f/8 · 30 s — EV 1

The scale is engraved rounded

The engraved numbers give 1.09, a drift of +0.093 — 0 from the aperture and 0.093 from the shutter.

Other combinations at this EV

Cells on the same diagonal put the same amount of light on the film or sensor. The photographs still differ: a wider aperture blurs the background, a slower shutter blurs whatever moves. Only the brightness matches.

Raising the ISO

ISO doubles by the stop as well, so doubling it raises the EV by one: the same aperture and shutter now cover a scene one stop darker.

• ISO 50EV 0
• ISO 100EV 1
• ISO 200EV 2
• ISO 400EV 3
• ISO 800EV 4
• ISO 1600EV 5
• ISO 3200EV 6
• ISO 6400EV 7

Same aperture

Same shutter speed

The equal-EV diagonal

Close the aperture one stop and slow the shutter one stop and the EV does not move. So the cells of equal EV lie along a diagonal. The longest such run is eleven cells; runs get shorter toward the corners of the table.

The Sunny 16 rule

On a bright sunny day, set f/16 and the shutter to one over the ISO. At ISO 100 that is 1/100 s, which is not on the dial, so you use 1/125 s — in this table f/16 · 1/125 is EV 15, and EV 15 is bright sun. Still useful when you have no meter.

How to read it

• EV = log2(aperture² ÷ exposure time). f/1.0 for one second is EV 0.
• Because the scale doubles each step, the EV equals the sum of the two scale positions.
• Close the aperture one stop and the EV rises by one; speed up the shutter one stop and it rises by one.
• Cells of equal EV lie on a diagonal — combinations that pass the same amount of light.
• Doubling the ISO raises the EV by one.
• The engraved numbers are rounded, so computing from them drifts the EV by up to 0.174.