What is the logic behind "Brother Backlit Sky" in the book Understanding Exposure?

Question

I don't know if this question is too specific, but after reading Understanding Exposure, I can't understand very well the reasons and logic behind Brother Backlit Sky and their brothers. Although I did see that the pictures result more naturally pleasing.

I don't know if I can explain here what the book says as it's inside a paid book, but it has something to do with the metering system trying to convert everything to 18% gray.

Update

From the book, you use Brother Backlit Sky when shooting backlit sunrise or sunset landscapes. Take a meter reading to the side of the sun and use it to make your image.

Answer 1

All the 'Brothers' in Understanding Exposure are an attempt to give you a simple, normally consistent thing that you can meter off that shouldn't be too far to the extreme. Metering off the sky, plant foliage, and other reflectively moderate items give you a solid baseline.

The idea is that here is an object that relative to the normal scene should be a bit..in the middle so to speak. He's not asking you to meter off something pure black or pure white because then it would throw the scene out of whack.

In reality, its a bit of a novelty to learn until you really 'understand exposure' in which case you should be picking your metering based on your own judgement of whats important to you in the scene.