UFO vs Linear High Bay: Beam Patterns for Uniform Lighting – Hyperlite

Eliminate shadows and hot spots in your facility. This guide walks through how UFO and linear high bay beam patterns actually behave in the field, and how to use each style to achieve uniform, code-ready illumination in open floors and racked aisles.

Quick Reference for Decision-Makers

For those needing a fast, high-level overview, here are the key takeaways:

Application	Recommended Fixture	Key Rationale
Open Areas (Workshops, Gyms, Bulk Storage)	UFO High Bay (or Symmetric Linear)	Simple grid layout, flexible for future changes, and excellent horizontal uniformity when spaced correctly (S/MH ratio ≈ 1.0–1.5).
Racked Aisles (Warehouses, Distribution Centers)	Linear High Bay with Aisle Optics	Delivers significantly more vertical light onto rack faces, improving picking accuracy. The beam is shaped to fit the aisle, reducing wasted light.
Mixed-Use Spaces	Hybrid Approach	Use a UFO grid for open areas and dedicated linear aisle fixtures over racks. Zone controls separately for maximum energy savings.
Core Principle	Model First, Then Buy	Always use manufacturer-provided IES files in software like AGi32 to verify your layout before purchasing. Do not rely on lm/W alone.
Verification	Measure On-Site	Post-installation, conduct spot measurements of horizontal and vertical illuminance to ensure the design matches reality.

1. Beam Pattern Basics: What “Uniformity” Really Means

Before choosing UFO vs. linear, it helps to define what “good” looks like.

1.1 Key metrics for uniformity

For high‑bay lighting, designers care about more than raw lumens:

Average illuminance (Eavg) on the work plane, typically in lux or foot‑candles.
Minimum illuminance (Emin) so you do not have dark pockets.
Uniformity ratio (Emin/Eavg) – often written as “min/avg.”
Vertical illuminance on rack faces, machinery, and walls.

From practical warehouse and industrial work:

For picking/packing and detailed work, aim for maintained Emin/Eavg ≥ 0.40.
For bulk storage and open floor with less critical tasks, ≥ 0.25 is usually acceptable.

These are not hard code values; they are practical targets derived from typical recommendations in documents like ANSI/IES RP‑7 – Lighting Industrial Facilities, which provides application‑based illuminance and uniformity guidance for industrial spaces.

1.2 How beam shape drives uniformity

Think of the beam as a footprint on the floor:

UFO high bays typically have round beams (90–120°).
Linear high bays use elongated optics, often symmetric (e.g., 110°) for open areas or asymmetric “aisle” beams (e.g., 60°×120°) for racked spaces.

A simple rule of thumb for the diameter of a round beam is:

Beam diameter ≈ 2 × mounting height × tan(θ/2)

where θ is the beam angle.

Designers then use IES photometric files (.ies) following IES LM‑63 to simulate this distribution in software like AGi32 and validate uniformity.

UFO LED High Bay shop lights illuminating a high‑ceiling pole‑barn workshop at night

2. UFO vs. Linear: How the Beam Patterns Differ

This section focuses on what actually changes when you switch from circular to linear beams.

2.1 Open‑floor layouts (no racks)

In open spaces – fabrication floors, sports barns, large garages – the main question is, “How many fixtures do I need, and how far apart can I space them without hot spots?”

From field layouts and IES‑based calculations:

UFO high bays (90–120°) work well at 20–30 ft (6–9 m) mounting heights.
A spacing‑to‑mounting‑height ratio (S/MH) of ~1.0–1.5 gives good overlap.
Linear high bays with wide optics behave similarly; the longer body just changes where the light goes first.

Independent LM‑79/IES photometry comparisons support this. Tests on UFO and linear high bays with the same lumen package often show very similar horizontal uniformity (U0/U1 ratios) in open areas. According to one analysis of warehouse layouts, the real difference emerged in vertical illumination, not in the aggregate horizontal uniformity score.

Implication: For an open shop or arena, UFO vs. wide‑beam linear is largely a mechanical and aesthetic decision. Both can meet the same uniformity targets when you respect S/MH ~1–1.5 and validate with IES files.

2.2 Racked aisles and narrow corridors

The story changes once you introduce tall racks.

With UFOs, a round beam tends to send a lot of light into the top of the racks and across aisles.
Linear aisle optics compress the beam across the aisle and stretch it along the aisle, delivering more light where pickers actually work.

