intro to digital photo

Camera

More Camera Functions

• ISO tells us how much light it will take to create the image, setting the relative sensitivity of the digital sensor.

• The higher the number, the less light it takes to make the image.

• It takes twice as much light to make a picture at 200 speed as it does at 400 speed. It takes twice as much light to make a picture at 100 speed as it does at 200 speed.

• 400 iso=x, 200 iso=2x, 100 iso=4x where “x” is the amount of light needed

Gains & Losses

• What you gain with a higher speed setting: ability to take pictures in lower light situations without needing a tripod or a flash.

• What you lose with higher speed settings: resolution - the higher the speed, the more “noise” you have in the image, and the larger the “grain” or dots in your image.

Controlling the Light• The size of the opening is one way to control

the amount of light entering the camera. This is called the F-Stop setting.

• The length of time the shutter is open is the other control on the amount of light entering the camera. This is controlled by the Shutter Speed setting.

F-Stop

• Also known as “aperture”, the f-stop is the opening in the lens where the light enters the camera.

• The F-stop numbers are found by the following equation:

F-stop = focal length of the lensDiameter of the opening

More on F-stop

2 2.8 4 5.6 8 11 16 22

The numbers below are the f-stops on the camera. While the image references a lens from a 35mm camera, the concept is the same in digital.

Note that the smaller numbers correspond to the larger openings

What the numbers mean to the picture . . ..

2 2.8 4 5.6 8 11 16 22

More Light Less Light

Selective Focus(Sel Foc)

Depth of FieldDOF

More appearsTo be in focus

Less appearsTo be in focus

Focal PlaneThe focal plane is the plane on which the camera is truly focused.

The remainder of the picture that “appears” in focus is your depth of field. This can be a shallow depth of field, where only a little bit of distance (depth) is in focus, or great depth of field, where more or all of the image appears to be in focus.

We call a shallow depth of field shot “selective focus” and a great depth of field shot “DOF” .

Note the difference in the amount of the page that is in

focus. The focal plane, or point of focus remains the same, but the distance on the page that appears in focus increases as

the f-stop size decreases (number increases)

ALSO NOTICE that the amount of image area that appears to be in focus is broken up so that you

get 1/3 of the total depth of field in

FRONT of the focal plane and 2/3 of it in

BACK of the focal plane

Red line represents focal plane

FACTORS in Potential Depth OF Field

• The total depth of field will depend on:• Distance from the camera to the focal plane

(how far from camera to what you focus on)• Focal length of the lens: wide angle lenses

have greater depth of field than telephoto. • F-stop: the smaller the opening, the more of

the total potential depth of field will appear to be in focus.

TIPS for the ASSIGNMENTS

• To take a DOF shot it is best to be 10’ or further from your focal plane (subject you focus on)

• To take a Selective Focus shot it is best to be closer than 10’ to your focal plane.

Depth of field Selective Focus

Selective Focus Examples

Depth of Field Examples

Shutter Speed• Shutter speed is literally how fast the

shutter opens and closes.

• This controls the amount of light hitting the digital sensor.

• This also determines whether the image is a “stop action” or “blurred motion” shot.

Shutter SpeedsB 4’ 2’ 1 2 4 8 15 30 60 125 250 500 1000 2000

Shutter speed numbers are fractions of a second. That means that the number 30 is actually a 1/30th of a second exposure. The light will be striking the film for 1/30th of a second. The numbers above are full stops - you may have several more available to you in between these.

The B setting is for BULB, which allows the photographer to make exposures for longer than the last shutter speed available on your camera, which may be as long as 15 or 30 seconds. This is necessary for night photography, or where there is a low level of light, or if the goal is to blur something moving at a relatively slow pace.

It’s All Relative . . .

• The difference between the stop action and the blurred motion shots is the amount of time the object has to register on the film and HOW FAST that object is moving.

• For a STOP ACTION, the shutter speed must be FASTER than the speed of the action.

• For a BLURRED MOTION, the shutter speed must be SLOWER than the speed of the action.

• So how fast is fast???

What the Speeds MEAN

1 2 4 8 15 30 60 125 250 500 1000 2000Tripod is necessary Safe to hand hold the camera

*The shutter speed must be equal to or higher than the focal length of the lens to avoid CAMERA SHAKE.

60 - will stop someone walking

125 - will stop someone running

250 - will stop someone on a bike or skateboard

500 - will stop a horse galloping

1000 - will stop water splashing or the wingsOf a hummingbird

How much blur is that?

• One shutter speed slower than necessary to “stop “ the action will blur it enough to see the blur but still be able to tell what the subject is.

• Two shutter speeds slower than stopped will blur it twice as much.

• Three shutter speeds slower than stopped will blur it 4 times as much - you probably won’t be able to tell what the object is - just lines of motion.

• Four shutter speeds slower and you run the risk of not being able to see the object at all.

Stop Action

Blurred Motion

Extended Shutter Speeds

with a tripod

Proper Exposure is arrived at through:

• Available Light : how much light is there while you are shooting

• ISO : what is the sensitivity setting at which you are shooting (variable)

• F-stop : aperture setting (variable)

• Shutter Speed: (variable)

ReciprocityThe relationship of 1:1

• The integral relationship of F-stop to Shutter Speed is that the combination of both controls is the total exposure.

• What makes this easier, is that one change in F-stop equals one change in shutter speed.

• Each change is referred to as a “stop” of light.

If your meter reading is F-8 at 60, what are other setting combinations that will result in the SAME

exposure?

2 2.8 4 5.6 8 11 16 22

B 1 2 4 8 15 30 60 125 250 500 1000

1. IF you wanted a stop action of a galloping horse, what would your settings be?

2. If you wanted a shot with maximum depth of field, what would your settings be?