lenses & exposure · • depth of field • lens speed • ... motion blur. stop action....

• Lens Options• Depth of Field• Lens Speed• Telephotos• Wide Angles

• Light Control• Aperture• Shutter• ISO• Reciprocity

Exposure

LensesLenses & Exposure

The Viewfinder Camera

Image Sensor

viewfinder

aperturelens

shutter

LensBasics

• What is a lens• Focal Length (for 35mm)• Focus, Sharpness, Distortion• Zoom Magnification 1x - 3x - 10x• Lens Size• Glass or Plastic• Macro Focus Lenses

ApertureThe aperture controls the amount of light passingthrough the lens.

f/stops indicate the size of the aperture.Each setting is doubles the light volume admitted.

… 32 – 22 – 16 – 11 – 8 – 5.6 – 4 – 2.8 …

most lenseshave 7 f/stoprange

Depth of Field

Background

Foreground

In focus

Out of focus

Out of focus

Center

Lens Depth of Fieldsubjectcamera

1/3 2/3Area in focus

Depth of field dependson lens focal lengthand aperture setting.

Smaller apertures (f/16-22)provide greater DOF

DOF can bepreviewed onmany SLRcameras.

Wide angle Lenses have greater DOFTelephoto Lenses have less DOF

Depth of FieldControl

Out of FocusBackground popsForeground object

Depth of Field -- ApertureLens TypeOpen Aperture Closed Down

Telephoto Lens

Normal Lens

Wide Angle Lens Full Focus

Long DOF

Medium DOF

Medium DOF

Long DOF

Short DOF

Wide Angle LensesThey Stretch Space – apparently distorting perspective

It is called Wide-Angle Distortion

Use short focal length lensesGet close to the subjectShoot at odd angles

For maximum effect

Wide Angle Lenses

They stretch space

Telephoto Lenses – Flatten Space

Lens Speed – Fast Lenses

• A Faster LensGathers more light

• They have larger“wide open” apertures

• They allow shootingwith smaller ISO &faster shutter speeds

• They are expensive

Lens Hoods – Critical EquipmentThey improve image contrast & sharpnessThey help prevent flare & sunspots

SunspotsOctagonalshaped spotsfrom lightfalling directlyon lens

FlareWashed outareas in theimage from lightbouncing intothe lens.

Shutter SpeedShutter speeds double for each setting

… 1/60 – 1/120 – 1/250 – 1/400 – 1/800 …

Each doubling reduces the amount of light byone half.

Bulb – The shutter will remain open as long asthe shutter is pressed.

Time – Press once to start, again to end.

Motion blur Can create Impact

Slow shutter speeds create motion blur.

Shutter SpeedSlow Shutter Fash Shutter

Stop ActionMotion Blur

Subject Moderate Blur Extensive Blur

Traffic Trails 30 sec 90 sec

Waterfall 1/5 sec 1 sec

Person Walking 1/30 1 /4

Person Running 1/60 1/15

Horse Trotting 1/30 1/8

Car @ 40 mph 1/125 1/30

Car @ 70 mph 1/250 1/60

ISO Speed“Sensor speed = sensitivity to light measuredAs an index number called ISO speed.

50 – 100 – 200 – 400 – 800 – 1600 – 3200

Fast Slow

Less noise More noise

ISO speed

2002, Mike Blevins

Exposure

The aperture -- Controls depth of field

The total amount of light falling on the sensor

The shutter – Controls image motion

ISO Speed – Controls image noise.

Reciprocity – A change in either of these canOffset a change in the other

Camera Exposure Controls

1. Automatic Exposure Control

3. Semi-automatic Exposure Control

4. Manual Exposure Control

• Camera computer sets everything

• You set aperture or shutter

• You set everything

2. Scene Mode Controls• Scene Selection sets Everything

Scene Mode – Easy Exposure Adjustments

Portrait Mode

Landscape ModeSports Mode

Macro Mode

Night Mode Setting the scene tells the Camera what settings to use

END – Section 1

TRIPODS• Improve Image Sharpness• Allow Dawn & Dusk Shots• Architecture & Interiors• Better Portraits• Allows Small f/stop Landscapes• Needed for Long Telephotos

THE TRIPOD RULE:The minimum shutter speedneeded for a sharp negativeIs the reciprocal of the lensFocal length.

250 mm = 1/250 sec400 mm = 1/400 sec

Tripod Features

Consider:• Gitzo - carbon fiber, • Slik - low cost• Cullman (fold flat &monopod)

• Sturdy but strong, 5’-high, 2’-folded• Light – carbon composite is best• Quick release head • Pan-tilt or ball head• Level (bubble)• Under tripod extension

Heads:• Gitzo offset ball• Slik small balls

Other Support Options:• Monopod – hiking stick• Bean Bag – transport unfilled (add beans/sand)• Minimal table top tripod• Shutter release cable or IR remote

Gear Bags:• Backpack & belt mounted lens bags• Lowepro backpacks are the most popular• Hard case with foam inserts• Photographer’s vest• Traditional carry case with straps

Lighting Issues

• Separate electronic flash• match to your system• Rotating & swivel head• Adjustable flash angle• Diffusion add-on• External cord – to move light • Lithium Batteries

• Reflector• folding cloth• cardboard/foil

• Pop-Up Fill Flash,Use it frequently

Using Fill Flash

Even a small camera-mountedfill flash will illuminatefaces that would otherwise be dark.

The exposure metersets exposure for thetotal scene and theface is underexposed.

Filters – To Control Light at the Lens

The Basic Kit (for film cameras)• Skylight, UV, or Haze (on all lenses)• Circular polarizer (good quality • 81A and 81B Warming Filter• Neutral Density (1stop, 2stop, 3stop)• Graduated (clear to ND: 2x, 4x, 8x stop)• Color Graduated (Blue, Brown, etc.)• Yellow, Orange, or Red for B&W

Polarizers – (use Circular on AF Cameras)• Saturates colors, (blue sky – pops clouds)• Reduces or eliminates reflections (water, glass, etc)• Can act as ND filter (1-2 f/stops)• Not great for skin tones, overused.

For DigitalYesYes*YesYes ***

* There is a Photoshop work around

Cokin Graduated Gray Filters

Filters are square which allows splitting the filtersin the holder to get different effects.

Cokin offers are variant of the normal filter systemwith several advantages.

There are over 60 filters in their system.

With GraduatedND Filter

Without Filter

BlockExposureby 2 stops

NormalExposure

Use of Graduated ND Filters

Beach withoutGraduated NDFilter

Beach withGraduated ND Filter

Lenses & Exposure• Lens Options• Depth of Field• Lens Speed• Telephotos• Wide Angles

• Light Control• Aperture• Shutter• ISO• Reciprocity