Digital Camera Technical Guide
Overview
Resolution
Compression
Memory and Image Capacity
Power Source
LCD Viewfinders
Lens
Optical Zoom vs Digital Zoom
Focus and Exposure
Flash
Self-timer
Audio Recording
Movie Mode
Construction
TV Connections
Image Manipulation
Computer Connections
  Digital
cameras have revitalised photography as a hobby. Because digital cameras
record images on reusable memory cards instead of film, there are no
developing costs, so you can take as many pictures as you want and only
print the ones you like.
Overview
Most digital cameras feature an LCD viewfinder that lets you perfectly
compose your photo and then check any photos taken. Because the images
are stored as standard digital files, your computer becomes your
darkroom, letting you crop, enlarge and retouch your photos to
perfection. Some photo printers allow you to enhance your pictures too.
To share your photos, you have numerous options. You can e-mail them to
friends or post them on a photo-sharing website. If you want prints, you
can print them in the comfort of your own home on a photo printer. If
you don't have a PC, simply take your images to a photo lab and let them
process your prints for you.
Resolution
Resolution is one of the most important ratings of a digital camera.
Digital images are made up of dots called pixels. Resolution refers to
how many pixels make up a photo, and it is usually measured in the
horizontal by vertical resolution, as in "1,280 x 960", or as a total,
as in "1.2 megapixels" (meaning 1.2 million pixels). The higher the
resolution, the sharper the picture. Today's digital cameras generally
range in resolution from 4MP to 8MP although much higher resolutions are
available for professional use. Common digital camera resolutions
include 2,048 x 1,536 (3 megapixels), 2,240 x 1,680 (4 megapixels),
2,560 x 1,920 (5 megapixels), 3,032 x 2,008 (6 megapixels). To print
good photo quality prints up to A4 then a 4MP camera is recommended. For
anything larger, a 5MP or higher would be more suitable.
The resolution you need depends on what you plan to do with your
photos. If you just want to e-mail photos to your friends or put them on
the Web, you may be happy with a low resolution such as 640 x 480. If
you want to print your photos, however, plan on having at least 150 or
more pixels per printed inch. If you try to print lower-resolution
images at larger sizes, the results tend to look grainy, blurry or
blocky. Most cameras also offer the option of taking lower-resolution
photos so that you can fit more photos in the camera's memory.
Compression
Another factor that affects image quality is compression, the process
that shrinks a photo's file size. Most cameras take photos as compressed
JPEG files, which allows you to store more images on a memory card.
Compression also makes it faster to save and download photos and easier
to e-mail photos or download them as part of a website. For most uses
compressed images are adequate. Compression causes a small amount of
data loss, however; if you need the absolute best-quality images for
professional use, consider buying a camera that takes uncompressed
photos. You'll only be able to fit a few uncompressed images on a memory
card, but you'll get the sharpest, clearest, most-detailed pictures
possible.
Memory and Image
Capacity
Memory, the equivalent of film in a conventional camera, is where
pictures are stored as you take them. A camera's memory size will
determine how many images you can store, however, this generally won't
hold more than a handful of pictures taken with a high resolution.
Most consumer cameras use external memory, generally in the form of a
reusable memory card that you can remove when it is full. Common types
of memory card include
CompactFlash,
SmartMedia,
SD (Secure Digital),
Memory Stick and
xD. You can increase the number of photos you can take by buying
additional cards. To find out more about what type of memory you need to
buy read our
Memory Card Buying Guide.
Unlike film, the memory card can be reused once your pictures are
safely stored on your computer, making digital photography a very
cost-effective way of taking pictures. Larger capacity cards provide
storage for many hundreds (or even thousands) of photos at a time.
The actual number of pictures that can be stored on a memory card
varies from camera to camera and depends on a selection of factors
including compression settings, storage formats and image complexity.
Bearing this in mind, the table below attempts to indicate the
approximate quantity of images that can be fitted on to various sizes of
memory card, based on average file sizes and common compression ratios.
Power Source
Digital cameras use significantly more power than traditional cameras.
