Descriptive lux spread ratios
A lux uniformity ratio note describes the relationship between the lowest, average and highest values in one reading set. It reports ratios only and does not judge a project or replace measured point notes.
Ratio note sequence
A clear ratio note keeps the reading set together, then separates descriptive spread from wider lighting interpretation.
- 1Name the reading set
State the room, zone, task plane or grid that produced the values.
- 2Confirm one condition
Keep switching, dimming, daylight and relevant furniture or equipment state consistent.
- 3Enter the three values
Take minimum, average and maximum from the same set.
- 4Read both spread views
Compare min-to-average ratio with max-min spread so ratio and absolute lux span stay visible.
- 5Link the point evidence
Keep labelled readings or a grid note nearby when location matters.
Application search intent fit
Keep uniformity-ratio searches on the relationship between measured values, not on project judgement.
| Search phrasing | Ratio note | Carry forward |
|---|---|---|
| Lux uniformity ratio calculator | Minimum lux divided by average lux for one reading set. | Point labels, plane name, reading layout and operating condition. |
| Minimum to average lux | Lowest point compared with the average of the same set. | Where the low point occurred and whether it is a task location. |
| Maximum to average lux | Highest point compared with the same average. | Whether a bright point comes from daylight, aiming, proximity or reflection. |
| Lux spread check | Maximum minus minimum shown as a descriptive lux span. | Grid notes, surface notes and fitting layout context. |
Input quality
The ratio is most useful when the three values come from the same reading set and operating condition.
| Note item | Strong entry | Weak entry |
|---|---|---|
| Minimum lux | Lowest value from the same measured set. | A low point borrowed from a different room or time. |
| Average lux | Arithmetic average for the same selected points. | An estimate from a separate room calculation. |
| Maximum lux | Highest value from the same measured set. | A bright point measured under a different daylight condition. |
| Reading set | Same plane, labels, switching state and daylight note. | Mixed planes, scenes or dates blended into one ratio. |
Reading the output
Each output describes one part of the spread. None of the outputs explains the physical cause by itself.
| Output | Technical meaning | Review item |
|---|---|---|
| Min-to-average ratio | Minimum lux divided by average lux. | Lower values indicate a wider gap between the low point and average. |
| Uniformity percentage | The same min-to-average relationship expressed as a percentage. | Read beside the actual minimum and average values. |
| Max-min spread | Maximum lux minus minimum lux. | Shows absolute lux span across the entered set. |
| Maximum-to-average ratio | Maximum lux divided by average lux. | Helps identify how far the bright point sits above the average. |
Separated questions
A ratio can describe spread without answering why the spread exists or how the space should be changed.
| Question | Why it remains separate | Better owner |
|---|---|---|
| Where are the weak points? | Ratios do not keep point locations visible. | Lux meter grid notes and labelled point notes. |
| What caused the spread? | Values can be affected by spacing, optics, surfaces, daylight and obstructions. | Layout, surface and luminaire notes. |
| Is the average lux enough? | A spread ratio does not decide the planning target. | Room, workplace or measured-average notes. |
| Did comfort change? | Lux ratios do not describe glare, reflections or source brightness. | Glare and visual-comfort notes. |
Ratios belong to one reading set
A uniformity ratio is only meaningful when minimum, average and maximum values come from the same set. A low point from a bench, an average from a room estimate and a high point from a sunlit floor do not describe one lighting condition.
For an Australian field note, name the room or zone, the assessed plane and the operating condition first. The ratio then becomes a compact description of spread inside that named evidence, rather than a loose number detached from the readings.
Minimum-to-average shows the low side
The min-to-average ratio compares the lowest value with the average. A value closer to 1.00 means the lowest point is close to the average. A lower value means the lowest point sits further below the average.
The actual minimum value still matters. A similar ratio can describe very different spaces if one set sits around low lux levels and another set sits much higher. Keep the lux values beside the ratio so the spread does not hide the light level.
Maximum-to-average shows the high side
The maximum-to-average ratio shows how far the brightest point sits above the average. A high value can come from a fitting directly above the sensor, daylight near a window, a reflective surface or a narrow beam.
That high point is not automatically a problem and not automatically helpful. It is a clue for the surrounding note: where the point sits, what was switched on, whether daylight was present and whether the sensor position represents a real task location.
Spread in lux keeps scale visible
Ratios can hide scale, so the max-min spread is shown in lux. A spread of 60 lx and a spread of 260 lx can feel very different in a task area even if ratios appear similar in another set.
Absolute spread also helps when comparing repeated readings over time. Cleaning, lamp ageing, obstruction changes, diffuser condition, furniture moves and daylight state can all change the span between low and high points.
Point labels explain the number
Ratios do not say where the low or high value happened. Point labels do. A low point at a room edge, under a shelf, between fittings or beside a tall object means something different from a low point on the main task surface.
Keep P1, P2 or grid labels with the original readings. The ratio is then easy to read beside the drawing, room note or table that shows where the spread occurred.
Operating condition can move every ratio
Switching state, dimming, daylight, blind position, open doors, temporary equipment and surface changes can all alter minimum, average and maximum values. A ratio from one condition should not be mixed with values from another condition.
When both daylight and artificial-light-only states matter, note them as separate sets. Each set can then have its own ratio and lux spread without blurring the evidence.
Descriptive ratios stay modest
The result reports relationships between values. It does not decide whether a room, workplace, warehouse aisle, retail display, home office or shared area has the right lighting arrangement.
A fuller lighting note still needs the measured points, task plane, average level, surfaces, luminaire layout, daylight condition, glare observations and any project requirement that applies. The ratio is useful because it describes spread without pretending to settle those matters.
Average quality affects the ratio
The average value should come from the same points that produced the minimum and maximum. A quick average from only the brightest points will make the low side look weaker than it really is, while an average that includes unrelated edge points can make a main task area look less even than the actual work surface.
Keep the count of readings and the selected point set beside the ratio. A later reader can then tell whether the note describes a compact task area, a whole room, a rack aisle, a display wall or a circulation path.