Focal Length

ƒ/stops

Depth-of-Field

Selective Focus

Traditional Traditional LensLens

Distance Scale

Depth-of-field Scale

ƒ/stops

Cutaway of LensCutaway of Lens

Lens clipped at mounting site

Why there is not a ƒ/1

Aperture Basics

Located in back of lens (called an iris diaphragm) Opening which light passes through into camera Variable size Written as fraction (ƒ/16)

Focal LengthFocal Length

Distance in mm

A “normal” lens for 35mm is 50mm long

The focal length is the distance from the secondary principal point to the rear focal point of a lens.

Focal Length

Focal LengthFocal LengthWide Angle Lenses Ultra Wide

15mm to 20 mm Normal Wide

24mm to 40mm

24mm

Focal LengthFocal Length

50mm

Normal Lenses 45mm to 55mm

Focal LengthFocal Length

85mm

Short Telephoto 70 mm to 135mm 85mm to 120mm good

for portraits

Focal LengthFocal Length

200mm

Long Telephoto 150 mm to 300mm

Ultra Long Telephoto 300 mm to 1000mm

24mm24mm

50mm50mm

85mm85mm

200mm200mm

Aperture TermsAperture Terms

ƒ/stop ƒ/number  focal ratio f-ratio relative aperture

Lenses Showing AperturesLenses Showing Apertures

1. Wide open, small ƒ/number

2. Closed down, large ƒ/number Remember ƒ/numbers or

ƒ/stops are fractions.

ƒ/Number Formulaƒ/Number Formula

The f-number N is given by formula to right

ƒ is the focal length,

D is the diameter of the entrance pupil (effective aperture).

F-number

The standard f-stop scale where √2(square root of 2) corresponds to the sequence of the powers of: f/1, f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16, f/22, f/32, f/45, f/64, f/90, f/128, etc.

The values of the ratios are rounded off to these to make them easy to remember and write down.

Aperture & ƒAperture & ƒ/stops/stops

Remember ƒ/stops are a fraction of the diameter of the lens. Larger numbers (ƒ/22)

Smaller opening Less light

Smaller numbers (ƒ/2) Bigger opening More light

What do the numbers really mean?

When the lens is set to ƒ/2, the hole in the lens is 1/2 as big as the lens is long.

When the lens is set to ƒ/8, the hole in the lens is 1/8th as big as the lens is long.

Which hole is bigger, 1/2 or 1/8?

Which hose would let more water through, one that's a half inch in diameter or one that's one-eighth in diameter?

Which ƒ/stop lets in more light, ƒ/2 or ƒ/8?

2 2.8 4 5.6

8 11 16 22

1.4

Standard ƒ/stops

ƒ/ 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32, 44, 64

Yellow numbers are uncommon.

1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, 32

Know these numbers.

Small amount of light

Large amount of light -1 stop +1 stop

Controlling

Focus

Depth-of-Field — DoFDepth-of-Field — DoF

The distance in front of and beyond the subject that appears to be in

focus.

Light rays converge through a lens at different distances in front and behind film

plane in a cone.

When a lens is in focus, light rays are sharp on the film plane.

The circle of confusion is the “slice” of the cone at the film plane that is not in focus.

The farther the tip of the cone is from the film plane the larger the circle of confusion.

DoF is the area appearing in focus.

Depth-of-field (DoF)

Shallow DoF

Only subject in focus

ƒ/2, ƒ/2.8, ƒ/4

Deep DoF

Everything in focus

ƒ/11, ƒ/16, ƒ/22

Closer subjects (esp. macro)

Less DoF

Shallow

Distance subjects

Greater DoF

Deep

Shallow & Deep DoF

Shallow

Little in focus

Deep

More in focus

ƒ/5.6

@ 1,000

35 mm

ƒ/16

@ 125

35 mm

Depth-of-FieldDepth-of-Field

Distance Scale

Depth-of-FieldDepth-of-Field

Depth-of-field scale

Depth-of-FieldDepth-of-Field

Use Depth-of-field scale in conjunction with distance scale to tell depth-of-field.

