01 / Two quantities, two questions
Luminance describes light in a direction per projected area and is expressed in cd/m². Datasheets use “nits”; the CIE identifies that name as deprecated. Keep the original value and ask for the SI unit and measurement conditions.
CIE · luminance ↗CIE · cd/m² / nit ↗
Illuminance describes light reaching a surface, in lux (lm/m²). The CEM candela appendix describes illuminance and luminance measurements separately in sections 7.4 and 7.5. Record instrument, plane and direction; do not convert a lux reading into recommended display brightness without a substantiated model and conditions.
CEM · photometry, §§ 7.4–7.5 (PDF, English) ↗
To compare a brightness claim, ask for model code, picture mode, test pattern, setting, orientation, duration and stated thermal conditions. Separate the advertised maximum from what the manufacturer supports during the intended use. Ask the manufacturer which method was used to declare the value.
02 / Visit before choosing
- Incident light: record time, shade and exposure. A lux meter observes a plane; it does not measure image luminance.
- Shop-window glazing: identify layers, coatings and reflections from the street. Do not assume constant transmission.
- Display and content: compare the same artwork and setting. A datasheet maximum does not prove readability behind glass.
- Viewer: look straight on and from the side route. Record distance and the task they must understand.
Mark two viewing positions and photograph the surroundings from them, as well as the proposed display position. A phone photo can document geometry and reflection; automatic exposure prevents treating it as a luminance measurement. Record orientation, date, time, sky, shade and direct sun. Repeat in different conditions; one visit does not cover the whole year.
Identify the shop-window glazing with the site owner: pane count, coatings and any available specification. If you do not have the specification, record “request glass documentation.” Test the display behind the final shop-window glazing with actual artwork from both positions. If a reflection obscures the price, first try position, shading and composition; raising the setting alone does not establish that the message will be readable.
PLANNING EXAMPLE
03 / Teaching case: a shop window
Teaching assumption: a Seville shop wants to show a product offer from the pavement. The window is assumed to face west; the display would be indoors. Proposed points are P1, 2 m straight on, and P2, 4 m along the side route. Distances and orientation are assumed; replace them with site measurements.
On mobile, scroll the table to the right to read the complete record.
| Field | Example record |
|---|---|
| Task | Identify product and price; the QR code is secondary. |
| Glass | Request the site’s composition and coatings specification. |
| Test artwork | Same image, product and large price on both models; a second simplified version. |
| Proposed visits | 11:00, 17:00 and after dark; confirm for season, opening hours and actual sun. |
| Light and temperature | Plan measurements: agree instruments, points, conditions and recording with the integrator. |
| Current decision | Next step: test behind glass and document operating conditions before selecting the model and luminance. |
What would change the decision
If P1 works and P2 does not
Review angle, reflection and reading time. Repeat with a changed position or simplified artwork; do not approve the entire route.
If it fails only in direct sun
Record time and condition. Compare shading, installation and model options; an overcast test does not resolve this condition.
If it is uncomfortable at night
Ask how the setting is reduced and what happens after restart or sensor failure. Agree a test and check applicable local rules.
If A lists more nits than B
Keep the test consistent. Require conditions for both values, task readability and permitted usage; do not infer a winner from that number.
These branches are hypotheses for organizing a test, not observed outcomes. Before acceptance, agree who tests, which positions and content are used, when to repeat and how to record a failure. If the assembly receives direct sunlight, also request thermal evidence for the installation. An IP rating describes enclosure ingress protection; it does not by itself establish thermal performance, reflections or coastal resistance.
Spain: three places, different questions
AEMET data, 1981–2010 normals. These are historical averages for these stations, not a forecast, design extremes or temperatures inside a display. They do not represent the whole country.
Madrid, Retiro
- July · mean daily maximum
- 32.1 °C
- Mean annual precipitation
- 421 mm
Bilbao Aeropuerto
- July · mean daily maximum
- 25.4 °C
- Mean annual precipitation
- 1,134 mm
Sevilla Aeropuerto
- July · mean daily maximum
- 36.0 °C
- Mean annual precipitation
- 539 mm
During the site visit: in Seville, add a check of direct sunlight and the assembly’s thermal conditions; in Bilbao, plan maintenance access during rain and review actual water exposure; in Madrid, test summer conditions and seasonal operation. Also record the site’s orientation, shade and ventilation. At coastal sites, record proximity to the sea and exposure: these data do not measure salinity or establish any specific ingress or corrosion resistance.
Source: Agencia Estatal de Meteorología (AEMET). The integrator must substantiate conditions and protection for the exact model and installation.
05 / Prepare your site record
In the workshop, this note accompanies “Behind a shop window”; check the operating hours and number of displays for your project. At the procurement desk, add the site note to the shared project conditions without replacing the display count, comparison period or installation scope and record the specification and pending conditions under “Equipment,” testing behind the shop-window glazing under “Installation,” and artwork responsibility under “Content.” Mark “Included” only if the quote states it.
OFFICIAL MANUFACTURER WEBSITES
Official brand references
Browse categories and specifications on each manufacturer’s website. Links open in this tab. This is an independent selection with no commercial relationship with the brands.
Professional signage, shop windows and video walls
Samsung · official external website
Find categories and model documentation on the Spain portal. Verify usage, orientation and warranty for the exact code, not a category-level phrase.
Destination: Spanish ·
Sources and limits of this decision
Definitions: CIE e-ILV 17-21-050 and 17-21-086; units and measurement: CEM, candela appendix, §§ 7.4–7.5. Climate: AEMET, stations and period specified above. IP: IEC’s public explanation.
Collect site data and agree test positions, conditions and owners before choosing the model and accepting the installation.