Frequently Asked Questions on Digital Photography (Digital Library Vol. 4)

77 Pages·2002·1.561 MB·English

Digital Library
Volume 4
A
F
Q
FREQUENTLY
ASKED QUESTIONS
on
DIGITAL PHOTOGRAPHY
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Frequently
Asked Questions
on
Digital Photography
Digital Library Vol. 4
Disclaimer: While every endeavour has been
made to provide accurate information, no
liability will be assumed for typographical
errors and omissions or technical inaccuracies.
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Contents
1. The fascinating world of digital photography 4 3.13 Blackboard/Whiteboard 46
3.14 Movie mode 46
2. Digital camera technology 8
3.15 Sound recording 47
2.1 How does a digital camera work? 8 3.16 General tips and hints for better photos 47
2.2 The CCD chip 9
2.3 What to look for when buying a digital camera 13 4. Printing digital images 50
2.4 Factors affecting image quality 16 4.1 Traditional photos vs. digital photo prints 50
2.5 The importance of a good lens system 18 4.2 Home printing 51
2.6 Long-term storage of digital images 20 4.3 Printing services for digital photos 56
2.7 Servicing digital cameras 21 4.4 Enlarging digital prints 57
2.8 Power sources 22
5. Archiving digital photos 60
3. Taking digital pictures 24 5.1 Software solutions 60
3.1 Metering systems 24 5.2 Recommended hardware 62
3.1.1 Exposure metering systems 24 5.3 Downloading images from memory cards 63
3.1.2 Focus systems 27 5.4 Connecting a digital camera to a computer system 64
3.1.3 White balance 28 5.5 Important image file formats 65
3.1.4 Sensitivity 31 5.6 Copying images to a CD-ROM 68
3.2 The camera flash 32
6. Compressing image data 70
3.3 Image optimisation systems 34
3.3.1 TruePic 34 6.1 Storage requirements 70
3.3.2 Noise reduction 35 6.2 The important compression methods 71
3.3.3 Pixel mapping 36 6.3 Selecting the right compression level 74
3.4 Scene programs 36 6.4 PKZIP/WinZIP and StuffIt 75
3.5 Manual control 37 6.5 Pixel number in compression 76
3.5.1 Aperture 37 6.6 Saving images in different file formats 76
3.5.2 Shutter 38
7. Editing digital images 78
3.6 Histogram 39
3.7 Zoom 39 7.1 Image editing programs 78
3.8 Macro shooting 40 7.2 Sending image files by email 79
3.9 Sequence shooting 42 7.3 Transferring digital data with a mobile phone 80
3.10 Self-timer 43 7.4 Digital images for the internet 81
3.11 Panorama 43 7.5 Viewing digital pictures with the TV 83
3.12 B & W and sepia 45 8. The A to Z of digital photography 84
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1.The fascinating world
of digital photography
“A picture says more than a thousand words.”
This is certainly one explanation for why photo-
graphy has lost none of its power to fascinate
and enthral in its almost 200 year history.
Even though the cameras were still expensive,
heavy, cumbersome and complicated well into
the 20th century, these failings proved to have
little influence on the technology’s success.
The reason: for the first time it was possible to
capture moments in time and illustrate feelings,
moods, desires at more or less the press of a
button. Photography was here to stay.
Whether digital or analogue, in the studio or
out in the open, photography is always much
more than just capturing reality. It is also the
interpretation of what the photographer sees
and the transformation of this into a new, two-
dimensional reality so that the moment comes
back to life when the image is viewed.
It’s a pity then, that with conventional analogue
photography the results cannot be seen immedi-
ately, checked or edited until the film has been
exposed and developed.
While the instant photo technology introduced
by Polaroid went some way to changing this, it lower cost of components (LC-Displays, CCD
was digital imaging that really revolutionised the chips, etc.), led to the first affordable, digital
photographic experience. cameras appearing on the consumer market in
the mid 90s.