While typical cameras usually need their batteries replaced every 15
rolls of film or so, you might find your digital camera running out of
batteries before you've filled its memory, especially if you use the LCD
(Liquid Crystal Display, technology used to create low-power, slim
display panels) all the time. Digital cameras use either a rechargeable
battery pack or traditional batteries; some come with an AC adapter as
well. Consider buying an extra battery pack or investing in rechargeable
batteries and always have extras on hand. See our full range of
Batteries & Chargers.
LCD Viewfinders
Digital cameras come with an LCD screen built into the back. The LCD
screen is especially useful because you can see what your picture will
look like before you take it. It also allows you to look at the photos
you've already taken. Some cameras even let you display pictures on the
LCD screen in thumbnail format, usually nine or 12 to a screen. Most
cameras also let you select pictures to erase; this handy feature gives
you the chance to edit out the photos you don't want in order to free up
memory. As mentioned above, using the LCD screen is a significant
battery drain, so if you use it often, have extra batteries on hand.
You'll still find tradional viewfinders on some Digital Still Cameras as
well as the LCD.
Lens
The length of a camera's lens determines how much of a scene will fit in
a picture. Lens lengths vary between wide-angle (used for landscapes and
shots in which you want to include as much as possible) and telephoto
(used for close-ups and to zoom in on faraway objects). "Normal" lenses,
about 50 mm on traditional cameras, most closely approximate what your
eye sees; anything shorter than 50 mm is considered wide-angle, while
anything longer is usually considered telephoto.
The image sensor in digital cameras is smaller than the surface of a
35 mm negative, so lenses on digital cameras tend to be much shorter
than on traditional cameras. Look for the "35 mm equivalent" rating to
get a better idea of a camera's range. Most fixed-length lenses on
digital cameras fall somewhere between wide-angle and normal focal
length.
Optical Zoom vs
Digital Zoom
Most digital cameras come with some form of zoom facility. This allows
you to move from wide-angle (ideal for landscapes for example) to
telephoto (for close-ups). Clever use of zoom facilities can really
improve your pictures, allowing you to perfectly frame portraits or get
closer to the action when this might not be physically possible.
There are two types of zoom used on digital cameras--optical and
digital--both of which are rated by how many times "larger" they can
make a distant object. "3x optical, 5x digital" on a camera's
specifications, for example, means that a camera's optical zoom can
magnify by a factor of three, with the digital zoom providing a
magnification of five--in combination providing a maximum theoretical
magnification factor of fifteen times.
When using an optical zoom, the camera's lens does all the hard work,
increasing or decreasing the apparent size of your subject in your
picture in much the same way as a pair of binoculars. A digital zoom, on
the other hand, is nothing more than software in the camera that crops
the edges off of your image and blows up the remaining information to
the size of the original. This method has limitations however, with the
extra close-up power this provides coming at the expense of resolution.
This can be a particular problem on cameras with a relatively small
megapixel rating, as images can become slightly blocky and lacking in
detail. We recommend getting a camera with an optical zoom, using this
as your primary means of magnification and only resorting to the digital
zoom when you require extra magnification, as this will help keep your
pictures as crisp and sharp as possible.
Focus and Exposure
Fixed-focus digital cameras have a non-moving lens that is preset to
focus at a certain range. Higher-end digital cameras usually have
autofocus instead, which automatically focuses the camera at your
subject's distance.
Most cameras automatically determine the correct exposure for the
lighting conditions. Sometimes, however, the scene will appear too dark
or too washed-out. In these cases, it's handy to have a digital camera
that offers manual exposure compensation, allowing you to set the
exposure a few stops brighter or darker. A digital camera's
ISO-equivalent rating lets you know how light sensitive it is; a camera
rated ISO 100, for example, has about the same light sensitivity as a
traditional film camera loaded with ISO 100 film. Higher ISO ratings
mean the camera is more sensitive to light and can take pictures in
darker settings.
Digital cameras work just like traditional cameras when it comes to
aperture: the maximum aperture rating of a camera lets you know how much
light it can let in. Aperture ratings represent ratios; the lower the
aperture rating, the more light sensitive the camera is and the better
it can take photos in low light.
Flash
Most digital cameras come with a built-in flash. Basic flash modes
should include automatic (senses when to use the flash according to
lighting conditions), on (for all photos), and off. Some cameras include
additional features, such as red-eye reduction or night portrait mode.