Red area is that in focus at given ƒ/stop. Here is the ƒ/2 reading, 4 feet is the only area in

focus.

Depth-of-FieldDepth-of-Field

View from above. Red area is in focus at given ƒ/stop. Here is the ƒ/2 reading, 4 feet is the only area in focus.

Depth-of-FieldDepth-of-Field

Side View Red area is in focus at given ƒ/stop. Here is the ƒ/2 reading, 4 feet is the only

area in focus.

Depth-of-FieldDepth-of-Field

Red area is in focus at given ƒ/stop. At ƒ/8, area in focus is between 3.5

and 5 feet.

Depth-of-FieldDepth-of-Field

View from above. Red area is in focus at given ƒ/stop. At ƒ/8, area in focus is between 3.5

and 5 feet.

Depth-of-FieldDepth-of-Field

Side View Red area is in focus at given ƒ/stop. At ƒ/8, area in focus is between 3.5

and 5 feet.

Depth-of-FieldDepth-of-Field

Red area is that in focus at given ƒ/stop. At ƒ/16, area in focus is between 3 and 7

feet.

Depth-of-FieldDepth-of-Field

View from above. Red area is that in focus at given ƒ/stop. At ƒ/16, area in focus is between 3 and 7 feet.

Depth-of-FieldDepth-of-Field

Side View Red area is in focus at given ƒ/stop. At ƒ/16, area in focus is between 3 and 7 feet.

Depth-of-FieldDepth-of-Field

Red area is that in focus at given ƒ/stop. At ƒ/22, area in focus is between 2.5 and

14 feet.

Depth-of-FieldDepth-of-Field

View from above. Red area is that in focus at given ƒ/stop. At ƒ/22, area in focus is between 2.5 and 14 feet.

Depth-of-FieldDepth-of-Field

Side View Red area is in focus at given ƒ/stop. At ƒ/22, area in focus is between 2.5 and 14 feet.

Depth-of-Field & Point of Depth-of-Field & Point of FocusFocus

The distance scale changes with the focus. Red line in the center is the point in focus. At ƒ/2, area in focus 3 feet.

Depth-of-Field & Point of FocusDepth-of-Field & Point of Focus

The distance scale changes with the focus. Red line in the center is the point in focus. At ƒ/2, area in focus is just over 6 feet.

Depth-of-Field & Point of Depth-of-Field & Point of FocusFocus

The distance scale changes with the focus. Red line in the center is the point in focus. The translucent red box is the area in focus. At ƒ/22, area in focus is from 3 feet to infinity.

Depth-of-Field & Point of FocusDepth-of-Field & Point of Focus

Red, focus @ 4 feet.

At ƒ/22, area in focus is between 2.5 and 14 feet.

Green, focus @ 6 feet.

At ƒ/22, area in focus is between 2.5 feet and infinity.

Central Point of Interest & Selective Central Point of Interest & Selective FocusFocus

Point of

Focus

Blurred Blurred BackgroundBackground

Eye goes to focused area

BlurredBlurredBackgroundBackground

Eye goes to focused area

Blurred BackgroundBlurred Background& Foreground& Foreground

Eye goes to focused area

Selective Focus

Only Subject in Focus•Foreground blurry•Background blurry

ƒ/5.6

@ 500

400 mm

Selective Focus

Only Subject in Focus•Background blurry

ƒ/8

@ 250

90 mm

Macro

Selective Focus

Only Subject in Focus

•Background blurry

ShallowShallow

ShallowShallow

ShallowShallow

ShallowShallow

ShallowShallow

Shallow — MicroShallow — Micro

Shallow — MicroShallow — Micro

Shallow — MicroShallow — Micro

Deep — MicroDeep — Micro

DeepDeep

Foreground

Mid ground

Background

DeepDeep

DeepDeep

DeepDeep

Deep DoF

ƒ/8

32 mm

Deep DoF

ƒ/9.9

24 mm

DeepDeep

DeepDeep

Think About

Point of Focus (where camera focus is at) Exposure

Choose priority○ Stopping action/showing motion (shutter speed)○ DoF (ƒ/stop)

