Shop window display brightness: how many nits you need

How many nits does a shop window display need?

Plan on 700 to 1,500 nits of front brightness for a screen facing out through storefront glass, roughly three to four times the 250 to 350 nits a standard indoor panel carries, because daylight reflects off the glass on top of the image.

A nit is one candela per square metre, the brightness the panel's face actually emits, and both words on a specification sheet name the same number. The band that decides the purchase is the one your glass sits in during its worst trading hour, not its best. An indoor wall follows the same logic one step down the scale; setting signage brightness for the room's light covers that version, and a window adds reflection on top of everything the room throws at a panel.

Why does a shop window wash out a screen that looks fine indoors?

Daylight on the glass throws reflected light on top of your image, so a screen that looks punchy inside the shop turns grey and washed out the moment it faces a window and the street outside.

Inside, room lighting sits at about 300 to 500 lux and the screen is usually the brightest thing in sight. At the glass, the sky and the opposite frontage are brighter than any panel, and the viewer sees their reflection sitting over your content like grey smoke. The cure is contrast: the panel needs enough nits that its own light swamps the veil. How much swamping is enough is arithmetic, and the worked example below runs it. The same decision indoors is the 250 or 500 nit choice for an in-store touch kiosk; a window pushes the answer three to four times higher.

Which brightness band fits your window?

Match the band to the worst light your window sees, not the best: 700 to 1,500 nits covers a daylight window without direct sun, 1,500 to 2,500 nits covers a shopfront that catches sun for part of the day.

These bands are the signage trade's working rule of thumb, and the deciding input is the brightest hour of your trading day. Stand outside the window once at its worst light, mid-morning or mid-afternoon depending on the frontage, and write down what the glass sees: open sky, opposite buildings, or direct sun.

Does the window glass itself change the number?

Yes: uncoated glass reflects about 4 percent of the light striking each surface, and the sun trapped behind the window heats the air around the panel, so both the reflection glare and the panel's rated operating temperature belong in the decision.

Two uncoated surfaces add up to roughly 8 percent, and glass with an anti-reflective coating cuts that hard, so if the landlord offers treated panes, take them. Heat matters as much as glare: sun through glass turns the recess behind the window into the hottest air in the shop, so leave an open gap behind the panel for warm air to escape and check the rated operating temperature before boxing anything in. The panel-mount series we sell is rated -10 to 60 °C operating in 95 percent non-condensing humidity, and it offers an auto brightness sensor combined with a sunlight-readable panel among its brightness options; other models print their rating on the page or the quote. The sensor earns its keep twice in a window: full output through the trading day, then a drop after dusk so the shopfront stops glowing over the street at night.

How big should the text be for someone on the pavement?

Size street-facing text at 20 ft of viewing distance per inch of capital letter height, the fast-reading end of the FHWA planning figure, so a passer-by standing 16 ft from the glass needs capitals about 0.8 in, or 20 mm, tall.

The FHWA planning figure is 30 ft of viewing distance per inch of capital height, and 20 ft per inch when people read at walking pace without stopping, which is exactly what a street window gets. The metric shortcut: 4 mm of capital height per metre of viewing distance at the fast rate, 3 mm per metre at the slow one. Line spacing follows the same system at 1.7 times capital height, so 21 mm capitals sit on 36 mm between line centres. Video carries no text rule; the height rule applies to menus, offers and opening hours, which are the words a passer-by actually reads. Once you know the distance, the guide to screen size and viewing distance carries the full method for picking the panel diagonal.

What does a worked example look like for a real shop window?

A shaded window with a reader 5 m out points to a 1,000 to 1,500 nit panel with 21 mm capitals, and the same shopfront with low sun on the glass needs 2,500 nits, a shade, or both.

Scenario: a bakery on a north-east frontage. The screen hangs 0.5 m behind the glass, the nearest reader stands 5 m away on the pavement, and daylight reaches the glass but direct sun never does.

Text: 5 m is 16.4 ft. At 20 ft per inch, capitals need 16.4 ÷ 20 = 0.82 in, about 21 mm, on 36 mm line spacing.

