Digital Photography Photo Organization September 13

Digital Photography

Photo Organization

September 13

Week 2 2

Checkpoint

• Signed Camera Check Out Form• Brainstorm notes

Think about what types of images you may take Think about when you may take them Think about how you may edit them in class Keep in mind that you may take several thousand photos this

semester, and may have several saved versions of each

Week 2 3

Organization

• Let’s discuss what we came up with We can always use somebody else’s ideas for

this, if we like it better than the way we did it!

• You guys have it much easier for organization than past classes, because Adobe CS2 offers a lot of cool stuff Note: only the black computers have CS2, not

the silver ones

Week 2 4

Adobe Bridge

Week 2 5

Adobe Bridge

• Views: Thumbnail Filmstrip Details (Versions and alternates)

• For all these views, you can change size of image displayed

Week 2 6

Metadata

File PropertiesIPTC Core - Standard bunch of metadata for filesCamera Data

Week 2 7

Keywords

• Some pre-defined keywords, but the user has complete freedom in choosing Keyword Sets and

individual keywords

Week 2 8

Ranking

• Built-in easy way to rank images

• Select an image and the dots beneath the image are selectable and change to stars, based on your choices

Week 2 9

Other Features

• Rotation of images

• Labeling

• Filtering (based on rank or labels)

• Find - can base it on several criteria

• And more!

Week 2 10

Lab Time

• You can begin to use Bridge To set up your organization structure To rotate any images To identify and delete any “out-takes” To assign rankings, keywords, etc

• Have fun, but begin a solid structure that you can build upon

Week 2 11

Homework

• Read Chapter 2

• We will discuss tomorrow & Thursday in class

• It is difficult material!

Light and Sensors

Lecture 04

September 14, 2005

Entering complex material…

MDP Chapter 2

Week 2 14

Photography is about light

• Photography = “to write with light”

• So we have to understand a little about light to understand how cameras work

Week 2 15

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

How we see light

• White Light (from the sun) is made up of colors, and each light has a certain wavelength

• Light waves are either reflected, absorbed, or transmitted – which is determined by the object that the wave hits The color we see is based on the type of light sent to

our eyes An apple is red because it reflects red light For an objects to be black, all wavelengths of light are

absorbed, no light is reflected• The primary colors of light are red, blue and

green (we will talk more about this later)http://imagers.gsfc.nasa.gov/ems/visible.html

Week 2 16

How a camera takes a picture

• A camera is like our eyes – to “see” color, it must be able to capture the light that is reflected from objects

• Reflected light enters the camera – passing through the lens’s glass (which may have many elements)

• This light gets focused onto a sensor• The sensor is sensitive to light, so it captures the light

and stores it – creating the image

Week 2 17

What happens inside the camera

Week 2 18

After light hits sensor

• Allows viewing of image on viewfinder or LCD Viewfinder

• can roughly match what sensor sees• Could be like a mini tv• Might be a reflection of the light from the lens

• Push the shutter release button – the shutter opens/closes for a period of time Camera may autofocus, lock exposure, cause flash to fire, etc

• Digital information is stored on memory – the speed that it takes to write the information to memory depends on size of image, type of compression & compression ratio, and speed of media)

Week 2 19

Sensors and colors

• Sensors can’t see colors – they can only collect the brightness of the scene

• Colored filters are used to limit range of light for each pixel So each pixel reads a value for the red, green, or blue to define the final

color – sometimes only one color is read, and the others need to be interpolated

Different sensor types have different ways that they deal with this limitation

Week 2 20

How a sensor works

• The sensor is sensitive to light, so it captures the light and stores it – creating the image – how does this work?

• Sensor is made of millions of individual light sensitive pixels (diodes) This sensors are arranged in a grid, or array

• Each pixel collects a charge proportionate to the intensity and amount of light Pixels translate light into specific voltage values

• The strength of the charge corresponds to the brightness of the pixel (up to a certain point) A pixel can only hold so much charge, if too much builds up, it could

overflow to neighboring pixels – a process called blooming – proper exposure will eliminate most blooming, if in doubt, underexpose the image

Some sensors have mechanisms built in to minimize effects of blooming

Week 2 21

What happens with the charge?

• Light has been collected as voltage (charge)

• Voltage information has an infinite amount of variation, smooth transitions This is called ANALOG information

• The camera needs the information to be in discrete digital numbers to store the picture

• So the sensor (or other circuitry) has to perform analog to digital conversion

Week 2 22

Digital Data

• The digital data can be written to the cameras memory, and represents the light information that hit the sensor, but in a way a computer can understand.

• The image sensor determines the resolution and quality of the final image (by the number of light-sensitive pixels that collect information)

Week 2 23

Types of Sensors

• Sensors work by having light-sensitive pixels that collect the light

• This sensor technology is relatively new (within the last 30 years) and is still being improved.

