lenses and aperatures 2014
DESCRIPTION
Information on apertures, ƒ/stops and depth-of-field as related to digital photography and dSLRs.TRANSCRIPT
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 — MacroShallow — Macro
Shallow — MacroShallow — Macro
Shallow — MacroShallow — Macro
Deep — MacroDeep — Macro
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?
RememberYour are to take two exposures
• One deep• One shallow
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
DoF is deep (ƒ/11) Choose new ƒ/stop (ƒ/2.8) ƒ/stop difference
+4 stops Lets in more light
Find new shutter speed
DoF is deep (ƒ/11) Choose new ƒ/stop (ƒ/4) ƒ/stop difference
+4 stops Lets in more light
Find new shutter speed
Finding Reciprocal Exposure Step 3
Find new shutter speed-4 OR -3 stopsLets in less light
New reciprocal (equivalent) exposure ƒ/2.8 @ 1,000 or ƒ/4 @ 2.000
Your Assignment: Example 2
This photo is ƒ/32 @ 60. What should the other photo be taken at?
RememberYour are to take two exposures
• One deep• One shallow
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? Are there any limitations? How would you compensate?
RememberYour are to take two exposures
• One deep• One shallow
Your Assignment: Example 3
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?
RememberYour are to take two exposures
• One deep• Ocne shallow
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?
RememberYour are to take two exposures
• One deep• Ocne shallow
Finding Reciprocal Exposure Ans. #5
New exposure ƒ/4 @ 2,000 (deep)