Initially, this new technology was prohibitively
expensive and really only attractive to technologi- Similar to the development of the computer,
cally adventurous pro users. However, as a result digital photography has experienced a dramatic
of the internet and email boom, demand for easy- increase in performance power. For example,
to-produce and affordable digital images rose whereas the first consumer camera had a resolu-
to unforeseen levels. This, together with the ever tion of only around 300,000 pixels, today there
are models with five million pixels or more that
not only meet the needs of professional photogra-
phers but also fit the price range of amateurs.
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1.The fascinating world
of digital photography
The growth in the number of manually adjustable So, it’s hardly surprising that the digital camera
shooting parameters is equally impressive. While market has been enjoying such an extraordinary
the earliest models featured as good as no growth rate. While the total of digital cameras
individually adjustable settings, modern digital sold in 1996 reached just about 1.2 million (of
cameras are on a par with their analogue counter- which only 100,000 were sold in Europe), this
parts when it comes to manual control. number had risen to 18.5 million worldwide in
2001.
The reasons for the appeal of this imaging tech-
nology are manifold. These are just ten examples: However, since a large proportion of digital
camera users are new to the technology (and
1. No need to buy film ever again. not always familiar with the workings of PCs),
and because of the rapid development in this
2. Storage media is reusable. field, new questions constantly arise and older
ones go unanswered. In this booklet we have
3. Images can be checked and enjoyed therefore tried to present short, to-the-point
immediately after capture. answers to frequently asked questions. Naturally,
this brochure will not be able to cover all
4. The cameras’ optical systems are of the aspects of this complex subject. We would
highest quality and have a superior lens though be delighted if the FAQ could help you
resolution compared to those in analogue get more enjoyment from digital photography
models. and even obtain better results.
5. Silent operation for discrete shooting.
6. Creative effects possible even at the
recording stage.
7. Presentation of the images on a TV
(slide show).
8. No loss of quality when copying and
transferring data.
9. Editing images later is easy.
10. Prints can be produced and photos sent via
email immediately.
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2.Digital camera technology
2.1 How does a digital camera work? The heart of the digital camera is hidden behind
the aperture. The CCD (Charge-Coupled Device)
Digital cameras cannot be so readily compared chip is a light-sensitive semiconductor element
to analogue cameras, which use slide or negative made up of many silicon diodes. When light hits
film. Seen from a technological point of view, the individual photosensitive diode, it causes it to
they are more similar to video cameras that take generate an electrical impulse which is read by
one image at a time. the camera.
First, let’s look at how an The →analogue-digital conversion process converts
analogue camera works. the analogue impulses for each image dot into
The analogue digital values for brightness. Those digital values
camera Simply put, it consists of a are then calculated by the camera's imaging pro-
lens system,an cessing engine, comprising an →ASIC chip and
apertureand a software, to make better images (for example, by
shutter.The lens optimising gamma conversion and colour repro-
system ensures duction). The reconstructed digital image is then
the captured transferred into the camera's storage media.
image is in focus
while the →aperture and
→shutter control the amount of light reaching the
2.2 What is a CCD chip?
film. As soon as the shutter is released, light is let
into the camera through the →lens system and
aperture to land on the photosensitive film. The
resulting chemical reaction records the image on
the film surface. This image is then set in the
developing process.
→Pixel:
Although digital cameras Abbreviation for
may often look like their “picture element”.
The digital analogue counterparts and It is the smallest
camera element of a
share many components,
raster display or
such as aperture, shut- digital picture,
ter and a lens system, containing infor-
their methods for mation about
brightness and
recording images differ colour. Generally, The CCD chip is about as large as your fingernail
radically. Instead of in a monitor or and has millions of photosensitive diodes
light-sensitive film, they ink-jet printer, a arranged in columns and rows on its surface,
use a combination of →CCD chip, →imaging pixel can consist much like the dots, or pixels, on a computer
of up to 256 dots
processing engine and storage media to capture per colour. monitor.
the image. Exception:→Dye
Sublimation.
