Pitch, brightness and content

LED screens · 6 minute read

In the first article we looked at the four questions that decide which type of screen a shop needs. Here we go into three technical decisions that separate a screen that looks good from one that disappoints: pitch, brightness and content.

A word of warning before we start: the figures in this article are indicative. They come from what manufacturers and specialists publish, and they are there to help you ask the right questions. The final decision is made by seeing the screen in place, in its light and at its viewing distance.

Pitch: how much resolution you really need

The pitch is the distance, in millimetres, between one point of light and the next. The smaller the number, the sharper the image looks up close and the more expensive the screen, because it has more points per square metre.

A widely used rule makes a good starting point for assessment: roughly one metre of viewing distance per millimetre of pitch, and double that as a more comfortable distance. Applied to typical shop situations:

Pitch	Can start to be judged from	More comfortable from (approx.)	Typical situation
P1.5–P1.9	1.5–2 m	3–4 m	Indoors, counter, shop window on a narrow street
P2.5	2.5 m	5 m	Shop window with pedestrians on the pavement
P3.9	4 m	8 m	Large shop window seen from across the street
P4.8–P6.6	5–7 m	10–13 m	Façade, projecting sign or a screen mounted high up

That table shifts depending on what is shown. Photos and video tolerate a somewhat larger pitch; small text needs a smaller one. And not everyone sees the same way: for a P2.5, for example, Planar puts comfortable viewing at around 4.3 m.

Watch out for a rule that does the rounds: “the viewing distance is 10 times the pitch”. That calculation gives the result in feet, not metres (Planar). Read in metres, it makes you think you need a much finer, and more expensive, pitch than the site calls for.

There is another consequence that is rarely explained: a shop LED screen has fewer pixels than a television. A 2 × 1 m screen at P2.5 has 800 × 400 points; a Full HD television has 1,920 × 1,080. That is not a defect, because it is viewed from further away, but it shapes the content, as we will see below.

If you are torn between two pitches, the best test is to ask for a sample or to see an installed screen at the same distance your customers will be looking from.

Brightness: how much you need depending on where it goes

Brightness is measured in nits (candelas per square metre). These are examples of what catalogues offer for each location:

Where the screen goes	Catalogue brightness (examples)
Inside the shop	600–1,500 nits
Shop window in the shade	1,500–2,500 nits
Shop window in direct sun	From around 3,500 nits, depending on the model and the orientation
Façade or outdoors	5,000–6,500 nits, with suitable weather protection; check the front and rear IP ratings separately

These are ranges, not exact thresholds. What your shop window needs depends on its orientation, the type of glass, reflections and the hours you want it to be seen.

More brightness is not always better. Inside the shop, an outdoor screen at full output is dazzling, and many run well below their maximum. That is why being able to adjust the brightness matters more than the maximum: with a light sensor or a schedule that dims it at dusk.

Heat deserves a line of its own. A sunny shop window works like a greenhouse, and some screens designed to go behind glass only work up to about 40 °C (the data sheet of one LG model, for example). Ask for the operating temperature range and leave ventilation: excess heat can shorten the life of the power supplies and other electronics.

One more detail, if you expect customers to film the screen on their phones: flicker or lines can appear in the video, and that depends on both the screen and the camera. If people will film it, ask for a test with a phone before choosing the equipment.

Content: what makes the screen work

A good screen with poor content is an expensive piece of decoration. These are the guidelines digital signage specialists repeat most often, as a reference:

• Made to fit the screen. Because it has fewer pixels than a television, content is designed at its real resolution. A video made for TV, played as it is, can lose legibility.
• In its format. If the screen is portrait, so is the content: a landscape video on a portrait screen can lose legibility or show black bars.
• Little text, and large. For screens facing the street, around 8–10 seconds per message and very few words in each are usually recommended (itesmedia). Lettering size is checked on the screen itself and at the real distance: with a coarse pitch you need larger text than you might think.
• Refreshed. Change the content when prices, promotions or campaigns change, and don't leave the same thing up for months: regular customers stop looking at it.

And a practical question: how does content get onto it? The most convenient option for a shop is a player that stores the videos and plays them on its own, on a schedule, without a computer switched on. Content is changed from a phone or the cloud. Before buying, ask who will prepare the content and who will know how to change it.

Before you decide: three checks

1. See the screen in real conditions. A sample or a similar installation, at the distance and in the light of your premises, tells you more than any table.
2. Ask for the full data sheet. Pitch, maximum brightness and whether it can be adjusted, operating temperature range, refresh rate, and whether maintenance is done from the front or from behind.
3. Sort out the content from the start. Who prepares it, at what resolution and how it is changed.

In the next article in the series we will look at what surrounds the screen: permits, the full budget and running costs.

References

• Planar, Understanding viewing distance.
• Barco, What is pixel pitch? (in Spanish)
• LG, LWBC026-GD shop-window LED display data sheet.
• itesmedia, Best practices for exterior-facing digital signage.