Photometric studies referenced in a manufacturer analysis by ACE LED Light found that tilting linear aisle fixtures 10–15° toward the pick face could increase vertical illuminance by roughly 20–30% with the same wattage. That kind of gain on rack faces is hard to achieve with UFOs without adding wattage or more fixtures. (Note: This percentage is based on a vendor case study and should be independently verified with photometric modeling for your specific project.)

Implication: For dense racking and order‑picking, linear aisle optics have a clear vertical‑light advantage, especially once you start fine‑tuning the aiming.

2.3 Glare and visual comfort

Glare is driven by luminous area, cutoff, and background brightness, not just fixture shape. However, there are some typical patterns:

A compact UFO with a clear lens can look like a bright “point” at higher nit levels.
A diffused linear presents a larger, softer luminous area that can feel more comfortable at the same lumen level.

The GSA LED and Controls Guidance explicitly calls out glare management and recommends high‑efficacy fixtures that still control brightness in high‑visibility industrial and commercial settings.

Pro Tip – Expert Warning: A common assumption is that linear optics always reduce waste light and glare. Field experience and analyses such as the warehouse guidance from Maes Lighting (a lighting vendor) show the opposite when narrow beams are misapplied. Very tight linear distributions at low mounting heights can create harsh contrast and elevated discomfort glare, especially when the fixture is directly in view. A well‑shielded UFO with a reflector or lens at the same wattage sometimes delivers more comfortable lighting because the cutoff is more controlled.

3. Comparison Framework: UFO vs. Linear Beam Patterns

Use the following table as a quick decision guide when the goal is uniformity.

3.1 Pros, trade‑offs, and ideal use‑cases

Factor	UFO High Bay (Round Beam)	Linear High Bay (Symmetric / Aisle Beam)
Typical beam	90–120° symmetric	110° symmetric; 60×120° or 60×90° aisle
Best for	Open floors, arenas, barns, shops	Racked aisles, long process lines
Open‑area uniformity	Very good with S/MH ≈ 1.0–1.5	Comparable with wide optics
Vertical illuminance on racks	Moderate; often needs more wattage or density	Strong, especially with 10–15° tilt (verify with modeling)
Glare control	Can be high‑brightness points; improve with reflectors/lenses	Softer appearance; but narrow beams can create harsh contrast
Layout risk	Simple grid; easy to match existing points	More sensitive to aiming and rack changes
Maintenance impact	Compact shape, fewer surfaces to collect dust	Long optics and lenses can get dirty faster, impacting uniformity
Controls zoning	Easy per‑fixture zoning; ideal for granular occupancy control	Often wired in rows; aisle‑level zoning is common

3.2 Myth‑busting: “UFOs are always bad for aisles”

A persistent myth is that UFOs are inherently the wrong choice for aisles.

Field layouts and retrofit audits show a more nuanced picture:

A medium‑beam UFO combined with a tilt bracket or wire‑guard aiming system can outperform a mis‑aimed linear aisle fixture when racks move or aisle widths change.
Because UFO grids often match previous HID mounting points, contractors tend to stick closer to the photometric design, avoiding the drift that happens when linear rows are shifted during construction.

Analyses similar to those cited in a vendor guide by LEDMyPlace show that realized performance in the field frequently depends more on installation quality than on fixture shape alone.

Takeaway: Linear aisle optics usually win for long, fixed rack runs, but a well‑aimed UFO grid is perfectly valid and can be more forgiving when layouts change over time.

4. Spacing, Mounting Height, and Beam Geometry

Once you understand the beams, the next lever is geometry: how high, how far apart, and how many.

4.1 Practical S/MH rules that actually work

From repeated warehouse and shop layouts, the following spacing‑to‑mounting‑height ratios are reliable starting points:

Open floor with UFOs or wide‑beam linears:
- S/MH ≈ 1.0–1.5 both ways.
- Example: 25 ft mounting height → 25–35 ft grid spacing.
Narrow racked aisles with aisle optics:
- Along the aisle: S/MH ≈ 0.8–1.2.
- Across aisles (between rows): S/MH ≈ 1.5–2.0.

These ranges reflect layouts that consistently achieve maintained Emin/Eavg ≥ 0.4 in picking zones when modeled with realistic reflectances and verified using AGi32.

4.2 Using the beam diameter formula

For UFOs, combine S/MH with the beam diameter estimate to sanity‑check your layout.

