Display visibility and brightness in outdoor lighting
19 Feb 2020
A more graphic blog article with similar content is at the following web page.
Original article from 2 Dec 2010, updated content on 19 Feb 2020:
Each generation of our rugged handheld computer models are designed to provide the best available display technology for outdoor visibility and function. Available display technologies have improved over time, as is visible on the latest generation of our products.
Although using a NIT rating or lumens measurement are common methods to rate the brightness or luminance of displays, it is not a good measure of how viewable the display is in an outdoor setting. Display technology (reflective, transmissive, transflective) and bonding process (LOCA, drybond, no-bond) are bigger factors in how viewable it is in natural lighting. A display that has a high measurable brightness can still provide a poor outdoor viewing experience due to the display technology and bonding process. Similarly, you can have a display technology such as e-ink with no measurable brightness and yet be highly visible outdoors. These are just a few factors that contribute to the outdoor viewing experience.
If a NIT rating is still needed such as to apply for a specific government contract, the TFT-LCD display on the Mesa 3 and Mesa 2 is 450 nits (about 42 lumens) or 450 cd/m^2 or Lux (lumen per square meter), both for the later US Micro MIPI display or for the previous Sharp LVDS display.
Some specific conditions can potentially cause the display to be less visible than normal. Such conditions can include (but may not be limited to) the following.
- Display backlight and/or contrast is dim (particularly with transmissive instead of transflective displays). You may be able to manually adjust this setting to improve visibility.
- Tactical Mode may be enabled and needs to be disabled.
- Screen protector sheet is installed over the display. Crystal clear (glossy finish) protectors may cause undesired reflections or glare, while anti-glare (matte finish) protectors may allow less light to and from the display. Removing or swapping the screen protector may help.
- Wearing polarized sunglasses (particularly when the polarization of the glasses aligns with the polarization of the display). Switching to different or non-polarized sun glasses may help. The display of the Mesa 3 and later Mesa 2 units work well with polarized sunglasses, or a polarized screen protector sheet may also be available, such as we provide for previous Mesa 2 units.
- The display controller is not behaving properly, requiring a Hard Reset (hold the Power button for a full count of 20 seconds) or extended power removal (pull battery pack(s) and wall charger for at least 20 minutes).
- The display is damaged (such as extensive scratches), partially disconnected, or has a defect requiring repair or replacement.