Can a GR value be converted into UGR?

There is no general conversion that makes the scores interchangeable. If a project requires another assessment, use the appropriate calculation method with the relevant geometry, photometry, observers and background conditions. Do not subtract, divide or apply a percentage conversion to an existing score.

What limitation of CIE 112 matters for sports?

The public scope of CIE 112-1994 restricts validity to viewing directions below eye level. Its result cannot automatically represent an athlete looking upward directly toward a source while tracking a ball. Critical sightlines need additional design review. The report also distinguishes glare near the lit area from spill-light effects beyond it.

Does a catalogue UGR claim guarantee the installed hall result?

No. CIE 117 describes tabular results based on reference values and standard conditions as well as the calculation method. Ask what the quoted figure represents and retain its assumptions. Assess the actual hall and required viewing conditions when project compliance depends on the installed layout.

What must stay fixed when comparing two glare calculations?

Use the same assessment method, geometry, observers, viewing directions, operating scene and relevant background assumptions. Identify the exact photometric file, optic and accessories for each proposed luminaire. Compare the required viewpoints and worst-case result, then confirm the layout still meets illumination and uniformity requirements.

Does changing UGR from 22 to 19 mean a proportional improvement?

No. These are example model results, not percentages of discomfort or a measured CPS comparison. Under unchanged assumptions they can support a comparison at the stated observer. They do not prove the whole venue complies or yield a GR equivalent. Check the full required observer schedule and design brief.

Can a high average lux value prove low glare?

No. Average illuminance describes light on a specified plane, whereas glare assessment depends on sources, their positions, the observer and the scene. Request both suitable illuminance calculations and the applicable glare assessment. A project case reporting lux does not establish a glare score unless that result and its conditions are actually published.

Can GR and UGR Values Be Compared Directly?

Q: Can GR and UGR values be compared directly?

No. GR and UGR are results from different glare assessment methods with different intended contexts and assumptions. A GR result of 45 and UGR result of 19 do not establish which installation is more comfortable. Identify the required method, applicable limit and complete calculation conditions before judging compliance.

2026-11-03

Contents

1. Different Methods Need Different Comparisons
2. Identify What Each Method Evaluates
3. Ask What the Catalogue Number Represents
4. Compare Proposals Under the Same Conditions
5. Use Glare Evidence With the Full Design Brief
6. Technical Sources

1.Different Methods Need Different Comparisons

A buyer receives two sports lighting proposals. One lists GR 45, and the other lists UGR 19. These assumed values illustrate a common procurement problem. The smaller number cannot identify the more comfortable installation because the results come from different glare models. Neither value is a percentage, and there is no general conversion that makes the two scores interchangeable.

Illustrative indoor basketball hall with athletes practicing below roof-mounted sports lighting — Assess the actual viewing conditions

A useful GR vs UGR comparison starts with the intended application, calculation method and viewing conditions. The CPS introduction to sports lighting glare metrics provides background. For a purchasing decision, request the applicable requirement and the underlying model rather than accepting a single catalogue number as proof of compliance.

2.Identify What Each Method Evaluates

CIE 112-1994 describes a glare evaluation system for outdoor sports and area lighting. Its public scope restricts validity to viewing directions below eye level and addresses glare within or close to the illuminated area. It does not assess spill-light effects beyond that area. A satisfactory GR calculation therefore cannot, by itself, resolve every upward ball-tracking view or a neighbouring property complaint.

CIE 117-1995 addresses discomfort glare in interior lighting. Its UGR method recognises observer position and viewing direction. The report also describes a tabular method based on reference conditions. This distinction matters when a supplier quotes a table value rather than a calculation for the proposed hall. Select the required assessment from the project specification and relevant application rules, not from the metric that gives the lowest number.

Check	Glare Rating: GR	Unified Glare Rating: UGR
Reference	GR: CIE 112-1994	UGR: CIE 117-1995
Intended context	Outdoor sports and area lighting	Discomfort glare in interior lighting
Example result	GR 45, assumed for teaching	UGR 19, assumed for teaching
Comparison rule	Compare with the applicable GR limit	Compare with the applicable UGR limit
Missing information	Observer positions, view directions and lit-area background	Observer positions, view directions and room conditions

3.Ask What the Catalogue Number Represents

A luminaire contributes to glare through its visible brightness, distribution and position in the scene. A room or pitch adds geometry and background conditions. A table of reference results is useful for screening, but it cannot establish every installed viewpoint. Ask whether the claim comes from a standard room table, a specific site model or a stated observer calculation. Retain the assumptions with the result.

The Dubhe 1000W floodlight has modular optics and mounting options. Its product description is not a GR or UGR approval for every layout. Obtain the exact optic and accessory configuration, with matching photometry. The guide to IES files after changing optics explains why a different lens or shield needs appropriate data rather than a reused distribution with a new label.

CPS Dubhe modular sports floodlight with multiple rectangular optical modules and adjustable bracket — Optics need matching calculation data

4.Compare Proposals Under the Same Conditions

For two comparable proposals, fix the venue geometry, mounting locations, observer coordinates, viewing directions and operating scene. Record the background assumptions and exact photometric files. The CPS calculation-plane guide explains why model height and direction need explicit definitions. A task-plane illuminance grid and an observer-based glare calculation answer different questions; keep both in the report.

Suppose two revisions of the same assumed hall model return UGR 22 and UGR 19 at one unchanged observer. That supports a comparison at that viewpoint under those assumptions. It does not prove the whole hall complies, establish a GR equivalent or show a proportional reduction in discomfort. Check the other required observers and retain minimum illuminance, uniformity and the specified vertical-light results when adjusting the layout.

5.Use Glare Evidence With the Full Design Brief

The CPS Grade III high-pole football project reports four-corner lighting on 18 m lifting poles and average illuminance above 550 lx after commissioning. Those figures describe an installed arrangement. They do not establish a published GR score or an indoor UGR equivalent. Treat case information as context, and ask separately for the glare evidence required by the next venue.

Before approval, check the method, limit, observer schedule, worst-case result and equipment revision in the lighting calculation report. Review critical player sightlines and any separate boundary-light requirements. If a design change reduces glare at the cost of coverage, revise the optics, aiming or positions and recalculate. The useful outcome is a documented layout that meets the venue’s full brief, not a comparison between unrelated numbers.