# SoftBank Robotics documentation What's new in NAOqi 2.8?

# ALDarknessDetection

NAOqi Vision - Overview | API

## What it does

ALDarknessDetection enables to check whether or not the robot is in a dark environment.

A darkness value is computed for each frame returned by the camera. This value is stored in the ALMemory. When the robot detects for the first time that that the environment around it is dark (i.e the darkness value is greater than a threshold) an event is raised.

## How it works

This function first computes a value between 0 and 100 corresponding to the lighting conditions of the environment around the robot:

- 0: bright environment
- 100: dark environment

This value is then compared to a darkness threshold:

- if it is smaller than the threshold, the surrounding environment is not considered as dark.
- if it is greater than the threshold, the surrounding environment is considered as dark.

The darkness threshold value can be accessed with the function `ALDarknessDetectionProxy::getDarknessThreshold`. It has a default value of 60 but it can be changed with the function `ALDarknessDetectionProxy::setDarknessThreshold`.

## Performances and Limitations

The camera AutoExposition parameter (and the AutoGain parameter, if it exists) of the camera must be activated for this module to work properly.

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