Your camera meter assumes the world averages out to a middle gray, roughly the brightness of a concrete sidewalk. It reads the scene, compares it to that target, and tells you how far off you are. The reading is a starting point, not a verdict.
Point that same meter at snow and it will underexpose, because it wants to drag the white down to gray. Point it at coal and it will overexpose. The meter is consistent and often wrong.
Metering modes change which part of the frame the camera weighs. Matrix or evaluative mode reads the whole scene and applies its own logic. Center-weighted favors the middle. Spot reads a tiny circle exactly where you aim it.
Most of the time matrix gets you close. When a subject is backlit or the frame has extreme contrast, spot metering on the face gives you a reading you can actually trust.
The meter does not know what matters in your frame. You do. Aim it at the thing you refuse to lose, then bias the result.
Inside the viewfinder you will find a row of tick marks with a zero in the middle. Each mark is a third of a stop. The moving bar shows how far the camera thinks you are from its target.
Zero is not holy. If you aim at a bright sky and want to keep the skin tone open, dropping one or two thirds into the minus side is a choice, not a mistake.
When you shoot in an automatic mode, exposure compensation lets you nudge the advice of the meter without leaving the mode. Turn it down when the scene is darker than the meter thinks. Turn it up when the scene is bright enough to fool it.
Find the compensation dial and learn it by feel. It is the fastest way to bend an auto mode to your will.
Take three shots of a white wall: one at the meter reading, one a stop over, one a stop under. Look at them on a big screen. You will never forget which one the meter wanted and which one you wanted.
The exposure triangle controls how bright your shot looks. Read aperture, shutter speed, and ISO so your exposure choices become deliberate, not accidental.
A properly exposed face carries a scene. Learn to expose for skin, protect highlights, and keep faces readable even when the light fights back.
Both misses cost you, but not equally. Compare overexposure and underexposure so you know which mistake to avoid and which one you can repair.
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