Retail touch screen kiosk brightness: 250 or 500 nits in store

The answer: 500 nits on the floor, 250 in a dim corner

Panel brightness is rated in nits, which are candelas per square metre. The commercial indoor range runs from 350 to 500 nits, the span signage buying guides treat as sufficient for interiors without direct sunlight. A screen that should pull people in from the aisle wants the top of that range: 500 nits. The 250-nit panels in big tablet-style units sit under the commercial range, and they survive in exactly one kind of spot: a dim corner with no windows, where the ceiling lights sit behind the customer and nothing bright reflects off the glass.

Read the table as a purchase rule, not a physics lesson. The third and fourth rows are where in-store screens usually sit, because most shops have glass somewhere, and glass is what kills a 250-nit picture.

What store light does to a picture

Two kinds of light hit the glass, and they fail a screen in different ways. Diffuse light from the ceiling lifts the black level of the whole picture evenly; a general retail floor is lit to around 300 to 500 lux, the level lighting guides give for shop space. Specular light is the one that kills in-store screens: a sun patch or a bright window reflected in the front glass sits on top of the image and crushes the contrast right where it lands.

Plain untreated glass reflects about 5% of the light that hits it, and bright daylight through shop glass puts 5,000 lux and more on a screen face. Those two numbers, 5% and 5,000 lux, decide whether 250 nits is enough, and the example below runs them. Tuning a screen's brightness level against the light already in the room is a separate job, covered in setting signage brightness for the room light; this page is about picking the rating before you buy.

Worked example: 250 nits and 500 nits under the same light

Take a 32 inch touch screen on an aisle end, 16:9, playing video ads, with a plain glass front reflecting 5% of incident light. Reflected luminance is L = E × ρ / π, where E is the illuminance on the glass in lux and ρ is the reflectance; dividing by π, about 3.14, converts reflected lux to candelas per square metre. Take the panel's black level as near zero, so contrast is (panel brightness + reflection) / reflection.

Average lit aisle, E = 500 lux: L = 500 × 0.05 / 3.14 = 25 / 3.14 ≈ 8 nits. The 250-nit panel gives (250 + 8) / 8 ≈ 32:1 contrast, and the 500-nit panel gives (500 + 8) / 8 ≈ 63:1. Both are watchable, which is why some 250-nit screens in dim shops look fine.

Sun patch on the glass, E = 5,000 lux: L = 5,000 × 0.05 / 3.14 = 250 / 3.14 ≈ 80 nits. The 250-nit panel falls to (250 + 80) / 80 ≈ 4:1, and video at 4:1 local contrast reads as washed out. The 500-nit panel holds (500 + 80) / 80 ≈ 7:1, still watchable. A 1,000-nit panel gives (1,000 + 80) / 80 ≈ 14:1, which is the case the high-brightness class is built for.

The decision falls straight out of the two cases. Diffuse store light leaves a 250-nit panel standing; the sun patch kills it. You cannot schedule where the sun stands, so a screen that has to be noticed gets 500 nits as the floor, and any position sun crosses gets 1,000-nit glass, a shade, or a different wall.

Size and viewing distance in the 24 to 32 inch band

The 24 to 32 inch band is generous for a touch kiosk, because the customer closes to arm's length. The road-sign planning figure is 30 ft of viewing distance per inch of capital letter height, with 20 ft per inch the safer figure for fast reading. At 1 m, which is 3.3 ft, the 30 ft figure asks for capitals of 3.3 / 30 = 0.11 in, about 8 pt, and the 20 ft figure asks for 3.3 / 20 = 0.17 in, about 12 pt.

Every panel in the band clears that, so size is decided by reach and the enclosure instead. A 24 inch panel suits one-handed browsing at a counter; 32 inches suits a screen two people read together. Most panels in the band run 1920 x 1080, which is plenty at that distance. Ask for capacitive touch, which answers a light swipe the way a phone does; the touch panel technology comparison sets out the types. The fuller method for matching screen size to viewing distance is in the guide to screen size and viewing distance.

The touch-to-website loop and the lockdown

The touch-to-website loop has four parts, and the software you buy has to state all four in its documentation.

1. The video playlist runs while nobody is touching the screen.
2. A touch pauses the ads and opens your website in a locked browser window, with navigation kept inside your own domain.
3. An idle timer returns the screen to the ads. Set it to 15 to 30 seconds, short enough that the next customer finds the ads already running.
4. After a power cut, the player is designed to come back into the locked loop with nobody logging in.

Two things to know about the lock. On Android, the lock is enforced by the kiosk app, and how sealed it is depends on the app; some setups leave a determined user a route out through the home gesture. An operating system whose kiosk mode is part of the platform itself seals harder. Locking a Windows-based kiosk down to one application is a documented configuration job, and a worked example of kiosk lockdown and auto-start on a Windows runtime shows what that configuration covers. If you are still weighing touch against a plain ad loop, interactive or simple digital signage for a small shop sets out that choice.

We sell the screen, not that loop. Our panel-mount units are built to play images and video from a microSD card or USB stick, with no subscription; the touch-to-website layer is separate software, and what a unit we quote you actually runs is written into the quote.

When to pick something else

No touch: if the screen only plays ads and nobody is meant to poke it, drop touch and buy a plain signage panel in the 350 to 500 nit range. Touch glass is a cost you pay only when the website interaction earns it.

Window wall or sun: the example shows what direct light does to anything under 500 nits, so a sun-crossed position gets a 1,000-nit class panel, a shaded recess, or a different wall.

Tablet-style hardware: the Android tablet-style units are the cheapest way to trial the idea, and fine for one screen. Before you order a row of them, check the build; the piece on repurposing an Android ad display as a shop kiosk lists what to check before a tablet-style unit becomes a permanent fixture.

What to ask for before you order

Six answers decide the order:

• Rated brightness of the panel in nits, at full setting, from the spec sheet, not a typical figure.
• Touch type: capacitive, and whether multi-touch gestures work on your website.
• The idle timeout setting, and whether the screen returns to the ads automatically.
• Whether the software's own documentation states the player is designed to relaunch into the locked loop after a power cut.
• Mounting: the VESA pattern, the enclosure depth, and where the power and any cabling land.
• What the unit runs. Our larger wall models through 75 inches are quoted for the project, and the quote confirms the software, ports, power, orientation and touch options for that exact unit; the sizes are on the displays range page.

Recommendation: Buy a 500-nit panel with capacitive touch for any touch kiosk standing on the sales floor, sized 24 to 32 inches for arm's-length use, with the idle timeout at 15 to 30 seconds. Keep a 250-nit tablet-style unit for a dim, windowless corner, and only after you have held one there through the brightest hour of the day. Put a 1,000-nit class panel, a shade or a different wall anywhere sun crosses the glass.

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