Screens and projection · SERVICE · REV 2026-10-06
LED screens
An LED pixel is seen when its angle at the eye is larger than acuity can blend. The one-arcminute estimate — 1/60 of a degree — puts distance in metres near 3.4 times pitch in millimetres. That is a geometric limit for when a pixel shows, not a brand rule and not a comfortable distance for reading text.
Definition
Pitch is centre to centre. Content changes what you need: scenic video tolerates a coarser pitch than small text or a drawing at the same distance. Luminance, in nits, is a figure from the panel sheet at the stated drive and content — full white is not a meeting picture. This page publishes no nit value as a BoxTech O2mea specification. Indoor and outdoor are different problems because daylight is far above hall lighting, and an outdoor panel in a dark room glares and heats.
Service decides whether the wall is possible: removal from the front if there is no void behind, or a rear catwalk of a safe width if service is from behind. Power and heat follow content and duty from the manufacturer sheet, not from a claimed wattage. Cooling sees the heat in the hall and in the rear void. The processor and the screen retire together if spares are not named.
When is this service needed?
The viewer is close and the text is fine
An exhibition stand or a shallow hall. Pitch is chosen for the distance, not for a catalogue photo taken from far away.
Daylight or a dark hall
The environment changes the luminance required. The figure comes from the sheet for that environment, not from this page.
No void behind the wall
Front service is an architectural condition. A rear-service panel on a solid wall cannot be maintained.
The content is wide video from far away
A pitch finer than the eye’s limit is cost and heat with no readable difference. The arcminute estimate stops the bidding.
Where it is used
Halls and lectures
Behind the talker or beside them. Sightline and glare on the face constrain the height, not the render.
Theatres
A backdrop or a side screen. Luminance must not kill face light. Service must not cross the rigging path.
Outdoor and facades
Sun, water, and a higher panel temperature. An outdoor sheet is not installed indoors as an upgrade.
Exhibition booths
The aisle distance is short. A pitch that looks smooth in the render may show a grid from two metres.
Parts of the solution
Modules and pitch
Pitch comes from the series sheet. Mixing pitches on one wall is a content decision, not an accidental replacement.
Processor and signal
Input resolution, latency, and genlock with a camera if there is one. A wall with no known processor is not handed over.
The service path
Front or rear, with tool space and module weight. The rear catwalk is a working width, not a crack.
Power and distribution
From the consumption sheet at the named content: white, or typical video. The electrical engineer chooses which figure to design to and writes it down.
Cooling
Heat is about equal to the power consumed in the room. A closed rear void with no air returns the failure.
Engineering considerations
One-arcminute geometry
The tangent of 1/60 of a degree is small, so distance in metres is about 3.4 times pitch in millimetres. An acuity estimate, not a product rule.
Content moves the estimate
Small text wants a longer distance or a finer pitch than scenic video. The arcminute limit is not a comfortable reading distance.
Indoor is not outdoor
A daylight-bright panel in a hall glares and raises the load. The sheet is read for the actual environment.
No nit value on this page
Any luminance figure is copied from the manufacturer sheet with its drive conditions. It is not a BoxTech O2mea specification.
Sightline
A head in front of the viewer can hide the bottom of the screen. A larger wall does not repair a wrong seating section.
Materials
The module face
Mask, durability, and cleaning come from the product sheet. Replacement is the same pitch so a line does not appear.
The structure
The wall’s weight is a load on the wall or on a rated hang. Uncalculated scenery steel is not a support.
Cables
Signal and power are separate, on a route that is not crushed when a module is removed. Service reopens that route every time.
Related systems
Lighting
The talker’s face and the screen’s light fight if luminance is arbitrary. Coordinate with the lighting page.
Picture and sound
Picture delay against sound is checked in conferences and broadcast. The wall is not instant in time.
Cooling plant
Heat load comes from real power, not from a decor guess. It is handed to the mechanical engineer in writing.
A projector as the alternative
When the distance is long, the content is coarse, and the light is controlled, projection may be enough. The comparison is geometric, not fashion.
Design sequence
- 01
Name the nearest viewer, the farthest viewer, and the content: text, a face, or a general image.
- 02
Estimate the pixel-visibility limit at 3.4 m per millimetre of pitch, then increase distance or refine pitch for text. The estimate is not a brand rule.
- 03
Choose luminance for the environment from the manufacturer sheet. Do not copy a nit value from this page, because it has none.
- 04
Fix service: front with no void, or rear with a catwalk. Draw the path before the facade is frozen.
- 05
Turn the power sheet at the expected content into electrical and heat load and hand it to engineering.
Delivery sequence
- 01
The structure is built straight enough for the joints between modules. A bow is a permanent bright line.
- 02
Modules are installed from one pitch batch. A random replacement shows as a patch.