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2.Digital camera technology
If each of the sensors on a CCD
chip were to react to incoming Even and odd rows
are read separately
light in the same way, a digital Video CCD
camera could only take black
and white pictures. However, to
ensure that all colours can be
captured, the sensors are covered
with different colour filters – either RGB (Red,
Green, Blue) or CMY (Cyan, Magenta, Yellow)
with additional green filters for more true-to-life
results.
Besides colour, brightness data is also required 1, 3, 5 etc. To allow uninterrupted reading, the
for correct image reproduction. The light for each digital camera uses a mechanical shutter to
of the three colours is divided up into 256 levels prevent more light entering the camera.
of intensity. This combination of 256 x 256 x 256 Due to their high performance, relatively simple
yields 16.7 million possible colours for true construction and low production costs, video
colour reproduction. CCDs are found in many digital cameras.
The captured data is transformed into digital sig- Another type of CCD called the progressive scan
nals so that all relevant image information can be CCD, or simply progressive CCD, can record a
stored by the digital camera. number of complete images per second. Because
the image is captured and read in one movement,
Basically, there are two different kinds of that is row after row (1, 2, 3, 4 etc.), a mechani-
CCD chips which can be used in digital cal shutter is superfluous and exposure time can
cameras. The first was originally devel- be controlled electronically, enabling extremely
oped for television and video and has high shutter speeds. Consequently, cameras with
since been optimised for still cameras. progressive CCDs are ideal for sports and action
Called the video, or interlaced CCD, it photography.
has the advantage of high light sensitiv-
ity and features either RGB or CMY and green
colour filters.
Progressive CCD
Although this CCD captures the information in
one shot, the data is read in two sequences: Data read
first, rows 2, 4, 6 etc. of the CCD, and then rows in
one pass.
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2.Digital camera technology
A progressive CCD is coated with 2.3 What should I take into account when shopping
RGB (Red, Green, Blue) colour fil- for a digital camera?
ters. Since each pixel in the picture
corresponds to one of the three types Before buying a
of CCD pixels, only one colour is digital camera you
recorded for each dot. An imaging should think about
processing engine is used to calculate and what you intend
complete the missing colour data. The better to use it for. If you
the imaging processing engine program, the are looking for a
better the resulting picture will be. model for taking
snap shots at
An additional improvement in picture quality is family gatherings
achieved by a relatively simple trick. By modify- or on holiday, for
ing the CCD chip’s proportion of green-filtered example, you would be best served by a fully-
pixels to contain two green filters for every red automatic compact or compact zoom camera
and blue filter, the subject can be reproduced that takes care of all the details.
even more precisely.
For users who want the convenience allowed by
The reason for this: not only is the human eye a compact, easy-to-use model but also wish to be
more sensitive to green but the colour green also able to add their own personal touches from time
significantly influences our perception of bright- to time, there are a number of competitively-
ness. priced user-friendly cameras that offer a range of
adjustable settings, such as shutter speed, aper-
An alternative to the CCD chip is the CMOS ture and white balance, as well as picture effects
chip, which also employs light-sensitive diodes like →sepia recording.
for capturing images. While these chips have
certain advantages over the CCD, not least in To meet the quality and performance
being relatively cheap to produce and having requirements of the professional photog-
comparatively low energy requirements, many rapher, the camera needs to combine
manufacturers still prefer to use CCDs in their a very high →resolution and precision
cameras because the CMOS chips usually pro- lens with extensive shooting control.
duce far too much noise, significantly affecting It also should allow the connection of
image quality. accessories, such as converter lenses
and external flash systems, including,
via an →x-contact, studio flashes.
A variety of models, mainly digital
SLR’s, meet these criteria.