Example – 25 ft mounting height, 90° UFO beam

θ = 90° → tan(θ/2) = tan(45°) ≈ 1.
Beam diameter ≈ 2 × 25 × 1 = 50 ft.
If you set S/MH = 1.2 → spacing ≈ 30 ft.

This means each beam overlaps significantly with its neighbors, which is what you want to avoid scalloping.

Example – 25 ft mounting height, 110° beam

θ = 110° → tan(55°) ≈ 1.43.
Beam diameter ≈ 2 × 25 × 1.43 ≈ 71.5 ft.
With 30 ft spacing, beams overlap heavily. That can be great for uniformity but may push more light onto upper walls and ceiling.

Practical implication: At 20–30 ft, beam angles between 90° and 120° are usually ideal for UFOs and symmetric linear optics. Much wider distributions (>120°) tend to waste light upward and increase glare; much narrower beams make hot spots unless you reduce spacing.

4.3 Reflectance and real‑world surprises

One big reason modeled and actual uniformity diverge is surface reflectance:

Dark ceilings and racks (10–20% reflectance) soak up uplight.
Light ceilings and high‑reflectance walls (60–80%) recycle light back into the space.

Guidance in documents like NREL’s high‑performance building best practices manual highlights how surface finishes are a key lever in achieving target illuminance with less connected load.

Pro Tip: Do not just plug 50% reflectance into your lighting software because “that’s what everyone does.” For older, non‑painted warehouses, 20–30% is more realistic. Over‑estimating reflectance is a common reason that “on‑paper” layouts fail to hit measured lux targets.

5. Vertical Illuminance on Racks vs. Flat Floors

Uniformity is often measured on a horizontal plane, but in racked facilities, vertical light is what drives productivity and error rates.

5.1 Why vertical illuminance matters

According to industrial lighting guidance such as ANSI/IES RP‑7, high‑activity storage and order‑picking areas need higher and more uniform illuminance, including on vertical faces. In practice:

Clear labeling and barcodes reduce mis‑picks.
Better visibility deep into racks reduces the need for handheld flashlights and re‑checks.

Warehouse audit experience shows that improving vertical illuminance on pick faces can measurably reduce picking errors, even when average horizontal lux changes very little. While specific gains vary, some manufacturer case studies suggest a 20–30% improvement in vertical light can be a key driver of these operational benefits. Independent verification through a pilot installation or detailed photometric modeling is the best way to confirm the impact in your facility.

5.2 UFO vs. linear for vertical targets

With UFOs, you can improve vertical light by:
- Slightly tightening beam angle (e.g., 90° instead of 120°) to send more light downward.
- Lowering mounting height within code and clearance limits to increase wall incidence.
- Tilting fixtures toward the rack face where hardware allows.
With linear aisle optics, you can:
- Use asymmetric beams that “throw” light at the pick face.
- Rotate fixtures 10–15° toward the racks, an approach that photometric studies (such as the previously mentioned ACE LED Light manufacturer analysis) show can boost vertical lux significantly.

Expert Insight: Standard LM‑79 reports quantify total lumens and distribution, but the combination of LM‑79 IES files plus a good vertical‑plane calculation in software is what ultimately predicts how easy it is to read a label 20 ft up. Use that workflow instead of judging fixtures by lumens per watt alone.

6. Controls, Rebates, and “kWh per Maintained Lux”

Uniformity and energy performance are linked. A distribution that puts light where it is needed reduces the number of fixtures and the time they must be on.

6.1 Why controls design differs for UFO vs. linear

From field projects and guidance such as the DOE FEMP solid‑state lighting resources:

Per‑fixture control on UFO grids:
- Small, relatively independent beams.
- Ideal for sensor‑on‑every‑fixture strategies in open areas and mixed‑use shops.
- Often deliver higher kWh savings because fixtures near doors, windows, or occasional‑use zones can dim or turn off while others stay on for safety.
Row‑based control on linear systems:
- Common to group sensors by aisle or row.
- Great for long, consistently used aisles, but sometimes forced to stay on for safety or alignment reasons.

Analyses similar to those summarized in the DOE Interior Lighting Campaign final report show that projects combining high‑efficacy luminaires with granular occupancy and daylight control achieved 40–60% lighting energy savings relative to older HID or fluorescent baselines.

