When one is immersed in a subject, the way we are here at megapixel.net,
it is easy to lose sight of the fact that the technology, and its jargon,
can be a bit intimidating to someone approaching the subject for the first
time. This little guide is an attempt at at some demystification, and will
endeavour to show a path to a better understanding of digital photography,
using some of the resources available here, and in other valuable sites,
on the Internet.
Until very recently, a basic amount of computer literacy was needed to
seriously consider a digital camera as a replacement for a film one. This
is changing fast. Many stores that used to only offer film developing and
printing, are now offering their customers the possibility of bringing
in their digital images for printing, much like they had done with their
rolls of film. The difference is that these images are not recorded on
film, but as digital information stored in one type of "memory" or
another. And, that once the images have been copied, the customer gets
the "digital film" back, to reuse, again and again.
This development has opened the door of digital photography to a much wider
audience. No longer is it an absolute requirement to have, and know how
to use a computer. Many are realizing that digital photos do not suffer
from film's shortcomings: fading colours, loss of the negatives, etc. This,
combined with lower digital camera prices, has increased the attraction
of digital photography.
A look at the basics:
Digital cameras may almost appear magical, but they're not. The technology
employed to capture an image without the use of film is not really new,
only recently more affordable. Instead of film, the image is formed by
the camera's lens onto an image sensor, broadly similar to those used in
video cameras. The light is gathered by tiny elements on the sensor which
are referred to as "pixels". Each of these tiny sensors detects
the amount of light falling on them, as it is filtered by an overlaid colour
mask. In this way, the light gathered at the location of any given pixel
can be attributed to either red, green or blue, the basic colour components
of the photo.
This colour information is then "processed" by the electronics
in the camera so that the colour values gathered from all the locations
on the sensor are organized precisely, creating a "map" indicating
clearly the physical location of all the colours and their intensity. The
result is a digital image.
This electronic information is then recorded, in a digital file, each bit
of information processed by the camera being encoded as a "1" or "0" value,
sequentially, which can later be read by another digital device, such as
a computer, or a printer.
It is this digitization process which offers the true value of digital
photography. Indeed, once the image is in this digital format, it is nearly
indestructible, and can be copied time and time again without ever losing
its integrity.
The differences between a film camera and a digital camera
The differences between film and digital cameras can be placed into two
categories: the camera, and the system it uses to store the images. Let's
start with the camera.
The camera:
Unlike a film camera, the digital camera is not only the tool to focus
the image, but also the device that records it. In a way, a digital camera
is both camera and film. In a sense, when a digital camera is selected,
so is the film: the sensor that records the image.
Since the image is captured by the pixels of the sensor, the quantity of
pixels will determine the overall quality of the image. In general this
value is referred to as the resolution and is commonly expressed as the
total number of pixels (1, 2, 3 megapixel, "mega" meaning million);
or the number of pixels used to make up the image, stated as horizontal
and vertical values, as in: 2048 x 1536 pixels.
A corollary to the resolution of the sensor is that it also places a limit
on the size of the images at the time of printing, be it when the image
is printed in a store, or printed on a personal colour printer. Indeed,
to create a smooth image, one that can be compared to a print made from
film, a certain density of pixels per square inch is required, and this
minimum density, in turn, dictates the dimensions of the print.
Image storage:
As mentioned above, the other important thing to consider with a digital
camera is the way its images are stored. The digital images are generally
stored using a type of flash memory, which is a memory that does not require
a constant source of power to retain the information stored in it. Recently,
another way to store digital images was introduced, the CD. However, unlike
the flash memory used generally, the images are recorded once, and the
disks cannot (so far) be reused.
Leaving the CD-ROM type of storage aside, the flash memory designed for
digital cameras (known as memory cards) come in different flavours,
each more or less popular, and each offering varying price and capacity
advantages and disadvantages. The two most wide spread formats currently
are: CompactFlash and SmartMedia. To date, CompactFlash memory cards can
be purchased in larger capacities than can SmartMedia cards, but they are
generally more expensive.
Next month, we will delve a bit more deeply into the kinds
of digital cameras available, their current price range, and the
features they offer.
