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Digital

Imaging


Contents Capture

1

Convert

4

What is digital a image?

5

ISO Ratings

8

Bit Depth

9

Seeing Photography

11

Composition

13


Capture

D

igital photography gives

dramatically, and then you can

you tools to do just

print it out at your desk.

that; to enhance and

however, you can also send your

combine them in ways that were

picture by e-mail or display it on

formerly available only to those

an internet website.

with years of experience. To understand digital imaging,

1 Digital Imaging

Unlike traditional photography

manipulate your images and to

First, an image must be digitized, that is, converted to

compare it with conventional

a numerical form that is usable

photography. With digital

by the computer and that can

imaging, instead of exposing and

be displayed on the computer’s

developing film, you captured

monitor. The image that comes

an image by recording a scene

through the lens on your

with a digital still camera or

camera is in analogue form - a

video camera, or you digitize

continuously variable scale

an existing image by using a

of brightness and colour, like

scanner to read the image into

the volume on a stereo, which

a computer from a conventional

changes in smooth gradations

negative, slide, or print.

from soft to loud. Similarly, the

Instead of a darkroom you

image on a conventional slide

use image editing software such

or negative has a continuous

as Adobe Photoshop to change

scale of tones, with unbroken

the image, either subtly or

gradations from light to dark.


Convert

F

or computer use, the

The computer can reassemble

image is converted to

the grid from these numbers

digital form by using

and display it on a monitor or

CCDs (charge-coupled devices). A digital camera’s recording

send it to a printer. When the grid is very fine,

chip contains millions of light-

the pixels are very small –

sensitive CCD cells arranged

your eye perceives an image

in a grid, like squares on a

in continuous tones, just as it

sheet of graph paper. CMOS

would in a film–based photo.

(complementary metal-oxide

The finer the resolution is, the

semiconductor) technology

larger the number of pixels

performs the same function.

needed to complete the image.

A scanner that digitizes an

Whether you plan to

existing photograph uses a line

work on a photograph taken

of CCD cells that record one row

with a digital camera or one

at a time to assemble the same

scanned into digital form

kind of grid. Each position on

from a traditional print, slide

the grid is recorded on a pixel, a

or negative, you will want to

square with a uniform brightness

understand the relationship

and colour. Each value and its

between file size and resolution

position is saved and transmitted

(the fineness of detail) in your

as a series of numbers.

final image.

For digital imaging, an image is

pixels are too small to be seen,

recorded in a grid of pixels or

and the eye perceives the image

picture elements. Ordinarily, the

in continuous tones.

Digital Imaging

4


What is a digital image? site of coloured tiles

A

of a photograph, like the surface

need 16 tiles (four tiles by four)

that creates a realistic

where the mosaic is being

to fill the one-square-foot space.

scene in a mosaic. The more tiles

installed – a one-foot-square on

in the mosaic, the more detail

a bathroom wall, for example.

is possible in the scene. Each

Resolution is the number

digital image is like a

5 Digital Imaging

Image size is the physical size

be three-inches-square. You will

If you kept the space the same size but used smaller tiles – say one-inch-square – you

pixel in an image is one tile in

of pixels (or tiles) per unit of

could make a design with much

the mosaic; the image file size

length, in pixels per inch (or tiles

finer detail, but then you would

corresponds to the total number

per foot). If your resolution is

need 144 more tiles. Finer detail

of tiles.

four tiles per foot, the tiles must

demands a larger file.


For the same image size,

size) and how much details you

higher resolution looks finer

need (resolution) in order to

but requires more pixels. You

determine how many pixels (file

need to know how large you

size) will be required.

want your image to be (image Digital Imaging

6


ISO Ratings

A

digital camera often let

cameras adjust for the light

of view as a lens on a 35mm

you select the ISO rating

source automatically. With

camera, the lens focal length

for each shot. Using a

others you select the kind

on most digital cameras is

higher ISO can be an advantage

of light – daylight, tungsten,

somewhat shorter.

that lets you shoot in lower light,

fluorescent, cloudy or flash – so

but just as graininess becomes

colours are rendered normally.

Most manufacturers of digital cameras publish a

The lens focal length may

‘35mm equivalent’ focal that,

films, random specks called noise

give you an unexpected angle

if you are familiar with 35mm

occur more often in a digital

of view. Many cameras capture

cameras, helps you to know

image as you increase the ISO.

pictures on a CCD or CMOS

what will appear in the frame.

You do not need colour

more visible with high-speed

chip that is smaller than the

Keep in mind that shorter lenses

correcting filters when you

traditional 35mm film frame.

give you more depth of field

use a digital camera. Some

So to provide the same angle

regardless the frame size.

Digital Imaging

8


Bit Depth

C

omputers record

shades of grey in between.

of the same size, one with smaller

information in binary

The size of an image file is the

(and therefore more) pixels can

form using combinations

number of bytes that it contains.

hold finer pictorial detail.

of the digits one (1) and zero

The amount of information in

(0). A Bit is the smallest unit of

a digital image – and therefore its

divided the colours and tones

information, consisting of either a

technical quality – is determined

in each pixel (the bit depth

one or a zero, so it can represent

by both the number of pixels

or number of bits per pixel),

only two different possibilities

and the number of possible

each pixel can render a greater

– yes or no, black or white, on

values each pixel can hold. The

selection of possible colours and

or off. A byte is an eight-bit

greater the numbers of pixels

tones. Many other factors affect

sequence that can represent

that represent a given image, the

quality, but in general, the more

28 (or 256) possibilities, such as

greater the amount of detail that

data for an image, the better the

black, white, and 254 different

can be recorded. In two pictures

final photography will be.