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2.Digital camera technology
So, what features should you look for in a digital sufficient. Where it is too difficult –
camera? Digital photography is all too often or too dangerous – to get close to the
described as digital technology plus some photo subject, such as when taking pictures
technology. However, it is actually photo technol- of the action at large sporting events
ogy that uses digital technology. Therefore high or of animals in the wild, an 8x or
resolution lenses, efficient flash systems, and, 10x lens is very helpful. Many models
if desired manually adjustable parameters are also feature digital zooms. While
important in a digital camera. these provide additional magnification
power, they are accompanied by a
→Zoom lenses let you get closer to the subject. reduction in resolution which in turn
Generally, the larger, more powerful the zoom means a decrease in image quality.
lens, the more expensive and heavier the camera
(though digital camera zoom lenses are far more Fast shutter speeds of 1/1000 sec.
compact and lighter that those on analogue and over are also desirable when
models.) For everyday use, a 3x lens is usually taking pictures of fast moving sub-
Zoom versatility jects, such as birds or cars. On the
other hand, you should look for a
camera that offers very slow exposure times if
you intend to take pictures in low light or at
night, for example.
Besides comparing general shooting features, you
should also examine the digital camera’s image
storage capacity. Since each recorded picture (in
spite of image →compression) requires relatively
large amounts of memory, you should make sure
that the camera in question comes equipped with
quickly replaceable memory cards or storage
modules. These allow you to change the media
within seconds so you can continue shooting.
Furthermore, it is best to check that the cards
are small, manageable, affordable, and provide
sufficient storage capacity.
As a rule of thumb, if you ensure that the digital
camera you want to buy has all the features you
would look for in a traditional (analogue) camera,
you can hardly go wrong.
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2.Digital camera technology
Undeniably, price is also a strong factor when pixel errors. Yet, if the CCD has been poorly
choosing a camera but this should not be the manufactured and contains too many pixel errors,
only criterion. With photography it’s the result there can be a noticeable effect on picture quality.
that counts and therefore you should consider the
picture quality of the camera before you decide That’s why a critical compari-
to buy. son of different models is the
only way to ensure you get the
best product. Pay special atten-
2.4 What factors affect picture quality?
tion to the sharpness of the
Four factors play a primary role in establishing image outlines and the acute-
the quality of a digital camera: first, the resolution ness of the pixels. If these
of the CCD; second, the way the CCD works; results appear to be satisfac-
third, the "intelligence" of the camera’s imaging tory, then check the reaction of
processing engine; and finally the optical con- the camera to different lighting
stituents of the camera. situations. Asking for a printout
of a digital photograph is also
The camera’s resolution, which is usually written recommended. By this point,
on its body and given in →megapixels, acts as an you will be able to tell how
initial, basic quality guide. Two megapixels are good the CCD chips really are.
sufficient for postcard sized prints (see also sec-
tion 4) and generally, the higher the resolution, Another factor that significantly
the better the camera’s pictures compared to determines the quality of pic-
those from lower resolution models. tures is the camera’s imaging
processing engine. Comprising
However, if you have a quick look at the prod- an ASIC chip and software,
ucts on sale or read the reviews in specialist this is responsible, among other things, for image
magazines you will soon discover that there are enhancement (such as →interpolation, gamma
quite large differences between cameras that conversion and colour reproduction.) Using spe-
offer the same resolution, especially when the cial computational processes, the processing
photos are printed. Why is this? engine adds information to the partially recorded
image data and separates the important from the
There are various reasons. One explanation is the unimportant image data. The more effective the
difference in methods used by CCD chips (see camera’s ASIC chip and software are in carrying
section 2.2) and the quality of their production. out these tasks, the faster it can be done and the
With millions of pixels compacted on a miniature better the quality of the final picture. For more
surface, it is hardly surprising that the majority of about this, turn to section 3.3.1(TruePic). In
all CCDs produced can have a number of more addition to the resolution and quality of the CCD
or less insignificant faulty pixels. Pixel mapping chip and the camera’s software, the optical tech-
(see section 3.3.2) helps compensate for some nology of the lens system also plays a key role in
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