Aperture and Depth of Field

APERTURE (F/STOP) 1. What is it?2. Where is it?3. What does it do?4. When do you use it?5. Why would you use F/2.8?6. Why would you use F/22?

THIS IS APERTURE, Also called an F/stop

Aperture- refers to the opening in the lens

It controls:

- how much light is let in through the lens- Depth of field

Every aperture setting is called an f/stop, or a whole stop of light

To increase the aperture is to open up. Every stop you open up, it lets in twice (or 2x) as much light. (example: if you are at f/8 and open the aperture to f/5.6 you are letting in twice as much light.

To decrease the aperture is to stop down. Every stop you stop down, you let in half as much light. (example: if you are at f/8 and stop down to f/11 you are decreasing the light by half.The standard f-stops you need to memorize are: f/2,f/2.8,f/4,f/5.6,f/8,f/11,f/16,f/22,f/32

If you open up your lens, you must increase your shutter speed. If you stop down, you must decrease your shutter speed.

Aperture also controls the Depth of Field

What is Depth of Field?• A camera can only focus its

lens at a single point, but there will be an area that stretches in front of and behind this focus point that still appears sharp.

• This zone is known as the depth of field. It’s not a fixed distance, it changes in size and can be described as either ‘shallow’ (where only a narrow zone appears sharp) or complete (where more of the picture appears sharp).

Shallow vs. Greater (or complete) Depth of Field?

f/1.8 Shallow depth of field

f/16 Greater depth of field

Shallow Depth of field• The shorter the focal distance you

are from the subject, the shallower the depth of field. You have to be within about 10-15 feet of your subject to get a shallow depth of field

• Good for emphasizing your subject. Or blurring out distracting backgrounds.

• Shallow depth of field is usually f/5.6 and below. The lower the number, or the more wide open the aperture, the more extreme the blur.

• Shallow depth of field lets in a lot of light, the aperture is wide open. So this will affect how fast the shutter speed is. HOW?

What causes that blur?Remember pinhole cameras from the history of photography? Well they have no focusing ability, you cannot adjust the size of the hole, and it has an an infinite depth of field. Everything is equally in focus.

What causes the blur (cont.)• The lens works by bending light so that the rays emitted from any point on the

subject have a larger target to hit, but still form a sharp image on the sensor. So far so good, but there is a cost. In the pinhole camera, all objects are equally in focus. With the lens, the focus must be adjusted for a subject. You tell the lens how far away the subject is, and it will make sure that light radiating from that distance is brought back to a single point on the sensor. The slice of the world that is in focus is called the focal plane.

• So what about objects that are not on this focal plane? Light rays from points on these other objects will still be bent back to a single point by the lens, this point will be slightly in front or behind the sensor. If the object is in front of the focal plane then the light rays will not have enough distance to converge; if the object is behind the focal plane the rays will converge before the sensor and cross over. Either way they appear in the image as a blurred disc the same shape as the aperture.

Examples of a LARGE Aperture- shallow depth of field

Focal distance also affects depth of field. • If your subject is far

away from the camera, the greater (or more complete) the depth of field. You would not be able to get a shallow depth of field no matter what aperture you use.• Mostly used for

landscapes or for subjects you don’t want to have blurring.

Greater or complete depth of field• More parts of the picture are in focus• If everything is in focus it’s considered a complete depth of

field• Complete depth of field is usually higher # f/stops, like f/16 or

f/22• Question: How much light would these f/stops let in?• Answer: not much, it’s a small aperture!• So what happens to the shutter speed then?• Remember, DO NOTlet the shutter speed go under 60!!

What if the shutter speed makes me go under 1/60?• What can you do?• You can use a tripod.• Or bump up the ISO higher, this will allow more light to hit the

sensor, and you can shoot above 1/60 shutter speed. BUT this will result in a poorer quality photo.

ISO

Examples of a SMALL Aperture- complete depth of field(f/22)Good for landscapes and for subjects you want entirely in focus.

You can be close up to a subject and still get a complete depth of field by using f/16 or f/22.

Now it’s your turn…

Shallow Depth of Field or Complete Depth of Field?

Can you have a shallow depth of field with this subject?Why or why not?