There are really two elements to mastering exposure in your photography, the theory of exposure, and the real world application. Here's a great video by bird photographer virtuoso Arthur Morris, a Canon "Explorers of Light" program instructor. His expertise and tips on mastering exposure help you understand when to bend the rules and when to break them if what you already know isn't producing the results you know you can achieve.
Getting the Right Exposure
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Further Understanding of the Histogram
Some images produce a spike in the histogram grouped towards the center, others show more evenly spread from left to right. This is a visual representation of the dynamic range in the image - the total spectrum of dark to light in the image. High end cameras often have sensors capable of capturing a large dynamic range, this enables a larger broader spectrum of luminance to be captured without clipping on either end. If you cannot achieve a setting without having either end clip, this just means the dynamic range of the image is too broad for your camera's sensor to capture. Mastering exposure entails not only knowing how to solve the problem, but understanding the capabilities of your gear.
More videos on Bird Photography by Arthur Morris:
Canon: Bird Photography with Arthur Morris: Arthur's Gear Bag
Canon: Bird Photography with Arthur Morris: Tele-Extenders
Canon: Bird Photography with Arthur Morris: One Shot and AI Servo AF
Canon: Bird Photography with Arthur Morris: Sunrise and Sunset Blurs and Silhouettes