Bit : Smallest unit of digital information Byte : 8 bits Kilobyte (K or KB) : 1,000 bytes Megabyte (MB) : 1,000,000 bytes Gigabyte (GB) : 1,000,000,000 bytes Terabyte (TB) : 1,000.000.000.000 bytes

9

Digital Imaging

Similarly, the more finely


1 bit per pixel gives two colours. The image can have only

two tones: usually black and white.

8 bits per pixel gives 256 tones. From 0 (black) to 255

(white), 256 tones provide excellent black-and-white rendition but are not enough for good colour.

24 bits per pixel gives 16,777,216 tones, enough for a

colour image with smooth gradations and full tonality, comparable to traditional colour film photography. Colour photography is made up of three images, one in each of the three primary colours. With 8 bits each, those three colours (red, blue, green) can each have 256 different shades – red from darkest to lightest for

example – making more than 16 million possible colours.

Digital Imaging 10


Seeing Photographs How do you learn to make better picture?

E

very time you make

speed to freeze motion sharply

an exposure you

or a slow shutter speed to blur

make choices, either

it? Your first step is to see your

deliberately or accidentally.

options, to see the potential

Do you show the whole

photographs in front of your

scene or just a detail? Do you

camera. Before you make an

make everything sharp from

exposure, try to visualise the

foreground to background or

way the scene will look as a

have only part of the scene in

print. Looking through the

focus? Do you use a fast shutter

viewfinder helps.

Framing the picture

T

11 Digital Imaging

he scene is then at least

a picture communicates its visual

reduced to a smaller size

content. Photography transforms

and confined within the

a three-dimensional event into a

edges of the picture doormat,

frozen instant, reduced in size on

just as it will be in the print. As

a flat piece of paper. The event is

you look through the viewfinder,

abstracted, and even if you were

imagine you are looking at

there and can remember how it

a print, but one that you can

“really� was, the image in front

still change. You can eliminate

of you is the tangible remaining

a distracting background by

object. This concentration on

making it out of focus by

the actual image will help you

changing your position to a better

visualise scenes as photographs

angle, and so on. Try to see how

when you are shooting.


O

ne of your first choices

clearly. In many cases, however,

for the intensity and immediacy

is how much of a scene

it was a particular aspect of the

of his images. This simple piece

to show. Whether the

John Capa The Battle Begins

subject that got the photographer’s

of advice can help most beginner

An American soldier landing on

subject is a person, a building,

attention in the first place, perhaps

photographers improve their

Omaha Beach, D-day, June 1944

or a tree, beginners often are

the expression on the face of the

work. Getting closer eliminates

reluctant to show anything less

person, the peeling paint on the

distracting objects and simplifies

than the whole thing. People often

building or a bent branch of the

the contents of a picture. It

photograph a subject in its entirety

tree. Get closer to subject. “If your

reduces the confusion of busy

– Grandpa is shown from head to

pictures aren’t good enough, you

backgrounds, focuses attention on

toe, even if that makes his head so

aren’t close enough,’” said Robert

the main subject, and lets you see

small that you can’t see his face

Capa, a war photographer known

expressions on people’s faces. Digital Imaging 12


Composition What is your photography about?

I

nstead of shooting right away,

setting reveals something about

stop a moment to decide which

the person.

part of a scene you really want

to show. You might want to take

the photograph to look like.

one picture of the whole scene,

Then move around as you look

then try a few details.

through the viewfinder. Examine

Sometimes you won’t want to

13

Digital Imaging

Try to visualise what you want

the edges of the image frame.

move closer, as in photographing

Do they enclose or cut into the

a prairie landscape where the

subject the way you want? In

spacious expanse of land and

time these decisions come more

sky is important or in making an

intuitively, but it is useful at first

environmental portrait where the

to work through them deliberately.


Arthur Siegel Right of Assembly 1939 Siegel shot from a high vantage point to get in as much of this street demonstration as possible. He wanted to show each demonstrator as an individual expressing a common belief, so he filled the frame with them and tried to get them all in sharp focus.

Digital Imaging 14


Jerome Liebling Cop’s Hat Union Square New York 1948

A

detail of a scene can

very shallow depth of field. In the

tell as much as and

entire shot only the policeman’s

sometimes more than

hat is in focus and the eye is drawn

an overall shot. Liebling shot

to it instantly. A very small part of

from below eye level, a humble

an image, like the badge, can carry

vantage point, and intentionally

considerable symbolic weight.

used a very wide aperture to get

15

Digital Imaging


Lee Friedlander Route 9W New York 1959

C

ombining different

mind finger presses the release

elements in a scene

on the silly machine and it stops

can bring order out of

time and holds what its jaws can

chaos or sometimes a sense

encompass the light will stain.

of dislocation to ordinary. Lee

That moment when landscape

Friedlander wrote, “The camera is

speaks to the observer.”

not merely a reflecting pool…The

Digital Imaging 16



Digital Imaging