The lens

Barbara Bosworth Salmon, 1994

& DEPTH OF FIELD

Before we discuss depth of field, lets take a quick look at the general

purpose of a lens.

Light must be controlled if our eyes or our cameras are to form images of objects.

This drawing shows light rays that are uncontrolled. If they were to hit the film in their jumbled state the resulting image would be an unfocused blob.

If you wear eye glasses, take them off. Blobs right? What you just did was take away your light controlling device. The lens!

Film

A lens controls and focuses light by bending the light rays.

This bending of light rays is called refraction.

Uncontrolled light A lens is used to gather & focus the light

Now let’s move on to depth of field

Depth of field

Part 1

Johnny and a the mountain

Imagine…

…a field, any kind of field you want…hay, wheat, flowers. There is a mountain in the background. There are flowers in the foreground and middleground.

Now, Let’s pick a subject to put in the field-Say… Johnny Depp (or whoever you want to imagine…

BTW:This is what kind of DOF?

(But what if you want to really focus on Johnny?)

You might:

Adjust your f-stop… but which way?

You could simply move closer to Johnny (I like this idea)

This would be called Distance to Subject

Or even…

So…When you are going to photograph something, think about what is in front of them or behind

them. Does it add or detract from the subject? What do you want in focus?

Your decision will determine whether you have many elements in focus or just one.

This is depth of field

• the amount of acceptable focus in a photograph

• the area between the nearest and farthest points from the camera that are acceptably sharp in an image.

def. depth of field:

There are 2 types of depth of field:

Shallow*Great/ Broad

*Keep in mind that great does not mean wonderful or good. Think of it as deep focus…everything from the front to the back in the image is in focus.

Elliot Erwitt New York, 1946

Great depth of field

Karl Baden Amelia, 1995

Great

Jack Dykinga Mojave National Preserve, California

Activity:

Working in teams of two or individually:

Using post-it notes or a marker, please label each imageEither “shallow” or “great”.

Tape them on the white board.

Using magazines, find…

2 examples of great depth of field and2 examples of shallow depth of field.

*please find the best examples you can

*controlling what is in focus in your images

*Controlling depth of field

Part 2

There are 3 ways to control dof:

1. Lens focal length (how your lens sees)

2. Camera to subject distance (how far away your main subject is from the camera)

3. Lens aperture (how big or small the hole in the lens is)

Let’s begin with lens focal length

Focal length refers to how much a lens sees.

There are four general types of lenses:

1. normal

2. wide angle

3. telephoto

4. zoom

This drawing shows the angle of view of different focal lengths

Focal length degrees

A normal lens for a 35mm camera sees just like your eye does. There is no or little distortion.

50mm lens

28mm lens

A wide angle lens, (a.k.a. a short lens) sees more than what your eye typically sees.The view is widened and objects appear smaller.

85mm lens 300mm lens

Telephoto lenses (a.k.a. long lenses) see far away objects close-up. They magnify the object so it appears larger than it really is.

Zoom lenses basically have all three of the other types built into them. Zoom lenses are nice because you can pick which focal length or angle of view you want.

28-85mm zoom

The disadvantage of zoom lenses is that they don’t have large apertures so you need plenty of light to use one.

So how is dof affected by the lens focal length?

Here’s the rule:

The shorter the lens ( like a 17 or 28mm lens)The greater the dof.

The shorter the lens ( like a 17 or 28mm lens)The greater the dof.

The second technique to control dof is using camera to subject distance.

The rule with this one is…

The farther away the camera is from the subject the greater the dof.

The farther away the camera is from the subject the greater the dof.

The last technique to control dof is by using the lens aperture.

The rule with this one is…

The smaller the aperture the greater the dof.

The smaller the aperture the greater the dof.

So let’s review how to control…

depthof

field

Focal length

Camera to subject distance

Aperture size

Questions ?!

Now…on to the assignment.Tomorrow!