Red-eye reduction is ideal for photographing people or animals--it fires
a series of short flashes before the final flash and exposure, making
your subjects' pupils contract and preventing them from having glowing
red eyes in the final photo. Night portrait mode sets your flash to go
off at the beginning or end of a long exposure, letting you take
portraits set against a night scene, such as a cityscape. However, you
should find something steady to set the camera on; the long exposure
needed for low light will turn any shake of the camera into a blurry
spot in your image.
Self-timer
A self-timer sets your digital camera for a delayed exposure, usually
giving you about 10 seconds before it takes the picture. This feature is
useful for getting yourself in the photo and can also be used to take
low-light photos, preventing the camera shake caused by pushing the
exposure button.
Audio Recording
A few digital cameras have the ability to record a few seconds of audio
with each shot, letting you add a personal sound bite to your photos.
This feature tends to eat up battery power rather quickly, so if you use
it often, be prepared with extra batteries.
Movie Mode
Many digital cameras now include movie mode, a feature that lets you
take short film clips with your camera. To keep from instantly filling
your memory card and overwhelming the camera's processor, the movie's
resolution is usually much lower than the camera's maximum resolution,
and the total length is typically limited to 10 to 90 seconds. It won't
replace your camcorder, but it's a fun additional feature. Some models
will record movies with sound, and some will only limit the length of
the recorded clip based on the size of memory card installed.
Construction
The first digital cameras were heavy, clunky boxes that could hardly be
called stylish. But today's digital cameras are sleek, stylish,
lightweight form of traditional point-and-shoots, and many feature
stainless-steel casings for added durability.
TV Connections
Some digital cameras include a video-out function that gives you the
option to hook them up to a TV to display your pictures. With this
feature, you can also record your pictures onto a VHS tape.
Image Manipulation
Most high-end cameras include software and connections for both Mac and
PC computers, but make sure the digital camera you want is compatible
with your platform before you buy it. All consumer digital cameras come
with the software you need to download your pictures onto a computer.
Also, most will include image-editing software--which lets you crop,
adjust, or add special effects to your photos. The software supplied is
not always the best you can get, so you may want to consider investing
in a separate
image-editing application.
Computer Connections
Digital cameras can use a variety of different interfaces. Most use a
USB interface, which plugs into a port on the back of your computer and
the required cables are normally included in a digital camera package.
Others come with a PCMCIA interface, which can be inserted directly into
a notebook computer. Another way to download images to your PC is via a
memory card reader.
Once you've downloaded and edited your images, most e-mail programs
will let you attach them to messages. You can also upload them to your
website or copy them onto a
CD-R to give to your friends and family. Some colour printers have
slots that accept a camera's memory card and let you directly print your
photos. Other printers come complete with dock, so there is no need for
cables, just simply dock your camera on the printer. Alternatively, you
can use the printer hooked up to your computer. One of the advantages of
using a digital camera is that you can make copies of your photos
whenever you want, without having to hunt through negatives and send
them out for processing at a lab. You can also make calendars, greeting
cards, collages, and enlargements easily and inexpensively at home. See
our selection of
photo printers.
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Related Products
Shop by resolution Whether you're looking for a
low-price starter model or a just-introduced, top-of-the-line
model, we've got a digital camera that fits your needs. As a
rough guide, the more megapixels, the better the quality and the
higher the price.
Under 3 megapixel
3 to 3.9 megapixel
4 to 4.9 megapixel
5 to 5.9 megapixel
6 to 6.9 megapixel
7 to 7.9 megapixel
8 plus megapixel
See all digital cameras
Visit the Canon shop
Visit the Fuji shop
Visit the Kodak shop
Visit the Nikon shop
Visit the Pentax shop
Visit the Sony shop
Extra memory can vastly expand your options. We've got
plenty of memory cards, including SmartMedia, CompactFlash,
Memory Stick and more. Browse our
memory card selection.
Protect and serve with our collection of essential
extras, including
batteries,
bags and cases,
cables and leads and
digital lens accessories.
Print your photos at home with a photo printer. Browse
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