan Example The following example is from a real Stetra Lighting warehouse calculation. The modeled floor area is approximately 381 ft by 195 ft. The design uses a regular high-bay grid to provide consistent coverage throughout the open warehouse. Point-by-point warehouse photometric plan showing the high-bay fixture grid and calculated foot-candle values. The point-by-point values make it possible to evaluate more than the average. They show where illumination rises or falls throughout the floor and whether the fixture spacing creates consistent coverage. Warehouse Photometric Results: Average, Minimum and Uniformity For this example, the calculated warehouse results are: Metric Calculated Result Average illuminance 32.7 fc Maximum illuminance 36.7 fc Minimum illuminance 15.1 fc Average : minimum 2.17 : 1 Maximum : minimum 2.43 : 1 Warehouse calculation sheet showing the fixture layout together with average, minimum, maximum and uniformity results. Average illuminance alone does not tell the full story. A warehouse could have a strong average while still containing dark areas. That is why minimum values and uniformity ratios are checked together with the point-by-point grid. For more on this metric, see our guide to lighting uniformity ratio. High-Bay Fixture Selection in the Example Quantity: 97 fixtures Input power: 149.7 W per fixture Lumen output: 27,000 lm per fixture Mounting height: 36 ft Color temperature: 5000 K Light-loss factor: 0.90 Total connected load: 14,521 W Total lumens: 2,619,000 lm Calculated lighting power density: 0.20 W/ft² Fixture schedule from the warehouse study showing the high-bay specification, quantity, mounting height and calculated totals. The important design input is not simply “150-watt high bay.” The photometric calculation uses the fixture’s actual light distribution. Two nominally similar high bays can require different spacing because their optics and candela distribution are different. Why Mounting Height Changes the Warehouse Layout Mounting height directly affects the size and intensity of the light pattern on the working plane. A higher luminaire can spread light over a larger area, but the illuminance at the floor changes as the distance increases. A lower mounting height may produce stronger light directly below the fixture while requiring tighter spacing for uniform coverage. That is why fixture quantity should not be determined from lumens per square foot alone. The IES file, optic, mounting height and room geometry need to be calculated together. How High-Bay Fixtures Are Spaced High-bay spacing is usually developed as a grid and then tested photometrically. The designer evaluates the spacing relative to mounting height, fixture distribution and target light level, then adjusts the rows until the required coverage and uniformity are achieved. In an open warehouse like this example, a regular grid can work very well because there are few obstructions. A racked warehouse is different: fixture rows often need to coordinate with the rack aisles so that light reaches the floor and vertical storage faces rather than landing primarily on top of the racks. False-Color Analysis: Seeing the Distribution False-color warehouse analysis. The color scale makes changes in illuminance across the floor easy to

A photometric plan lets project teams verify light levels, uniformity, glare and spill light before fixtures are installed. Learn which projects benefit most, what reviewers may request and what to send for an accurate calculation.

