Resolution, Memory Size, Memory Cards, Compression, Power Source, and more
Resolution
Maximum resolution is one of the most important ratings of a digital camera.
Digital images are made up of dots called pixels. The resolution of a digital
camera refers to the sharpness of its pictures and is measured by how many
pixels make up a photo, usually measured in the horizontal by vertical
resolution. (i.e. 1280 x 960 Pixels = film resolution of 4" x 6"
print). The higher the resolution, the sharper the picture. At the same time it
will also mean the more memory that will be required to store an image, both in
the camera and on your computer.
Memory Size
A camera's memory size will determine how many images you can store. If you
anticipate downloading your images often, buying a camera with a large amount of
memory isn't as important. However, if you plan to take multiple pictures before
downloading them to your computer you may want to buy a camera with a lot of
included or expandable memory or plan to buy an extra memory card.
Memory Cards
Some digital cameras have a non-removable memory chip embedded within the camera
for storing images. However, most consumer cameras use an external memory card
or even a floppy disk than can be removed when full. Most digital cameras ship
with enough memory to take from 12 to 36 shots at full resolution--about the
same as one roll of film for a traditional camera. To increase this capacity or
number of photos, you can buy additional external memory cards.
Compression
This is 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, or compressing images also makes it faster to save, download,
email and when compressed photos are used on a Web site it decreases the amount
of time it takes for a browser to load a Web page for viewing.
For printing out photos for albums, emailing or posting images on a Web site,
compressed images are adequate. However, compression does cause a small amount
of data loss, so if you need the absolute best-quality images, consider buying a
camera that takes uncompressed photos. You will only be able to store a few
images on a memory card, but you'll get the sharpest, clearest, most-detailed
pictures possible.
Power Source
Digital cameras use significantly more power than traditional cameras. A typical
film camera will usually shoot 15 or so rolls of film before the batteries need
to be changed, However, a digital camera may run out of batteries before it's
memory is filled, especially if you use the LCD all the time. To avoid this
problem consider buying an extra pack of re-chargeable batteries to have on
hand, select a camera that comes with an A/C adapter, and/or buy a battery
recharger.
LCD View-finders
Most digital cameras come with at least an optical view-finder like the ones on
a regular film camera but many digital cameras also come with an LCD screen
built into the back, which you can use as a view finder as well. With the LCD
screen 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. As mentioned above, using
the LCD screen requires a lot of power, so if you use it often, have extra
batteries on hand.
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 auto focus instead, which
automatically focuses the camera at your subject's distance.
Lighting
Most cameras automatically determine the correct exposure for the lighting
conditions, however there are cameras available that offer manual exposure
compensation. This allows you to set the exposure a few stops brighter or
darker.
Aperture Rating
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.
Red-Eye Reduction
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 works by firing 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.
Rapid-Fire Shots
If you plan on taking pictures of subjects in motion, such as during a sporting
event you may want to buy a camera that offers "Rapid-Fire Shots."
This feature allows you to take multiple pictures with one touch of the exposure
button.