In photography, the Sunny 16 rule (also known as the Sunny f/16 rule) is a method of estimating correct daylight exposures without a light meter. Apart from the obvious advantage of independence from a light meter, the Sunny 16 rule can also aid in achieving correct exposure of difficult subjects. As the rule is based on incident light, rather than reflected light as with most camera light meters, very bright or very dark subjects are compensated for. The rule serves as a mnemonic for the camera settings obtained on a sunny day using the exposure value (EV) system.

The basic rule is, “On a sunny day set aperture to f/16 and shutter speed to the [reciprocal of the] ISO film speed [or ISO setting] for a subject in direct sunlight.” For example:

On a sunny day and with ISO 100 film / setting in the camera, one sets the aperture to f/16 and the shutter speed to 1/100 or 1/125 second (on some cameras 1/125 second is the available setting nearest to 1/100 second).

On a sunny day with ISO 200 film / setting and aperture at f/16, set shutter speed to 1/200 or 1/250.

On a sunny day with ISO 400 film / setting and aperture at f/16, set shutter speed to 1/400 or 1/500.

As with other light readings, shutter speed can be changed as long as the f-number is altered to compensate, e.g. 1/250 second at f/11 gives equivalent exposure to 1/125 second at f/16.

An elaborated form of the Sunny 16 rule is to set shutter speed nearest to the reciprocal of the ISO film speed / setting and f-number according to this table:


Lighting Conditions 

Shadow Detail 



Dark with sharp edges 





Slight Overcast 

Soft around edges 



Barely visible 


Heavy Overcast 

No shadows 


Open Shade/Sunset 

No shadows 

Add One Stop 



from Wikipedia






Learning what all those buttons and dials do. Cameras can initially be very intimidating. But learning the basic operation of one’s camera will mean better photographs and less frustration.

While this article will cover the basics of camera operation, one should read their camera manual as cameras vary in how they operate.

Rule #1 is always have your camera’s manual available.

Generally, four factors can be varied. These are the lens (focal length), the lens opening (aperture), the shutter speed, and ISO ( a measure of the sensitivity to light). I’ll explain each variable and suggest when each is more important..

Two types of camera are most common today. These are the Point and Shoot and the Single Lens Reflex (SLR) cameras. The capabilities of each can vary widely.

The Lens – A major difference in the two types is that a SLR camera has interchangeable lenses; a Point ans Shoot camera does not. However, while one can change from a close-up lens to a telephoto lens on a SLR camera, many Point and Shoot cameras have zoom lenses. Caution.. Ignore digital zoom. Only optical zoom matters when evaluating Point and Shoot cameras.

The focal length of a lens determines what the camera “sees”. A short focal length lens allows a wide field of view. They are useful when the subject of the photograph is close to the camera. A long focal length lens has a narrow field of view but magnifies distant objects. Zoom lenses allow one to vary the focal length.

The Aperture – The lens opening controls the amount of light that reaches the recording medium, both film and digital sensor. Lens openings are measured in f stops. A small number such as f2.0 is a large opening. A large number such as f22 is a small opening. Obviously, a large opening lets in more light and a small opening less light. The other important difference is that a large opening has less depth of field. Depth of field is a measure of how sharp an image is from front to back. For example is one is taking a portrait type photo, it is helpful to have the background out-of-focus (slightly blurred). The effect is to cause the viewer to look primarily at the portrait and ignore any distraction in the background. Another important factor is when one is recording action and one wants the object to be sharp, An f value of 2.6 allows for a shorter exposure time that results in a sharper image of the object in motion. Conversely, one may want to a blur effect that conveys motion. An f stop of f11 or f`16 means a longer exposure time. The result is the background is sharp and the subject is blurred.

The Shutter Speed – Shutter speed is a measure of how long the film or sensor is exposed to light. It has a reciprocal relationship to the aperture. Long shutter speeds allow one to use a small aperture. Conversely, short shutter speeds require a larger aperture. The same amount of light can enter by adjusting the ratio of shutter speed to aperture. Stopping motion requires a high shutter speed; maximum depth of field (focus) requires a small aperture (high f number).

ISO or Film Speed – The ISO (International Standard Organization) value refers to how sensitive the film or the sensor are to light. A higher ISO number means more sensitivity. With a film camera one is limited by the ISO value of the film in the camera. Digital cameras allow the user to reset the ISO for each photograph. Higher ISO values are generally available with digital cameras; thus one can take photographs in with less available light.

Which setting should one use? Both types of digital camera generally allow one to set a preference and then the camera automatically adjusts other parameters. Typical settings include the following choices.

Program (P) Mode – Program mode allows the user to have the camera set both aperture and shutter speed. Digital cameras are a special type of computer. Based on what the camera is sensing, it sets the values for shutter speed and aperture based on values calculated from thousands of test images that have been stored in the camera’s memory.

Aperture Priority (A) Mode – Aperture Priority allows the user to set the aperture (lens opening) and the camera then calculates the shutter speed necessary for a proper exposure based on the ISO value of the sensor and the amount of light entering the camera. Aperture is important when one wants to ensure the depth of field or wants a wider angle of view.

Shutter Priority (S) Mode – The Shutter Priority mode means the user will set the shutter speed and the camera will set the appropriate aperture for proper exposure. This setting is important if one wishes to “freeze” action such as when taking photographs at a sporting event.

Manual Mode (M) Mode – Using Manual Mode allows the user to set both Aperture and Shutter Speed independent of each other and independent of the ISO value. In addition, the user manually sets the focus point of the subject.

This article is about basics. Many camera also have other settings, The most important is White Balance (WB). The type of light that is exposing the sensor varies in its characteristic. Sunlight is different from artificial lights. The time of day affects the characteristics of sunlight. There are many types of artificial light; tungsten, various fluorescent lights, flash lamps, etc. They particularly affect how the sensor will record colors. Many cameras allow the user to have the camera determine the best white balance.

Finally, settings such as Night Mode, Portrait Mode, Black and White Mode, may be available on your camera. Each of these settings allow the camera to set aperture and shutter speeds based on the information stored on the camera’s internal memory.

Remember, read the manual for your camera. And have fun with your photography.