Digital Photography I The Basics Peter Liu Photography kaiscapes .com

Photography

• From two Greek words meaning drawing with light:

• • phos ("light")

• • graphis ("stylus", "paintbrush")

• Merriam-Webster:

• The art or process of producing images on a sensitized surface (as a film) by the action of radiant energy and especially light.

Photography

• The art of capturing light as it falls on a subject or scene, and rendering it so that your viewer is moved by the result.

Capturing Light

• Hard Light high contrast, well-defined shadows

Capturing Light

• Soft Light diffused, rich colors

Capturing Light

• Overhead Light harsh shadows

Capturing Light

• Front Light flat, lacks dimension

Capturing Light

• Side Light evokes mood, accentuates shapes

Capturing Light

• Back Light may need to fill, makes silhouettes

Capturing Light

• Overcast Light low contrast, muted shadows, good for detail

Characteristics Of Light

• Quality

• • The smaller the light source, the harder the light appears

• • The larger the light source, the softer the light appears

• Direction

• • Determines where shadows fall

• Contrast

• • Difference between the lightest and darkest tones of the subject or image

• Source

• Ambient daylight, tungsten, flourescent, firelight

• Artificial flash, tungsten

• Intensity

• Reflectance

• • Reflectivity of the subject

• • Intensity of the light source

• • Angle of view

• • Distance of light source

• Fall-off

• • Increase distance, decrease light level (Inverse Square Law)

Characteristics Of Light

• Color

• Mixture of primary colors: Red, Green and Blue varies according to source

• Warm predominantly red

• Cool predominantly blue

• Expressed in Kelvin (K):

• • Incandescent ~ 3000K

• • Fluorescent ~ 4100K

• • Flash ~ 5400K

• • Daylight

• • • Direct Sunlight ~ 5200K

• • • Cloudy ~ 6000K

• • • Shade ~ 8000K

• Referred to as White Balance in digital photography.

White Balance 4100K ( Fluorescent ) 3000K ( Incandescent ) 5200K ( Sunlight ) 8000K ( Shade ) 5400K ( Flash ) 6000K ( Cloudy )

Why Are You Telling Us All This??

• Because good photography depends on being able to execute two things well:

• Exposure

• Composition

Exposure

• A combination of three factors sometimes known as the Photographic Triangle:

• Shutter Speed

• Aperture

• ISO

• Or

• how quickly light is being captured through how big an opening onto how sensitive a surface

Shutter

• A cameras shutter covers the hole through which light enters to expose the sensor or film.

The shutter release button causes the shutter to open for a certain amount of time, then close again. Image source: www. howstuffworks .com Image source: VisibleDust

Shutter Speed Fast

• 1/1600 sec., stops action

Shutter Speed Slow

• Silky, cool, edgy effects

1 sec. 3 sec. 1/3 sec.

Shutter Speeds

• Open too long, photos are washed out (overexposed)

• Not long enough, photos are too dark (underexposed)

• Expressed in seconds: 1/8000, 1/4000, 1/2000 1/1000, 1/500, 1/250, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, 1 second, 2 seconds, etc.

• Each setting is half or double the speed of its neighbor.

• As the amount of available light decreases by half, the shutter speed needs to slow by double.

• As the amount of available light increases, the shutter speed needs to increase

Aperture

• The opening through which light enters the camera.

Sometimes called an iris because it imitates the opening in the human eye. Image source: www.howstuffworks.com

Aperture

• The size of the opening is expressed as an f-stop number : 1.42.02.845.68111622

• Each number represents an opening size that is half or double its neighbor

• The larger the number, the smaller the opening

• For all the science types: the f-stop is actually a ratio between the diameter of the aperture in the lens and the focal length of the lens:

• • e.g. f/2 on a 50mm lens says the aperture is 25mm. 50/25 = 2.

• • (Source: A Tedious Explanation of the f/stop by Matthew Cole)

• For the rest of us: the size of the opening controls the depth of field in the photograph.

Aperture And Depth Of Field

• f/5.6

• Shallow depth of field

f/22 Deep depth of field

Aperture And Depth Of Field

• Caused by refraction of the light hitting the edge of the opening

• Rays scatter and overlap instead of going straight on its way to the sensor or film

• The camera sees multiple images, resulting in blur.

• The smaller the opening, the less surface available to scatter the light, resulting in less blur.

• Bottom line: the aperture is used to control how much of the scene is in focus.

Aperture And Shutter Speed

• The following reciprocals will yield the same exposure:

• What changes is how much is sharp and in focus.

1/8 sec. f/22 1/15 sec. f/16 1/30 sec. f/11 1/60 sec. f/8 1/125 sec. f/5.6 1/250 sec. f/4 1/500 sec. f/2.8

The Light Meter

• A device that assesses a scene and figures out the correct exposure

• Modern cameras have them built-in

• External handheld models also available

• Engaged when shutter is pressed halfway

• Matrix/Evaluative, Center-weighted, Spot metering

• Looks for 18% Grey or Middle Grey

• Easily fooled!

Tricky Metering Situations

Exposure Compensation

• Used when the light meter is unable to evaluate the exposure as desired, or when correcting by whole stops is too much

• Usually +/- 2 EV (Exposure Value) in steps of 0.3 EV

• Available on most cameras

ISO

• Sensitivity of the sensor or film to light

• Represented by a number assigned by the International Standards Organization (hence, ISO) 100, 200, 400, 800, etc.

• Again, each number represents double or half the sensitivity of its neighbor (Aint it wonderful!)

• The higher the number, the more sensitive to light

• Digital photography is cool because you can change the ISO from shot to shot!

Higher ISO = More Noise!

• ISO 3200

So

• Exposure depends on:

• Shutter Speed how fast

• Aperture how much

• ISO how sensitive

• And color is a function of:

• White Balance how hot

And

• Which camera you choose is a function of how much you want control those factors!

Cameras

• Two popular types of cameras on the market for the consumer

Point-and-shoot SLR (Single-lens Reflex)

Cameras

• Point-and-shoot

• Viewfinder separate from lens

• Small and compact

• Fixed lens

• Shutter delay

• Usually fully automatic (some exceptions, like Olympus C-series)

• SLR (Single-lens Reflex)

• Based on 35mm design

• Actual image seen in viewfinder

• Interchangeable lenses (more flexible composition)

• Ability to use filters

• More advanced metering and shutter system

• Little to no shutter delay

• Automatic, Program (Scene), Shutter Priority, Aperture Priority and Manual modes

• Flash hot shoe

• Pro models may not have pop-up flash or Program (scene) modes

Point-and-shoot Anatomy

• Viewfinder separate from lens (better to use LCD on digital)

• Actual image (as exposed) is not quite the same as in the viewfinder

• Much simpler design than SLRs.

Light Path Lens Camera Body Viewfinder (front) Shutter Sensor or Film Viewfinder Focal Length LCD Screen (Digital)

SLR Anatomy

• Through-the-lens (TTL) viewing (works like a periscope)

• Actual image (as exposed) is shown in the viewfinder

• Mirror flips up when the shutter release is pressed, exposing the sensor (and blacking out the viewfinder)

• Reflex