Daylight can make an interior feel open, comfortable and connected to the outdoors. It can also create screen reflections, harsh contrast, overheated zones and direct sun in places where it interferes with work or rest. A daylight calculation predicts how natural light will enter and move through a building before construction or renovation decisions become expensive to change. It helps architects, interior designers, contractors and property owners evaluate windows, skylights, roof lights, room layouts and shading strategies using a model of the actual project. Short answer: A daylight calculation is useful when windows, skylights or roof lights could affect comfort, screen visibility, work areas, interior finishes or the electric-lighting design. The study turns changing sun and sky conditions into visual and measurable information the project team can act on. What does a daylight calculation show? A professional daylight study can answer several different questions. The correct calculation scope depends on the decisions the project team needs to make. The study may evaluate: Where direct sunlight reaches floors, walls, desks, screens or seating How daylight changes by hour, date and season Whether a TV wall or monitor is exposed to distracting brightness How evenly daylight reaches deep parts of a room How windows, roof lights and skylights interact Whether a proposed shade or curtain reduces direct sun effectively How interior reflectance and glazing transmission affect brightness When electric lighting may still be needed The result is not simply a rendering. It is a decision tool. The model should be connected to a specific question, such as whether to move a desk, resize a skylight, add external shading or coordinate daylight-responsive electric-light controls. When should you request daylight analysis? Consider a daylight study before finalizing glazing, skylights, shading or sensitive room layouts. It is especially valuable when: A room has large areas of glass A TV, display or monitor faces a window Desks sit close to windows or beneath roof openings Direct sun could affect artwork, products or finishes A skylight may create excessive brightness or glare The team is comparing shade, curtain or blind options Daylight needs to be coordinated with the electric-lighting layout A project has explicit daylight-performance or sustainability goals Early analysis leaves more practical options available. A window can be resized, a screen relocated or a shading strategy integrated into the architecture. After construction, the same problem may require a compromise that blocks useful daylight along with the glare. Daylight review for TV walls and display areas Screens are sensitive not only to direct sun but also to high background brightness and reflections. A room may appear attractive while the display remains difficult to view during particular hours. For a TV wall or display, the model can place a calculation surface directly where visibility matters. The team can then compare time-based conditions and test whether curtains, roller shades, room-darkening blinds, external shading or a revised layout provide an appropriate response. 15:00 — daylight distribution before the strongest late-afternoon condition. 16:00 — changing sun position begins to alter brightness near the viewing area. 18:00 — false-color analysis identifies the brightest areas on and around the TV wall. 19:00 — a controlled condition demonstrates how shading changes the visual environment. The most useful comparison uses the same camera position, model assumptions and evaluation surface for each option. That allows the project team to see the effect of the design change rather than a change in presentation. Daylight calculations for desks and home offices Natural light can support an enjoyable workplace, but direct sun and strong contrast may interfere with reading, writing and screen-based tasks. A desk next to a window can receive useful diffuse daylight in the morning and uncomfortable sun later in the day. For work areas, daylight analysis may consider: Illuminance on the working plane Direct sun on the desk surface Reflections on monitors Brightness differences between windows and the surrounding room Desk orientation relative to glazing The effect of roof openings and vertical windows together Shading options for critical hours 16:00 — useful natural light reaches the desk and surrounding work area. 17:00 — the study tracks the changing balance between window light and the room interior. 18:00 — false color helps identify high-brightness zones that may affect the task area. 19:00 — lower daylight indicates when electric task lighting becomes more important. The goal is not always to maximize daylight. A successful work environment balances useful natural light with screen visibility, manageable contrast and reliable electric lighting when daylight falls below the project target. Why skylights and roof lights need special attention Roof openings can bring daylight deeper into a space than vertical windows. Because they receive light from the sky and, at certain times, direct sun from above, they may also create concentrated brightness on floors, furniture and work surfaces. A skylight daylight calculation can test: Opening size and position Shaft geometry and interior finish Glazing transmission Direct-sun paths at critical dates and hours The effect of diffusing material Internal or external shade options Interaction with vertical windows The objective is not automatically to cover the skylight. Analysis helps determine whether the opening works as intended, requires control during limited hours or should be revised before construction. Daylight calculation versus electric-light photometric plan Daylight and electric-light studies answer related but different questions. Daylight calculation Electric-light photometric plan Models sun and sky conditions Models selected luminaires using photometric data Changes with date, time and orientation Changes with fixture type, output, optic and placement Evaluates windows, glazing and skylights Evaluates fixture spacing, mounting and aiming Helps assess direct sun and shading Verifies foot-candles or lux and uniformity Supports daylight availability and glare decisions Supports lighting design, coordination and permit documentation Many projects benefit from both. Daylight analysis shows when natural light is useful or problematic. A professional photometric plan verifies that the electric-lighting system provides appropriate coverage when daylight is unavailable or intentionally controlled. If the project includes parking lots, exterior site lighting, warehouses, sports areas or permit-related illumination requirements, request professional photometric plan services separately