One sheet cannot serve every format
A specification written for a fine-pitch indoor wall does not transfer to an outdoor billboard or a transparent facade panel. The physical construction differs, and that difference propagates through nearly every line of the sheet. Copying entries between formats produces a document that looks complete and describes nothing buildable.
The format decision therefore comes first. Chip-on-board modules protect the LEDs behind a surface layer and suit close viewing. Surface-mount modules expose individual packages and suit larger pitches. Flexible and transparent variants change the substrate, the cabinet frame and the service method. Each choice rewrites the constraints that follow.
Brightness follows the environment
Brightness is set by where the wall has to be read, not by a preference for a bigger number. An outdoor wall facing direct sun needs far more output than an indoor lobby wall. Specifying outdoor brightness for an indoor room wastes power and creates glare that viewers experience as discomfort.
Brightness also interacts with the content and the surface. A glossy face under strong ambient light shows reflections that no brightness figure fixes. The entry belongs next to a note about the light environment, the viewing hours and the surface treatment, otherwise the number is unverifiable in practice.
Pitch, scan and driver choices move together
Pixel pitch sets the resolution for a given size, and it also constrains the driver architecture. A fine pitch packs more LEDs into each area, which changes the scan pattern, the number of driver channels and the heat produced per square metre. Treating pitch as a standalone line hides those consequences.
Refresh behaviour and camera compatibility follow the same chain. A wall that will appear on video needs a refresh rate high enough to avoid banding, and that requirement pushes the driver and receiver selection. Writing the camera use case into the sheet early prevents a late upgrade that costs more than the original choice.
Thermal load and power sizing
Every entry that raises output or density raises heat. Brightness, pitch and continuous run time combine into a thermal load that the cabinet design and the room ventilation must handle. A specification that names power per square metre without a duty cycle leaves the installer guessing.
Power sizing follows the same logic. The supply must cover peak demand with margin, and the distribution must match how the wall is switched and protected. Ingress protection belongs here too: outdoor cabinets are rated for water and dust under a two-digit scheme such as IEC 60529, and that rating changes the housing, the seals and the thermal path.
Entries that change as a set
Read the sheet in groups. Format with substrate and service method. Pitch with resolution, scan, driver and heat. Brightness with environment, content and surface. Power with duty cycle, protection and distribution. When a group is consistent, the document describes a product that can be built.
The test is simple: change one entry and ask which others must follow. If the answer is none, the sheet is probably too vague to price. If the answer is several, the specification is doing its job by showing the real dependencies before they become variations on an invoice.
Where two suppliers read one entry differently
Two suppliers can quote the same entry and mean different things. A brightness figure may be peak or average, measured at the module or across the wall. A warranty period may cover parts only, or parts and labour. A pitch may describe the module, or the effective spacing once cabinets are joined.
Ask for the definition beside the number. A sheet that states how each figure is measured can be compared; one that leaves the method implicit forces you to assume the most favourable reading, which is rarely the one written into the contract. The definition is often more valuable than the figure it describes.
Reusing an indoor sheet outdoors
A buyer copied an indoor specification to an outdoor totem. The pitch was fine, but brightness was far too low for daylight and the power budget omitted the extra drive current, so the wall dimmed under load.
Two suppliers, one entry, two readings
One supplier read 'pixel pitch' as centre-to-centre including the bezel, the other as active pixel only. The two quotes described different real resolutions for the same written value.
Putting this into practice: specification
- Fix the format before any other entry Indoor, semi-outdoor and outdoor are different problems. Choose the format first, because every later line on the sheet depends on it.
- Let brightness follow the environment Specify nits against ambient light and viewing distance, not a single headline number. A value chosen for a dark hall is wrong for a sunlit window.
- Let pitch and power follow the viewing task Pitch follows the closest viewer; thermal load and power sizing follow from pitch, brightness and cabinet count as a set. Check that the entries constrain each other.
Assumptions to check on specification
“One specification sheet fits every format.” — Indoor, semi-outdoor and outdoor change brightness, sealing, thermal and power together. A sheet whose lines do not constrain each other is a wish list, not a specification.
“Pixel pitch only affects resolution.” — Pitch also drives cabinet count, power, thermal load and sometimes the driver and scan strategy. Changing it moves several other entries at once.
What to carry forward on specification
An LED display specification is a chain of dependent entries. Fix the format first, then let brightness follow the environment, pitch follow the viewing task, and thermal and power follow the combination. A sheet whose lines do not constrain each other is not a specification; it is a wish list that every supplier will interpret differently.