Disparai — Camera Exposure and Sunny 16

Disparai — Camera Exposure and Sunny 16 | disparai.com

To expose a photo correctly you combine three settings: aperture, shutter speed and ISO. Each admits or restricts light in a measurable way, and the same exposure can be reached with many different combinations. This guide shows the numbers, the sunny 16 procedure and the exposure value table.

disparai.comEV 0 = 1 second at f/1.0EV 16 = light sand or snow in full sun, ISO 100

Exposure scales and one-stop steps

Standard exposure scales and the effect of one stop
Setting	Typical values	One stop brighter	One stop darker
Aperture	f/1.0 · f/1.4 · f/2 · f/2.8 · f/4 · f/5.6 · f/8 · f/11 · f/16 · f/22	Open one step, e.g. f/16 to f/11	Close one step, e.g. f/16 to f/22
Shutter speed	1 s · 1/2 · 1/4 · 1/8 · 1/15 · 1/30 · 1/60 · 1/125 · 1/250 · 1/500 · 1/1000 s	Double the time, e.g. 1/100 s to 1/50 s	Halve the time, e.g. 1/100 s to 1/200 s
ISO	50 · 100 · 200 · 400 · 800 · 1600 · 3200	Double the ISO, e.g. 100 to 200	Halve the ISO, e.g. 200 to 100
EV 0 reference	1 s at f/1.0	EV 1 = 1/2 s at f/1.0	EV −1 = 2 s at f/1.0
Typical full sun, ISO 100	EV 15	f/16 at 1/100 s	f/11 at 1/50 s
Light sand or snow, ISO 100	EV 16	f/16 at 1/125 s	f/11 at 1/60 s
Sunny 16 for ISO 400	f/16 at 1/400 s	Set 1/500 s on the dial	Open to f/11 at 1/250 s

Standard exposure scales and the effect of one stop

What the three controls each do

Aperture, shutter speed and ISO each change the light reaching the recording medium by a measurable factor of two.

Aperture is the diameter of the opening in the lens, written as an f-number. Moving from f/16 to f/11 doubles the area of the opening and admits twice the light; moving from f/11 to f/16 halves it. The scale runs f/1.0, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, with each step a factor of two in light.

Shutter speed is the length of time the sensor or film is exposed, written as a fraction of a second or as whole seconds. Moving from 1/100 s to 1/50 s doubles the time and doubles the light; moving from 1/100 s to 1/200 s halves both. The series 1/1000, 1/500, 1/250, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 s steps by factors of two.

ISO is the sensitivity of the film or sensor. ISO 200 collects the same image in half the time of ISO 100, so it lets you use a faster shutter or a smaller aperture. Doubling ISO is the same one-stop change as opening the aperture one step or doubling the shutter time.

Aperture controls depth of field as well as light: f/16 gives deep focus, f/2 a shallow plane.

Shutter speed controls motion: 1/1000 s freezes a running figure, 1/15 s blurs it.

ISO controls grain or noise: each doubling makes the image measurably coarser.

Any change in one control can be cancelled by an equal change in another.

Working the procedure

How a camera's meter reads the scene

A camera's light meter measures the luminance of the scene and indicates the exposure settings.

The meter averages the light coming through the lens and returns a pair of aperture and shutter speed that will place a mid-grey tone on the recording medium. It does not know whether your subject is snow or coal; it only reports the luminance it sees.

Because the exposure of a scene can be achieved with many combinations of aperture and shutter speed that admit the same amount of light, the meter's answer is a starting point rather than an order. In aperture-priority mode you fix the f-number and the meter picks the shutter; in shutter-priority mode you fix the time and it picks the aperture.

The sunny 16 rule exists so that you can work without the meter at all. It gives the same answer the meter would give on a sunny day, and it can be checked against the meter as a calibration.

The exposure triangle at a glance

Read the table below to see what each setting controls and how doubling or halving changes the light.

The three settings are coupled: raise ISO and you can close the aperture or shorten the shutter by the same amount. The table gives the standard scales and the direction of change.

Exposure value: one number for the whole pair

Exposure value combines aperture and shutter speed in one number: EV equals the aperture value plus the time value.

Because every f-number and every shutter speed can be written as a value on a powers-of-two scale, their sum is a single figure that describes the exposure independently of how it is split. EV 0 is 1 second at f/1.0. One stop brighter is EV 1; one stop darker is EV −1.

The EV table for ISO 100 places a typical scene in full or slightly hazy sunlight at EV 15 and light sand or snow in the same light at EV 16. Each step of EV is a factor of two in light, so the difference between the two entries is one stop.

Using EV lets you look up a scene once and then choose any pair that matches. EV 15 can be met by f/16 at 1/100 s, by f/11 at 1/50 s, or by f/8 at 1/25 s; all three admit the same light.

EV 0: 1 s at f/1.0
EV 15: f/16 at 1/100 s, typical full sun
EV 16: f/16 at 1/125 s, light sand or snow
Each EV step is one stop, a factor of two in light

Questions photographers actually ask

Do I have to memorise the whole EV table before I shoot?

No — learn two anchor points and work from them. EV 15 is a typical scene in full sun at ISO 100, and EV 16 is light sand or snow in the same light; each step away is one stop, a factor of two.

My camera only shows 1/50 s and 1/60 s — which do I use for the sunny 16 shutter?

Use the nearest marked value; half a stop of error is invisible on film and negligible on a sensor. The rule gives 1/100 s for ISO 100, and 1/125 s is the closest standard marking.

Why does my snow photo come out grey?

The meter averages the scene toward mid-grey, so bright snow is underexposed by one to two stops. Expose for EV 16 instead of EV 15, or open the aperture one step from the meter's suggestion.

Is the sunny 16 rule still useful if my camera has a meter?

Yes, as a check and as a way to pre-set the camera before you raise it. If the meter and the rule disagree by more than one stop, one of them is being fooled by backlight or by a dark background.