1.8 Section 1: The Core Exposure Triangle

Aperture Priority

Hold aperture; the solver picks the matching shutter.

Where to find it

Viewfinder Priority Mode chip Aperture

Summary

Pick your aperture, let the meter pick the shutter. The classic depth-of-field-first workflow: you choose how much background blur or sharpness you want and the app finds the shutter speed that matches the scene EV.

Tap to zoom — actual screenshot from the app

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How it works

What it does

Switch the priority chip to Aperture. Pick the f-stop you want (e.g., f/2 for a portrait, f/11 for a landscape). The meter holds that aperture and varies the shutter to match the scene's metered EV. Move to a brighter or darker scene and the shutter changes; the aperture stays put.

When to use it

Anytime depth of field is the variable that matters most: portraits where you want a specific bokeh look, landscapes where you want everything from foreground rocks to mountains in focus, macro work where you need a specific working aperture for diffraction balance.

What the solver does

The solver computes the shutter as scene_EV - log2(aperture_squared) + log2(ISO/100) and rounds to the closest standard or custom shutter increment. If the answer falls outside your camera's shutter range, it warns and suggests a different aperture or ISO.

Pairs with stop increment

Recommended shutters land on the stop increment you have selected (FULL/HALF/THIRD). If you click only in halves, the solver returns a half-stop value rather than a third that you cannot actually set.

Implementation notes (for developers)
ExposurePriority.APERTURE. Solver holds aperture and varies shutter to match scene EV.

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