ShallowDeep

Think how will…○ Shutter speed effect DoF○ DoF effect shutter speed

When you take a photo you should always consider:

Think About

Fast shutter speed means low ƒ/stops Slow shutter speeds means high ƒ/stops Remember: reciprocity (if you change ƒ/stop you must

change shutter speed)

Conversely High ƒ/stops (deep DoF) means slow shutter speeds Low ƒ/stops (shallow DoF) means fast shutter speeds Remember: reciprocity

In General:

Your Assignment: DirectionsDirections You are to take 8 sets of 2 photos (16 photos total)

demonstrating shallow and deep depth-of-field. Each set consists of: Identical photos with the same exact content and focus. Five similar items in a row. The only change should be the ƒ/stop with the exposure

adjusted (±0) so the exposure is reciprocal between the two.

One photo should be with an ƒ/stop less than ƒ/4 (or as low as you can get i.e. ƒ/5.6).

The other photo should be with an ƒ/stop greater than ƒ/11 (ƒ/16+ better).

Remember to adjust shutter speed and/or ISO when changing ƒ/stop. All photos should have reciprocal exposures.

What to turn in Worksheet fully filled

out Contact sheet fully

labeled with exposures

One set of favorite photos printed out w/exposures

Aperture & ƒ/stop rubric

Your Assignment: Example

ƒ/4.3 @ 60 @ 400 ISO ƒ/16 @ 60 @ 1600 ISO

Your Assignment: Example

ƒ/4.3 @ 60 @ 400 ISO ƒ/16 @ 60 @ 1600 ISO

Your Assignment: Example

ƒ/4 @ 250 @ 400 ISO ƒ/22 @ 60 @ 3200 ISO

Your Assignment: Example

ƒ/4 @ 60 @ 400 ISO ƒ/11 @ 60 @ 3200 ISO

Your Assignment: Example 1

This photo is ƒ/11 @ 60. What should the other photo be taken at?

Finding Reciprocal Exposure Step 1

First think about type of DoF (shallow or deep) Find the equivalent exposure for opposite DoF

Finding Reciprocal Exposure Step 2

In this case DoF is deep (ƒ/11) Choose new ƒ/stop (ƒ/2.8) Count difference between ƒ/stops

+4 stops Lets in more light

Find new shutter speed

Finding Reciprocal Exposure Step 3

Find new shutter speed-4 stopsLets in less light

Shutter speed @ 1,000 New equivalent exposure ƒ/2.8 @ 1,000

Your Assignment: Example 2

This photo is ƒ/32 @ 60. What should the other photo be taken at?

Finding Reciprocal Exposure Ans. #2

New exposure ƒ/5.6

@ 2,000

Your Assignment: Example 3

This photo is ƒ/4 @ 125. What should the other photo be taken at?

Finding Reciprocal Exposure Ans. #3

New exposure ƒ/22 @ 4But can only go to 60 so…

ƒ/16 @ 60Not a shallow DoF

Will not work for assignment

Finding Reciprocal Exposure Ans. #3

New exposure ƒ/22 @ 4But can only go to 60 so…

ƒ/16 @ 60Not a shallow DoFWill not work for assignment

Your Assignment: Example 4

This photo is ƒ/8 @ 250. What should the other photo be taken at?

Finding Reciprocal Exposure Ans. #4

Neutral DoF @ ƒ/8, need to make adjustment New exposure ƒ/16 @ 60 (deep) New exposure ƒ/2.8 @ 2,000 (shallow)

Your Assignment: Example 5

This photo is ƒ/16 @ 125. What should the other photo be taken at?

Finding Reciprocal Exposure Ans. #5

New exposure ƒ/4 @ 2,000 (deep)