NITS and Digital Signage
With digital signage being present in most public places – from entertainment venues to educational institutions or businesses – it is viewed every day by over 70% of the population. It is used to engage with audiences (old and new) in captivating new ways. Despite digital signage ROI’s being more than proven, it is still a complex field (due to the many components involved). Today we’ll clarify the importance of choosing the right display.
Digital signage enables messages to be conveyed in different ways. As attractive and well-made as that message may be, it will only make an impact if its target audience is able to see it.
The display is the component responsible for presenting the message, and it needs to be prepared for as many environmental conditions as possible in order to maximise its life expectancy and usability. For instance, a display or kiosk meant for indoor use has different requirements than one meant for outdoor use (which, besides having a constant change in lighting and reflection conditions, will also need to be up to other atmospheric conditions, improper usage/vandalism, etc.). This will influence the kind of components chosen to ensure the best results, particularly the kind of display that will be used.
Light output and brightness
What is usually called brightness is in fact luminance.
The difference between these two terms derives from luminance being the actual photometric measure of luminous intensity per unit area of light travelling in a given direction (‘Candela per Square Meter’ [cd/m2]), and serves as an indicator of how bright the surface will appear. Brightness, however, is the perception prompted by the luminance of a visual source that seems to be radiating or reflecting light, but it isn’t necessarily proportional to luminance.
In short, luminance is in fact an objectively measurable feature, which means it can be quantified, whereas brightness is the subjective interpretation of perceived luminance, and can only be referred to with regards to a scale (e.g. in percentage or a relative scale – such as brighter than, less bright than).
How did Nits come into play?
It began with the widespread availability of HDR (High Dynamic Range) TVs, and it is the way in which light output is quantified (with the purpose of serving HDR, the more Nits a TV has, the higher is the light output). One Nit equals one candela per square meter (cd/m2), a standardized measurement of luminous intensity, where the candela indicates how much light energy coming from a source is likely to be perceived by people and Nits indicate how this energy is distributed over an area (which is the reason behind a 400 Nit smartphone screen seeming as bright as a 400 Nit laptop screen, even though the laptop screen is emitting more light in total). To put it in numbers, any average tv may range between 100 and 200 Nits but if they are HDR-compatible, they may be able to output from 400 to 2000 Nits.
However, it begs disclaiming that even if a display claims to be able to output 1000 Nits it doesn’t necessarily mean that it will constantly have that output. Since most frames / scenes often exhibit a range of bright and dark content, coupled with variations in colour, different levels of light output will be required.
Why choose a display with more or less Nits?
As was mentioned, in order for the message to be readable, the display needs to be able to be seen. The most relevant attribute is the external lighting conditions (the sun, for instance, or the type of lightbulb – such as fluorescent, halogen or led) which will impact heavily on the readability of the screen. Naturally, an outdoor display will require a screen with much higher Nits than an indoor display, to adapt to the challenges posed by the sun.
However, just being bright does not automatically infer that it can be seen well. It takes the optimum combination of brightness, contrast ratio and the anti-reflection treatment used to provide the best image.
In sum, while Nits prove to be essential for a screen readability, there are some other factors at play that will also impact the readability of the message displayed.