6.2 Rebate requirements and documentation

For projects seeking utility rebates, the DesignLights Consortium Qualified Products List is usually the gatekeeper:

Many programs explicitly require DLC Standard or Premium listing for high bays.
DLC listing is based on verified LM‑79 photometry, LM‑80 chip testing, and TM‑21 lifetime projections.

Similarly, safety and inspection compliance often depend on listings in databases like UL Product iQ or Intertek’s ETL directory for luminaire safety standards such as UL 1598 and UL 8750.

Best practice: When comparing UFO vs. linear options, always request:

LM‑79 reports and IES files for each wattage/optic.
LM‑80 and TM‑21 documentation supporting lifetime claims.
DLC QPL links and UL/ETL file numbers.

That documentation allows you to compare kWh per maintained lux on task planes, not just catalog efficacy. In many racked warehouses, well‑aimed linear aisle optics show 10–20% lower kWh per maintained lux than equivalent UFO grids, even when their nominal lm/W is similar.

7. Practical Layout Recipes: Open Floor vs. Aisles

This section gives starting templates that contractors and facility managers can adapt using IES‑based calculators.

7.1 Open warehouse or shop (20–24 ft ceiling)

Scenario: 80 ft × 120 ft open warehouse, 22 ft mounting height, light‑colored ceiling (70% reflectance), medium task detail.

Target:

Average 30–40 fc (320–430 lux) on the floor.
Emin/Eavg ≥ 0.35–0.40.

Starting layout (UFO or wide‑beam linear):

Use a grid of 4 × 6 = 24 fixtures.
Spacing along 120 ft dimension ≈ 24 ft; along 80 ft dimension ≈ 20 ft.
S/MH ≈ 1.0–1.1 → good overlap.

With high‑efficacy fixtures (~140–150 lm/W) and realistic reflectances, AGi32 layouts for similar spaces show achieved uniformity around 0.4–0.45 with comfortable glare, especially when using diffusers or reflectors.

For additional safety considerations and circulation path emphasis, pair this with the guidance in Designing a High Bay Layout for Warehouse Safety.

7.2 Narrow racked aisle (30–36 ft ceiling)

Scenario: 200 ft long aisles, 10 ft wide, 34 ft mounting height, racks up to 28 ft.

Target:

Average 25–30 fc (270–320 lux) on floor.
Good vertical illuminance on rack faces, especially from 3–20 ft.

Starting layout (linear aisle optics):

Mount fixtures centered over the aisle.
Along the aisle: S/MH ≈ 0.9–1.0 → ~30–34 ft spacing.
Rotate each fixture 10–15° toward the primary pick face.

AGi32 studies and application notes, like those from the previously cited ACE LED Light analysis, show that this combination can significantly boost vertical illuminance on pick faces while maintaining acceptable floor uniformity. Independent modeling is crucial to confirm results for your specific geometry.

7.3 Flexible multi‑use shop (mixed open + localized racks)

When a space includes both open bays and partial racking – for example, a vehicle maintenance shop with parts shelving on one side – a hybrid approach often works best:

Use a UFO grid for the main open floor using S/MH ≈ 1.0–1.3.
Add short rows of linear aisle fixtures only where racks are dense and tall.
Put separate 0–10 V zones or sensor groups on the rack zones so those lights dim or switch off when the area is idle.

For fine‑tuning glare and comfort, pair these tactics with the strategies in A Specifier’s Guide to Low‑UGR High Bay Lighting.

8. Step‑by‑Step Checklist: Choosing UFO vs. Linear for Uniformity

Use this checklist before purchasing or specifying high bays.

Define the primary task areas.
- Open floor, racked aisles, or both?
- Critical tasks (inspection, picking) vs. basic storage.
Set target illuminance and uniformity.
- Use ANSI/IES RP‑7 ranges and your safety or process requirements.
- Translate to maintained Emin/Eavg targets (0.25–0.40+ depending on area).
Select candidate distributions.
- Open floor → UFO or symmetric linear, 90–120°.
- Long aisles → Linear aisle optics, possibly hybrid with UFOs for open zones.
Apply S/MH heuristics.
- Open: S/MH ~1.0–1.5.
- Aisles: along S/MH ~0.8–1.2; across S/MH ~1.5–2.0.
Model with LM‑79 IES files.
- Import manufacturer IES files (LM‑79 compliant) into AGi32 or similar.
- Use realistic reflectances (20–80%) and rack geometries.
Evaluate both horizontal and vertical illuminance.
- Check metrics on floor and on rack faces.
- Watch for excessive contrast or glare.
Optimize with tilt and optics before adding fixtures.
- Try 10–15° tilt for linear aisle fixtures.
- Consider narrower beams or reflectors for UFOs at high mounting heights.
Overlay controls and rebate requirements.
- Determine where per‑fixture sensors (UFO grids) or aisle‑based zones (linear) make more sense.
- Confirm DLC, LM‑79/LM‑80/TM‑21, and UL/ETL documentation for rebate and code compliance.
Document the layout.
- Export calculation grids, iso‑lux plots, and compliance notes.
- Keep these with submittals and as‑built documentation.
Plan for On-Site Acceptance Testing.
- Define key measurement points and acceptance criteria (see next section).
- Include this step in the project scope to ensure the final installation meets the design intent.

