曝光值（ISO 100 下的 EV）
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相对基准的差值 Δ： 0 档 · 上次锁定： 无
| 如果你改变… | 为保持曝光一致，请调整… |
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计算原理
每一“档”表示光量加倍或减半。将 ISO 加倍、光圈开大一档，或快门时间加倍，都相当于增加一档。等效曝光需保持 ISO 档数 + 光圈档数 + 快门档数 的总和不变。
ISO 100 下的 EV = log₂(N² / t)，其中 N 为光圈值，t 为快门时间（秒）。我们以 1/3 档为单位调整，以匹配相机拨盘的档位间隔。
📷 摄影
曝光三角计算器（ISO、快门、光圈）
计算光圈、快门速度和ISO之间的等效曝光值。每次点击精确对应一档曝光，支持分档调整并输出EV表。
计算原理
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.
常见问题
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.
别名
exposure triangle calculatoriso shutter aperture calculatorstops of light calculator
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