Elements of Exposure

Exposure

• The amount of light that is allowed to hit the film or the imaging chip in a digital camera

Three Things Control Exposure

• F-stop: Size of lens opening.Amount of light the camera allows in.

• Shutter speed. Length of time the light is allowed into the camera.

• Film Speed: Film sensitivity to light

• You can change any of these as long as you change the other

Exposure

• Measured in increments called stops• Each whole stop is calculated in terms of halving

and doubling• Increasing an exposure by one whole stop will

double the original amount of light. • Decreasing an exposure by one whole stop will

cut the original amount of light in half. • Each of the three variables of exposure, f-stops,

shutter speeds, and film speed are all measured in stops.

Stop

• F-stops, shutter speeds, and film speeds are ALL calculated in stops.

• There is one stop difference between:– f/8 and f/11– 1/60 and 1/125 of a second– ISOs 200 and 400

Shutter Speed

• Like f-stops, whole shutter speeds are spaced one stop apart.

• The longer the duration the more light that gets to the sensor

• That means that a shutter speed of 1/60 lets in twice as much light as 1/125, and half as much as 1/30

•

Shutter Speed1/1000 sec.

1/2 sec. 4 sec.

Aperture and F-Stops

Lens opened up to f/2

Lens stopped down to f/11

F-Stop

• A numerical representation of the diameter of a lens aperture.

• The “f” stands for the focal length of the lens in a fraction.

• The smaller the f-number, the bigger the aperture and the less depth of field.

• The bigger the f-number, the smaller the aperture and the greater depth of field.

F-Stops• The f in f-stop refers to the

focal length of a lens.

• The slash / indicates division

• This means that an f-stop refers to the focal ratio.

• So in the case of f/8 on a 50 mm lens, it means 500mm is divided by 8=6.25mm, which is the physical diameter of aperture opening of f/8 in a 50mm lens.

• This works the same for all f-stops on all lenses.

Lens opened up to f/2

Lens stopped down to f/11

F-Stops

• The numbers are set up so there is a difference of one stop between each whole f-stop number in progression.

• Smaller numbers let in more light. Bigger numbers let in less.

• F/8 lets in twice as much light as f/11, and f/16 lets in half as much light as f/11

Lens opened up to f/2

Lens stopped down to f/11

F-Stops

• Each f-stop number indicates a standard amount of light so..

• f/8 on a 24mm lens lets the same amount of light as f/8 on a 500 mm lens.

Depth of Field• An important part of

every image• Refers to how much

of the scene is in focus, both in front of and behind the subject or at whatever point the lens is focused.

Depth of Field

• The smaller the aperture or opening, the larger the number of the f-stop and the greater the depth of field in the image

• The larger the aperture or opening, the smaller the number of the f-stop and the less depth of field in the image

f/2

f/22

Camera focused on the middle chess piece,the only object in focus with the f-stop of f/2

Camera focused on the middle chess piece,the only object in focus with the f-stop of f/2

Setting the Aperture

Low F-stop3.2

High F-stop16

Short

LongDepth-of-Field

Exposure Mode Controls

Auto (point & shoot)

Program

Shutter priority

Aperture priority

Manual setting

White BalanceWB corrects for different lighting conditions

Controls on LCD from rear panel button

Typical Viewfinder

Flash mode

Macro mode

PicturesRemaining

Zoom Level

Image Quality

Exposure Bracketing

• Allows taking 3 shots at different exposures

• Bracket can be set in 1/3 stop increments

• Exposure range can be set to –2 to +2 stops

- .7 stop Normal exposure +.7 stop

Digital Camera has TWO zooms

• Digital Cameras have:– Optical Zoom– Digital Zoom

• Optical uses the camera’s LENS• Digital zoom uses only a portion of the camera’s

megapixels

(extrapolated means GRAINY!)

W

T

Effects of Digital Zoom

Camera Status Panel