The specification for the brightness of the 270c display is between 14.5 and 20.5 Foot Lamberts
1) Make the measurements from a blank SimpleText document. This will provide you with a white background.
2) Turn the brightness up to the maximum.
3) Allow the display to warm up for approximately 10 minutes before taking a measurement.
The readings that I measured were:
Sekonic; Model 246 Measured between 10 to 12 on the red scale.
Sekonic; Model 248 Measured approximately 10.
Theses readings are within the specification. The light meters use a different scale then Foot Lamberts so the readings of 10 to 12 are within spec.
These Sekonic light meters are available in the Service Price Pages. Order part # 076-0310. The Sekonic Model 246 is the current model that Apple ships.