Brightness, shaded case: assume 5,000 lux of daylight on the glass, a fair figure for a shaded vertical window under a bright sky. Two uncoated glass surfaces reflect about 8 percent, so the veil over the image is 0.08 × 5,000 ÷ 3.14 = 127 nits. Contrast is panel brightness plus veil, over veil. A 300 nit indoor panel: (300 + 127) ÷ 127 = 3.4:1, right on the 3:1 floor that accessibility guidance sets as the minimum for large text, with nothing in reserve for a brighter sky. A 1,000 nit panel: (1,000 + 127) ÷ 127 = 8.9:1, comfortable through the trading day. Decision: buy in the 1,000 to 1,500 nit band.

Sun case: a south-west corner of the same street catches low sun on the glass from mid-afternoon. Assume 30,000 lux striking the glass, mid-range for direct sun, which delivers up to about 100,000 lux on a surface it hits square on. The veil climbs to 0.08 × 30,000 ÷ 3.14 = 764 nits. A 1,500 nit panel: (1,500 + 764) ÷ 764 = 3.0:1, on the floor with the sky still climbing. A 2,500 nit panel: (2,500 + 764) ÷ 764 = 4.3:1, which passes, in the hottest air in the shop. Decision: 2,500 nits, and take the shade anyway; a blind cuts the veil and the heat together, and a shaded 1,000 nit panel beats an exposed 2,500 nit one on both.

Recommendation: Buy 1,000 to 1,500 nits when the window sees daylight but no direct sun, step to 2,500 nits only when sun strikes the glass during trading hours, prefer a blind or a deeper recess when the sun sits on the window for hours, and set the off period from midnight to 6 am on whichever scheduler your setup has.

How do you switch the screen off from midnight to 6 am?

Set the off period from midnight to 6 am as a daily on and off time in the player's schedule, and use the screen's own timer menu or a mains timer on the adapter where the player cannot schedule.

Three tools do it, and any one is enough:

1. The player's schedule. Set 00:00 off and 06:00 on as a daily repeat; scheduling a retail digital signage display on and off daily walks through the steps.
2. The panel's own timer. Commercial panels usually carry an on and off timer in their settings menu, driven by the panel's clock, so the screen wakes and sleeps on its own.
3. A mains timer. A 7-day digital timer between the socket and the power adapter switches the wall outlet itself. Our panel-mount screens draw 18 W showing still images, so any timer rated for household loads carries one; a high-brightness window panel draws more, so match the timer to the adapter's rating.

Set the on time 10 minutes before the doors open so the player has finished starting when the first customer walks past. The overnight break also saves backlight hours and keeps the shopfront dark after closing, which some city rules on illuminated displays ask for; one question to the local planning office settles it.

When is a shop window screen the wrong choice?

Pick something else when the window sits in permanent shade, where a 400 to 500 nit indoor panel is enough, or when the sun pounds the glass through the whole trading day, where even 2,500 nits struggles and a blind or a printed graphic wins.

A north-facing frontage in the northern hemisphere misses the sun for most of the day, so an indoor panel does the job there and the money you save buys content or a bigger diagonal. An all-day sun trap is the opposite case: even 2,500 nits fights a losing battle against glass that never gets relief, and a blind, an awning or a deeper recess beats another hundred nits. The third case is distance: if the message is video watched from across a wide street, a bigger ordinary panel set 1 m back in the shade of the recess beats a small ultra-bright one flat against the glass, because distance sets the size and the glass sets the brightness. And if you are still weighing a looping player against a touch kiosk for the shop itself, interactive versus simple digital signage for a small shop settles that before brightness does.

What should you ask for before you buy?

Ask each supplier for the front brightness in nits, the rated operating temperature, whether an auto brightness sensor is offered, whether the player schedules daily on and off times, and how you load new content on site.

Work down this list, and keep the answers on the quote:

• Front brightness in nits at the panel face, and which band it lands in.
• Rated operating temperature, and how the housing vents behind glass.
• An auto brightness sensor, offered as an option.
• Daily on and off times on the player or the panel, set for your trading hours.
• How content is loaded and changed on site; a card or stick you swap yourself keeps updates on-site and subscription-free on offline players.
• Portrait or landscape, outside dimensions, and the cut-out size if a millworker is building the recess.
• Lead time, warranty and returns terms for that specific model.

For the larger wall models we quote per project, the quote confirms software, ports, power, orientation, rating, lead time and warranty for that model. Our panel-mount series prints its figures on each display page and is ordered through the checkout.

Bring the supplier four things so the quote lands on the right panel the first time: two photos of the window at its brightest trading hour, the compass direction the frontage faces, the distance from glass to the farthest reader, and the off hours you want enforced.

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