Nits. What are they and why they don’t tell the whole story about display brightness and visibility. In this article, we will cover some of the display factors that go into having a device that performs at a superior level in outdoor environments.
Nits are the most common and most often used technical specification when promoting a device’s screen brightness level. A nit is a unit measuring the luminescence, or brightness, of a display. Otherwise known as the candela per square meter. To put this into perspective, one nit gives off the light intensity of a common wax candle. Naturally, it’s assumed that the higher the nit rating the better. However, the brightest display isn’t always best. Nits are only one part of the equation and are used to describe the brightness of the screen for devices ranging from smartphones, laptops, and large big-screen TVs that are never meant to be viewed anywhere but in a living room or indoor area. This is one reason it can be a misleading specification.
Battling screen glare
It’s important to know what battle is being fought when discussing the visibility of a display being used outside. Screen glare from the sun is probably the biggest factor in having a sunlight-readable display. The sun can easily washout or overpower the image on a screen, even on a device with a 600-nit display. So, what’s done to reduce glare? Many consumer devices try to simply make the display brighter to combat the effects of the sun. This leads to faster battery drain and potentially a hotter device that can shut down or slow down while in the field. Here at Juniper Systems, it was decided that the trade-offs of just sticking an ultra-bright set of LEDs in our devices to combat sunlight wasn’t the right approach. There are many factors to consider when choosing a device for use outdoors. Here are some things to consider.
Optically bonded (laminated) display
A large piece of glass, like on a tablet, can easily act as a mirror and can be highly reflective and enhance glare while outside. Some steps can be taken in the development of a device to minimize how reflective a glass display will be when being used. At Juniper Systems we have taken appropriate steps to reduce glare across our entire range of rugged devices. We know that our devices are used outside in all weather conditions.
One solution to reducing screen glare on a glass screen is to make the space between the layers of the display smaller or to fill that space and bond them together. Displays on Juniper Systems’ devices are optically bonded, meaning the layers of the display are bonded to one another. In the case of the Mesa Rugged Tablet, the cover glass, touchscreen, and LCD (Liquid Crystal Display) are optically bonded with a clear adhesive. This is often referred to as a laminated screen and removes the air gap between layers. Optical bonding allows for less light to reflect off the different layers of the cover glass, touchscreen, and display assembly. This reduces the reflection of incoming light and increases the brightness and image clarity. Optical bonding can increase a display’s brightness by about 15% over a non-optically bonded display.
Touchscreen technologies
Another step to reduce glare and increase visibility is to consider the touchscreen technology used in a device. Using a capacitive touchscreen over a resistive touchscreen not only gives the screen fewer layers of materials for light to pass through, but it also gives the device a more durable screen.
Resistive touchscreens have an air gap as part of their design inherently adding a reflective surface and reducing viewability. Touchscreen materials are also important. Generally, touch screens are made of glass or polymer sheets. Resistive touchscreens have a polymer (plastic) touch surface. Polymer touchscreens are very susceptible to scratches and can be susceptible to UV light which over time will cause yellowing or clouding of the material reducing visibility.
Capacitive touchscreens allow for a glass touch surface. Glass maintains its clarity over time even in UV exposure. A tempered glass screen is much more durable and adds to the ruggedness of the device. It is also easy to add a screen protector to glass displays that help with reducing glare. This combination gives a device better durability and screen clarity.
Display technologies: Transmissive vs. Transflective
1. Transmissive
Transmissive LCD means the LED backlight of the display must be turned on to ensure readability for the user.
While this does help the screen be readable, it requires more power (battery) to get a bright and crisp viewing experience in a high ambient light situation, like being outdoors. This produces more heat. These are important factors for battery life and ultimately will reduce the performance and longevity of a device and its hardware.
2. Transflective
Transflective LCD on the other hand acts as a reflective display to the sun or ambient light. This in effect amplifies the total effective nits and produces a highly-visible display. The transflective LCD does not require more power or produce as much extra heat to achieve greater readability.
Overall, the transflective display has better viewability in comparison to transmissive and reflective only displays. Using a transflective display along with optically bonded layers allows for a device with a lower nits rating, on paper, to produce just as bright and clear of an image in outdoor conditions.
System performance trade-offs
One final piece to finding the right balance in display readability is to consider some system performance trade-offs. Often, a bright screen comes with using several LED backlights that use more power, essentially consuming battery power faster, and generating heat. When heat is generated in a computer with the form factor of a tablet, the heat often has nowhere to escape to. This makes for a hot touchscreen surface and it adds strain on the device and often leads to the tablet’s processor running at a slower speed to reduce heat production.
Having more granular control over settings and display brightness allows users to set their devices to the current conditions. For example, a user using a Mesa 3 in the bright sun can confidently increase screen brightness to maximum and not worry about a device that will heat up to the point of either shutting down or running at a slower speed to reduce heat. The combination of optically bonded screen layers, transflective display, a capacitive touchscreen, and granular control of device settings allows for a sunlight-readable display.
Test it first hand
Having a usable device in any condition is something that Juniper Systems strives for with all of our devices. If you find yourself in the market for a rugged device to do your fieldwork then reach out to us. We can help you with a demo a unit. This demo period serves as an opportunity to test our devices in the environment that you work in each day. With years of feedback from customers, Juniper Systems is confident that our devices will fit your computing needs. Reach out to us below.