• Physicists are working with different materials and making different kinds of sensors that capture the light

Week 2 24

CCD Image Sensor• CCD = Charge Coupled Device • Grabs part of picture with each exposure

Array arranged in mosaic or Bayer pattern Each pixel registers one of 3 colors

• 50% green pixels are registered, 25% (each) blue and red registered

• Other colors must be interpolated (guessed) True resolution of camera is reduced because not

all the light is being recorded

• Array of pixels gather light and translate to a voltage CCD sensor is just an analog device – it does not

process voltage; so additional circuitry in the camera must do that

Each row read one at a time (like a conveyer belt)

Week 2 25

Foveon CMOS Image Sensor

• CMOS = Complementary Metal Oxide Semiconductor • Captures RGB light at each pixel; no interpolation (3 layers of

photodetectors) Uses properties of silicon to register light absorption at different

layers No interpolation is necessary – less light is wasted But sensor is less sensitive, so information is still lost

• Pixels in sensor include the circuitry to convert voltage to the digital data done in parallel – each pixel can be processed individually and

immediately Can record an image more quickly (theoretically) Use less power because several functions are included on the

image sensor

Week 2 26

Which image sensor is better?

• Currently, CCD has better image quality and a better range But like we said, it doesn’t do digital conversion, so it

uses more power It requires special production techniques – but

generally has less noise

• But, CMOS is catching up & is being used in professional level cameras because the sensors consume less power CMOS sensors are less expensive to produce

Week 2 27

Tomorrow

• Tomorrow we will look at how lenses affect what light reaches the sensor – and how that affects what image the camera sees.

Lenses and Exposure

Lecture 05

September 15, 2005

Week 2 29

The Lens

• Lens is the eye of the camera It captures and focuses the light onto the sensor

• The lens affects the quality of the image & the kinds of pictures that you can take

• What matters: Quality of lens Amount of light it can

transmit Focusing range Amount of magnification

Week 2 30

Lenses: Focal Length

• Focal Length: The distance from the rear nodal point of the lens to the point where the light rays passing through the lens are focused onto the image sensor Measured in millimeters (Film standard is 35mm) Think of it as the amount of a lens’s magnification

• The longer the length, the more the lens will magnify the scene

Picture from Real World Digital Photography Book

Week 2 31

Focal Length

Photos from Canon WebsiteCanon Photo Shooting- Techniques(Using a telephoto lens)

Week 2 32

Lens Aperture

• Size of the opening that admits light to the sensor, relative to the magnification or focal length of the lens

• f-stops (denominators of fractions indicating relative size of opening) Each stop you open up doubles the amount of light reaching the sensor

• Maximum aperture – lets in more light – good for dim lighting • Minimum aperture – how much light can you block from the sensor (used for

bright lighting) Also can increase depth-of-field

f2f4f8

Week 2 33

Lens Speed

• Lens Speed Amount of light the lens transmits at maximum

aperture A lens with maximum aperture of f2 is “fast”

compared to a lens with max aperture of f8 which is “slow”

• Fast lens = large aperture - allows lens to transmit more light

• Slow lens = small aperture - little light gets through

Week 2 34

Kinds of Lenses

• Zoom Lens Allows you to enlarge or reduce an image without having to get closer or

farther away Optical Zoom - changes the effective focal length of the lens

• Telephoto lens Compresses the apparent distance between objects, making them

appear to be closer together

• Wide-angle lens Expands apparent distance between objects, giving vast areas of

foreground, making distant objects appear to be farther away

Week 2 35

Wide vs. Telephoto Lenses





photo with a wide-angle lens (35 mm)

a photo with a telephoto lens(equivalent to 150 mm)

Photos from Canon WebsiteCanon Photo Shooting- Techniques

Week 2 36

Wide-angle lens

• Wide angle lenses let you shoot over a wide range (vertically) But it makes things in the background appear

even further away (large depth-of-field)

• It can cause strong distortions in up-close photos of subjects






Week 2 37

Telephoto Lens

• Lets far away objects appear closer

• Makes background objects appear to be close to subjects

• Can be used to artistically blur the background (short depth of field)






Week 2 38

Shutter Speed

• Is measured in seconds or fractions of a second

• The duration of time the shutter opens and closes during an exposure process How long the light flows through the lens and

onto the image sensor

Week 2 39

Introduction to Exposure • Exposure is the amount of light striking the sensor• Three factors determine correct exposure

Amount of light in scene that strikes the image sensor Length of time the sensor is exposed to light Sensitivity of the sensor

• Think of each pixel on the sensor as a little bucket that catches photons of light as they pass through the lens. Bucket must fill up to a threshold point before the pixel will

register it as part of the image• Raising or lowering the threshold mark will decrease or increase the

sensitivity of the sensor

Week 2 40

Exposure

• Aperture (f-stop) determines how many photons are admitted at once (like a funnel)

• Shutter speed determines how much time the photons have to strike the sensor (like a valve controlled by a timer)

Aperture & shutter speed work together to create proper exposure–Buckets can be filled quickly with short shutter speed and large lens opening–Buckets can be filled slowly with long shutter speed and small lens opening

Same exposure (same amount of light reaching the buckets) RECIPROCITY – equivalent exposure values

Week 2 41

Reciprocity

• Equivalent Exposures

EV14Shutter f-stop

1/30th sec f22

1/250th sec f8

1/1000th sec f4

1/4000th sec f2

Week 2 42

Schedule

HW1 -- (For Friday, but bring on Tuesday) Write 1/2 - 1 page (single-spaced) OR make a PowerPoint presentation

of a mini biography of a famous photographer (not Ansel Adams), plus download or bring in 2-3 pictures taken by that photographer to show the class on Tuesdat

Tomorrow no coordinate classes this period.

• HW2 - Friday during class we will take pictures as part of Homework 2 (see

website) and experiment with the lenses Over the weekend - continue taking pictures as part of HW 2

Documents

Digital Photography Photo Organization September 13