Is it dark?
This Ambient Light Sensor can help you with that question.
- 2.16 or 2.33 GHz (Model A1211) 15" MacBook Pros
- 2.2, 2.4, or 2.6 GHz (Model A1226) 15" MacBook Pros
Lifetime Warranty - This iFixit product is guaranteed to function as long as you have it.