LCD panel brightness is normally expressed in terms of Nits or Candelas/meter2 (cd/m2), they are equivalent, and refers to the manufacturers measurement under the following conditions:
- After the backlight has had time to warm up to reach full potential,
- From directly in front of the middle of the panel,
- With transmissivity at maximum, so if the panel is normally white then probably with no input signal or if the panel is normally black then with a full white signal.
There are no standards for suitable brightness levels for various applications which is reasonable considering other factors will affect the outcome but as a general guideline it would seem that the following ranges apply:
- Notebook type computers: Around 200~250 Nits
- Desktop monitors: Typically up to 450 Nits
- TV’s and video displays: 400~600 Nits
- Public displays: Generally around 600~700 Nits
- Outdoor displays: 700~1,500 Nits.
- Sunlight readable: >1,000 Nits
Contrast: As I was being told this morning a 700 Nit panel with excellent contrast proved to be considerably better in an outdoor application than a 1,500 Nit panel with lower contrast.
Surface finish: A gloss finish to the display cover glass with maximize the apparent brightness of the display but will also reflect more. On the other hand a haze or matte finish will soften the image but have less reflection.
Cover glass: A touch panel or protective cover glass will block some of the light and could easily reduce the brightness by 5 to 15%.
The bottom line is that it is very difficult to make a decision based on the specifications and the display needs to be evaluated in its environment.
Low Light Conditions
Most displays are designed with brightness targeted at normal daytime lighting levels however some applications require low light visibility. Examples include monitors on boats, public digital signage, displays in security and military applications.
Ambient Light & Auto Adjustment
Digital View provides a number of solutions for making monitors and display systems with auto-adjusting backlights, see our blog on Ambient Light Sensor.