9. On-Site Verification and Acceptance Testing

A photometric model is a prediction; on-site measurement is the proof. To prevent a gap between design and reality, a mandatory commissioning step is to verify the installed performance.

9.1 Recommended Acceptance Procedure

Establish a Measurement Grid: After installation is complete and all fixtures are operational, create a grid of test points. A common practice is a 1m x 1m (or 3ft x 3ft) grid on the floor in critical areas. For vertical illuminance, define points on the rack face (e.g., at 1m, 2m, and 4m heights).
Measure Illuminance: Using a calibrated lux or foot-candle meter, take readings at each grid point.
- For horizontal illuminance, place the meter flat on the work plane (typically the floor).
- For vertical illuminance, hold the meter vertically, facing outward from the rack face.
Compare to Design: Compare the measured values (especially the average and minimum) against the values predicted in your photometric software (AGi32, etc.) and the project targets.

9.2 Sample Acceptance Log Template

Use a standardized table to document findings. This creates a clear record for project sign-off and troubleshooting.

Point ID	Location Description	Target (lux)	Measured Horizontal (lux)	Measured Vertical (lux)	Pass/Fail	Notes
A-01	Aisle 1, Bay 3, Floor	300 avg	315	N/A	Pass
A-02	Aisle 1, Bay 10, Floor	300 avg	240	N/A	Fail	Dark spot; check fixture above.
V-01	Aisle 1, Bay 3, 1.5m H	150 min	N/A	180	Pass
V-02	Aisle 1, Bay 10, 1.5m H	150 min	N/A	110	Fail	Low vertical light; check fixture aim.
C-05	Open Area, Center	400 avg	425	N/A	Pass

This process is vital for YMYL (Your Money or Your Life) applications where safety and task performance are critical. It ensures that the specified design delivers real-world compliance and value.

For more detail on lumens selection and control zoning, see the Warehouse Lumens Guide for UFO High Bay Lights and How to Zone UFO High Bay Dimming Controls.

10. Wrapping Up: Matching Beam Pattern to Layout, Not Hype

When the goal is uniform illumination without dark spots, the question is not “Which form factor is better?” but “Which beam pattern and layout fit this geometry and task mix?”

Key takeaways:

In open areas, UFO and symmetric linear beams perform similarly for uniformity when S/MH ≈ 1.0–1.5 and reflectances are modeled correctly.
In racked aisles, linear aisle optics with 10–15° tilt usually deliver superior vertical illuminance on pick faces for the same wattage.
Glare and comfort depend on optics, cutoff, and luminous area; both UFO and linear designs can succeed or fail depending on execution.
Long‑term uniformity is influenced by dirt accumulation and maintenance – compact UFOs often hold performance better than intricate linear lenses.
Combining verified photometric data (LM‑79/LM‑80/TM‑21), DLC‑listed efficacy, and solid layout work in AGi32 or similar tools is far more important than fixture silhouette.

By treating UFO vs. linear as a question of beam pattern and geometry, and following the spacing and modeling practices outlined here, contractors and facility managers can deliver bright, uniform, rebate‑ready lighting that stays effective long after the project sign‑off.

Safety & Compliance Disclaimer
Lighting design and installation affect life safety, productivity, and regulatory compliance. This article provides general engineering and layout guidance only. It is not a substitute for a stamped lighting design, electrical engineering services, or professional advice. Always verify local building and electrical codes (including NFPA 70/NEC or local equivalents), consult qualified design professionals where required, and follow manufacturer installation instructions and all applicable safety standards. The final verification of performance must be conducted on-site.

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Achieving Uniformity: UFO vs. Linear Beam Patterns