Why does my camera show a different exposure reading at the same settings in different light?

Your camera's exposure meter reads the actual light in the scene in front of it, not your chosen settings — f/8, 1/125s, ISO 400 is a fixed exposure value regardless of what you point the camera at, but the meter's job is comparing that fixed exposure against how much light a specific scene actually has, and that changes constantly as you move, as clouds pass, or as your subject changes.

Fixed Settings, Variable Scene Brightness

In full manual mode with no auto-ISO, your actual exposure genuinely never changes between shots at the same three settings — what changes is the meter's assessment of whether that fixed exposure is correct, too bright, or too dark for the specific scene you're now pointing at. A meter reading of '+1 stop' in bright sun and '-2 stops' in shade at the identical f/8, 1/125, ISO 400 doesn't mean your camera behaved inconsistently; it means those two scenes genuinely have different amounts of light, and the same fixed exposure sits differently relative to each one.

Why Metering Mode Adds a Second Layer of Variation

Beyond raw scene brightness, your meter reading also depends on which metering mode is active — spot metering reads a tiny portion of the frame, evaluative/matrix metering weighs the whole scene with some bias toward the focus point, and center-weighted sits between the two. Pointing the same camera at the same scene with a different metering mode selected, or even just recomposing so a bright sky enters or leaves the metered area, can shift the reading meaningfully without the actual light or your settings changing at all.

Understand what changing any one exposure variable actually does to the other two in the Exposure Triangle Solver.