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Calcolatore del Triangolo dell'Esposizione (ISO, Scatto, Apertura)

Calcola esposizioni equivalenti tra apertura, tempo di scatto e ISO. Ogni clic corrisponde esattamente a uno stop, con supporto per frazioni di stop e output in tabella EV.

ISO

Apertura

Otturatore

Valore di esposizione (EV a ISO 100)

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Δ dalla base: 0 stop · Ultimo bloccato: nessuno

Se cambi…	Per mantenere l'esposizione, regola…

Come funziona il calcolo

Ogni "stop" corrisponde a un raddoppio o dimezzamento della luce. Raddoppiare l'ISO, aprire l'apertura di uno stop o raddoppiare il tempo di scatto aggiungono tutti uno stop. Le esposizioni equivalenti mantengono costante la somma ISO_stop + apertura_stop + otturatore_stop.

EV a ISO 100 = log₂(N² / t), dove N = apertura e t = tempo di scatto in secondi. Regoliamo a step di 1/3 di stop per adattarci agli incrementi della ghiera della fotocamera.

Come funziona il calcolo

The headline figure is exposure value at ISO 100: EV = log₂(N² ÷ t), where N is the f-number and t is shutter time in seconds. The default f/8 at 1/125 s gives EV 12.96. Underneath, the Δ from base readout counts stops of brightness relative to the ISO 100 · f/8 · 1/125 reference by summing log₂(ISO ÷ 100), log₂(64 ÷ N²) and log₂(t × 125) into a single signed number.

The three dropdowns are ladders of genuine camera values: ISO 50 through 102400 and apertures f/0.95 through f/32 in third-stop increments, shutter speeds 30 s down to 1/8000 in whole stops. Changing one axis moves another to hold the exposure matched, and the Lock ISO, Lock Aperture and Lock Shutter buttons take that axis out of contention — click again to release. Reset (ISO 100 · f/8 · 1/125) returns everything to the reference.

Check the compensating value against your camera before you shoot. The tool snaps to the nearest ladder entry, and because shutter is a whole-stop list while ISO and aperture are thirds, a third-stop change can round away to nothing on the shutter axis. It is also pure light arithmetic: no reciprocity failure, no ND filters, no T-stop transmission losses, and no accounting for the depth of field and diffraction that separate f/1.4 from f/16.

Domande frequenti

What does EV 12.96 at ISO 100 actually mean?

It is log₂(N² ÷ t) for the default f/8 at 1/125 second — a measure of how much scene light that combination is set for, roughly bright overcast daylight. Higher EV means a brighter scene, and each whole number is one full stop.

If I open the aperture two stops, how much faster must the shutter be?

Four times faster. Each stop doubles the light, so two stops is a factor of four: f/8 at 1/125 becomes f/4 at 1/500. ISO could absorb the same change instead, dropping from 400 down to 100 for an identical result.

Why are shutter speeds whole stops when ISO and aperture use thirds?

The shutter list follows the classic camera dial, 30 s down to 1/8000 with each entry double the last. ISO and aperture use third-stop ladders instead. A one-third change on either can therefore round back to the same shutter value.

What do the lock buttons do?

They pin one axis so it will not be moved when you change another, and clicking a second time releases it. Use Lock ISO when your camera sits at a base ISO you want to keep, or Lock Shutter to protect a motion-freezing speed.

Is ISO 200 at f/8 the same exposure as ISO 100 at f/5.6?

Yes, at the same shutter speed. Doubling ISO adds a stop and opening f/8 to f/5.6 adds another, so both combinations land at the same brightness. They differ in noise and depth of field, neither of which this calculator models.

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exposure triangle calculatoriso shutter aperture calculatorstops of light calculator

Calcolatore del Triangolo dell'Esposizione (ISO, Scatto, Apertura)

Come funziona il calcolo

Domande frequenti

Conosciuto anche come

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