Choosing Display Size and Format: Round, Bar-Type, Square and Standard

Format is chosen before size, because it decides what the enclosure can be, what tooling is required and which panels are actually available. A round or bar format changes the supply chain, the interface and the content layout; a standard or near-square format changes almost nothing. Deciding the format first avoids the common situation where the enclosure is designed around a panel that cannot be sourced in three years.

What the format decision changes

It changes tooling, supply and interface, not only appearance.

A standard 16:9 or 4:3 panel exists in a mature supply chain with several makers, published timing and a wide range of sizes. Square formats are available in a narrower but real range. Round and bar formats are either made to the format or produced by cutting a standard panel, and both routes add tooling, yield risk or wasted glass. The format also changes the interface, because unusual resolutions fall outside standard video modes and usually need a controller or custom timing.

The practical sequencing is to decide what the shape communicates about the product, then check whether that shape can be delivered by the cover glass and the content rather than by the panel.

Standard formats and their supply advantage

Standard ratios should be the default unless the shape is a product requirement.

Panels in the common ratios are available from multiple sources in overlapping size steps, which makes a second source and a later replacement realistic. Their timing tables are published, their interfaces are supported by most hosts, and their tooling is amortised across the whole market rather than across one programme. For most industrial equipment, the honest question is whether the product's identity depends on an unusual shape or only on the visible outline, which a cover glass can provide.

Where a standard panel is used behind a custom front, the content still has to be composed for the visible area rather than for the full panel.

Square and near-square formats

Square formats suit grid layouts and compact enclosures.

A square active area uses enclosure space efficiently where the content is arranged as a grid of values or as a gauge cluster, which is why it appears in instrumentation and machine controls. Near-square formats - slightly rectangular panels behind a square aperture - are frequently available from standard ranges and are visually indistinguishable behind a bezel, which makes them the cheapest route to a square appearance.

Content design for a square format is simpler than for a wide one, because the layout does not have to manage large horizontal gaps.

Round and circular formats

Round formats are a styling decision with a supply consequence.

A native round panel wastes the corners of the glass sheet it is cut from, which is a real cost, while a rectangular panel behind a circular aperture reduces the visible active area and requires convincing masking. Round displays also demand a round content layout, which changes how much information fits compared with a rectangular screen of the same width. CDTech's notes on custom panel sizes describe the routes and their limits.

Where the product family includes round and rectangular variants, standardising the panel and varying the cover glass is usually the cheaper plan.

Bar and stretched formats

Bar formats come in a defined set of sizes, and anything else is a cutting project.

Bar panels are produced by some makers in resolutions such as 320x120, 480x128, 800x320 and 1024x400, which cover shelf strips, transit information bands and equipment fronts. Outside that set, the route is to cut a standard panel, which introduces edge-sealing and yield risk and therefore a qualification programme. The format comparison is covered in CDTech's bar display selection material and the category overview at bar-type LCD displays.

Bar resolutions are also outside standard video modes, so the host usually needs a controller that generates the native timing.

Matching screen size to viewing distance

Size follows the smallest character the user must read.

The useful starting point is the character height required at the working distance, converted into a physical screen size once the layout is known. Where the display is installed in a panel with a bezel, subtract the masked border from the visible area before deciding. Where the product is a multi information display read from a distance, the values that matter are the character height and the number of values, not the diagonal.

Measuring a cardboard mock-up at the real distance takes minutes and settles the size argument before tooling.

Tooling and order quantity by format

Each step away from a standard panel raises the entry quantity.

Panel format availability is published by manufacturers such as BOE, AUO, Innolux and Sharp Devices Europe, and format and technology trends by research firms such as TrendForce.

Interface consequences of unusual formats

An unusual format usually means an unusual interface configuration.

Bar and stretched resolutions do not map onto standard video modes, so the host must either generate the native timing or a controller must convert a standard mode into it. Round and square formats often use standard interfaces but non-standard resolutions, which has the same effect. The consequence for the programme is an extra board, an extra firmware element and a timing configuration that has to be documented for the product's life.

Where the host is fixed - a standard industrial PC or media player - the controller is unavoidable; where the host is designed for the product, direct drive removes a board and a failure mode.

A decision table by product type

Match the format to the product's function, then to its supply base.

Where the format is genuinely a product requirement, the decision record should state the tooling route, the minimum quantity it implies and the replacement plan.

Specifying size and format in the requirement

Five items prevent the enclosure from being designed around the wrong panel.

• Visible area and outline, with the enclosure aperture and bezel overlap.

• The character height required at the working distance.

• The content layout, including whether it can be recomposed for a different ratio.

• The preferred route: standard panel with custom front, native format, or cut panel.

• The expected annual volume, to establish whether tooling is justifiable.

CDTech manufactures display, touch and bonding in one flow, which makes the standard-panel-with-custom-front route straightforward: the panel stays standard while the cover glass, aperture and print produce the intended appearance. Related material is in the display and touch solutions centre and in the custom LCD display range.

Bar and Stretched Display Selection