Every outdoor LED quote arrives with a spec sheet. Pixel pitch, brightness in nits, cabinet size, IP rating, refresh rate. It looks complete.
It isn't. Here are the four numbers that decide whether the screen still looks good in year three, and exactly how to ask for them in writing.
1. Brightness measured where?
"7000 nits" on a datasheet is usually a laboratory measurement of a single module at peak white, at room temperature, at 100% power. On site you get: a hot afternoon, a 30% derating for thermal protection, and a viewing angle that is nothing like straight-on.
Ask instead: "What is the calibrated brightness after 30 minutes of continuous operation at 40°C ambient?" A supplier who knows their product will answer in a sentence. A trader will send you the same PDF again.
2. Scan rate, not just refresh rate
Refresh rate (3840Hz) tells you the screen won't band on camera. Scan rate tells you how long each LED row is actually lit — and therefore how much current you are paying for every hour the screen is on.
Ask: "What is the scan mode, and what is the measured power consumption per square metre at 70% brightness?" Then multiply by your electricity tariff and your operating hours. This is the number that shows up on your monthly bill; the nits number never does.
3. Cabinet tolerance
Two cabinets that are each "960×960mm" can differ by 1-2mm in the die-cast frame. On a single row you won't notice. On a 6×4 wall, those millimetres accumulate into a visible seam that runs from top to bottom — and no calibration fixes a physical gap.
Ask: "What is the cabinet-to-cabinet tolerance, and are the cabinets machined from the same die lot?" Reputable manufacturers machine frames on the same tooling precisely because of this.
4. Service access
Front-service screens are sold as a convenience. But front service usually means magnet-front modules, which means a module you can remove from the street side — convenient if the screen hangs over a road, awkward if you also want a tighter weather seal over ten years.
Ask: "If a module fails at height, how many people and how many minutes does a swap take from behind?" Rear service with walk-in access is slower to sell and faster to live with.
None of this is exotic. It is just rarely written down, because a spec sheet is a marketing document, not a purchase contract.
Disclosure: I work with MuenLED, a Shenzhen LED manufacturer. Our AS series outdoor cabinets are built around exactly these four questions — same 960×960mm die-cast platform across 4 / 5 / 6.67 / 8mm, rear service, IP65:
https://www.mlxled.com/product/as5-outdoor-led-display-boards-p5/
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