- 03
Power and signal routes are separated, and each module stays serviceable without dismantling the whole wall.
- 04
Current is measured on white and on the expected show content. The difference is written down.
- 05
Cooling is checked after an hour of operation, not only at startup.
Testing
The real distance
Read text or a picture from the farthest and nearest seats. The arcminute estimate is a hypothesis and the eye in the seat is a first judgement.
Glare
From the side seats and on the talker’s face. Too much luminance is a defect, not quality.
Service
Remove a module and refit it in the agreed operating time. A wall that cannot be opened is not handed over as maintainable.
Commissioning
Reference content
Text at the smallest expected size and a typical video. Handover on a logo alone does not prove the pitch.
The power sheet
The figure used in design roughly matches the measurement, or the gap is explained. No watt value comes from this page.
Processor and spares
The file revision and a spare module of the same pitch are in the handover. Without a spare the wall stops at the first failure.
Maintenance
Face cleaning
By the method on the manufacturer sheet. A random solvent dulls the mask and changes the look, not the pitch.
Module replacement
From the batch, or with colour calibration. A patch of different luminance is seen sooner than a dead pixel.
A heat check
Filters and fans in the rear void. Rising temperature cuts life before the content is blamed.
Common mistakes
The finest pitch in the catalogue
The viewer is beyond the eye’s limit. You paid for resolution that is not read and heat that is not required.
An invented nit value
Copying a luminance figure from a page or from another project. Environment and content are on this panel’s sheet.
A wall with no service
Sticking rear-service modules to a solid wall. The first failure demolishes the finish.
Full white as the only load
Or ignoring it completely. The electrical engineer needs the figure that will actually occur, named from the sheet.
Short comparison
The comparison is a way to choose a path. It is not a product recommendation and it is not a code.
| Path | Fits when | Weakens when |
|---|---|---|
| A finer pitch | The viewer is close or the text is small, and the heat and cost are acceptable. | When the distance is longer than the one-arcminute limit. The eye does not buy the difference. |
| A coarser pitch | A general image from far away, or a limited budget and heat load. | When text breaks up from a near seat. The saving shows as a grid. |
| A projector | The distance is long, the light is controlled, and maintenance is acceptable as lamp or laser. | When hall light is high or throw is unavailable. A self-lit screen is then more honest. |
Discussion ranges
Any number here is a preliminary discussion range from practice or a named reference. Replace it with the project criterion, laboratory data, and on-site measurement.
| Item | What is discussed | Limit of this page |
|---|---|---|
| 3.4 m per mm of pitch | The approximate distance at which a pixel subtends one arcminute, from the tangent of 1/60 of a degree. | An acuity estimate, not a brand rule and not a comfortable text distance. Content, contrast, and the viewer’s acuity move the figure. The calculator on the site is a first guess. |
| The pitch itself | Centre-to-centre pixel distance, from the panel series sheet. | No pitch is imposed by this page. Choosing one without a viewing distance and a content type is incomplete. |
| Luminance in nits | A manufacturer-sheet value at a named drive and content. White is not typical video. | No nit value on this page may be copied as a BoxTech O2mea specification. An indoor room is not designed with an outdoor figure. |
| Thermal power | The sheet’s consumption at the chosen content, which approximates the cooling load. | No watt value here. The electrical design names which column of the sheet it used. Site measurement corrects the estimate. |
What this page does not claim
No fire classification, absorption coefficient, sound pressure level, or legal capacity on this page may be copied into a quotation. Those values come from a product test report, a measurement, or the local code adopted for the project.
Questions designers and owners ask
How do I get distance from pitch?
As an estimate: metres ≈ 3.4 × pitch in millimetres for the limit at which a pixel shows at one arcminute. For text, sit closer or refine the pitch. It is not a manufacturer rule.
Why will you not give a nit figure?
Because luminance comes from the panel sheet at the content and the environment. A figure from this page would be copied wrongly as a specification.
Is the brighter screen better in a theatre?
Not automatically. It can glare the audience, kill face light, and raise heat. Luminance matches the task.
Front service or rear?
Front if there is no catwalk. Rear if the catwalk exists and is safe. The panel is not chosen and the wall then discovered to be solid.
Does DISCAS apply to LED?
DISCAS is a procedure for image size and viewing task. This page does not perform it. Pitch is an extra question about whether the pixel shows inside that size.
Technical sources
- The panel series sheet
Pitch, luminance at a named content, power, and service method. This page does not extract the figures.
- One-arcminute geometry
An angle of 1/60 of a degree gives about 3.4 m per millimetre of pitch. An acuity estimate, not a product standard.
- AVIXA DISCAS
The image-size procedure from the viewing task. This page does not perform the procedure and does not output a screen height.
Last editorial review: 2026-10-06. Review means the text was checked, not that a project was measured.
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