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Some
aspects related to digital cameras are covered elsewhere
regarding general considerations about resolution and
DPI etc. However, many people are puzzled by references
to a camera's ''Mega Pixel'' specification.
Here we look briefly at this and a few other relevant
camera matters. Actual picture
taking is dealt with on another page. |
Digital
Camera ''Megapixels'' etc-
To figure out what size prints you can make from today's
digital cameras, you have to first break down the pixel
measurements.
For example, a 3.34 megapixel camera works out to give
dimensions of approximately 1536 x 2048 pixels, while
a 2.24 megapixel camera works out to give approximately
1280 x 1600 pixels. Note however ....... the quoted
pixel dimensions you may have specified by the maker,
when multiplied, will not usually quite total the megapixel
figure - this is because a small number of sensor positions
on the CCD (charge coupled device) are needed for registering
factors such as brilliance etc.
For a reasonable quality prints, 72 DPI will ''do'',
as long as image not being resized much, 150 pixels
per inch of resolution is more versatile and recommended
for web use where resizing often needed. For professional
quality prints you may usefully employ double that,
if a quality printer is also available. For simplicity's
sake, pick either the long or short dimension of the
print/camera resolution and work with that one. Note
here, the lack of need for especially
high resolutions when printing on domestic quality
printers.
For these examples to follow, we'll use the long edge
of the print. Let's work through a couple : -
Maximum print size (medium quality) for a 2.24 megapixel
camera --1600 (the long image dimension with 2.24 megapixels)
divided by 150 (pixels/DPI) = 10.7." Using this example,
you could get a medium quality print of up to about
10 inches (so you could get a medium quality 8"x10")
Maximum ''pro'' quality print size would be 1600 divided
by 300 = 5.3". In this case, you'd be able to get a
pro quality print at 3.5" x 5". Maximum print size (medium
quality) for a 3.34 megapixel camera -- 2048 (the long
image dimension with 3.34 megapixels) divided by 150
= 13.65", so you'd be able to get a medium quality print
of close to 11" x 14". Maximum pro quality print size
would be 2048 divided by 300 = 6.8." In this case, you'd
be able to get a pro quality print at 5" x 7."
Keep in mind ........ these guidelines are not absolute!
Your lens, lighting, CCD quality and method of printing
all play a huge part in the final results. Also, the
resolutions quoted are based on optical resolution and
not interpolated (upsampled) resolution. The formulas
can be applied to cameras of any resolution, or you
can work the formula backwards to find out how many
megapixels are required to get the image quality you
require at the size you will be printing.
There are many cameras available now - even 5 Mpix are
within reach. For most though a 3Mpix will get the job
done, particularly if 150 DPI or better.
Remember too -- if your images are only required for
web use, then you can keep sizes well down anyway...
meaning shooting with a 6 Mpix camera is really not
necessary.
To help with choosing a new digital camera ... go to
THIS PAGE
for some links and further suggestions ... opens in
a new window. |
Brief
function synopsis -
Initially, your image is passed through a lens,
like most cameras and that image is then eventually
focused on a reading device. Control of light passed
is by a form of shutter ..... that opens enough
to pass the required light level after a sensor
has ''read'' the scene.
Your digital camera has some similarities to a scanner,
in part ... particularly in as much as, the image
is passed through primary color filters to break
it up into the three main components ......Red,
Green and Blue. These are then ''projected''
onto a CCD (charge coupled device) usually, where
levels of intensity in each color component are
read as a voltage level. The analogue signal from
the CCD is then converted to digital via an A to
D converter and stored within the memory after processing
by an on board processor chip.
That processing will often include the imposition
of various algorithms to enhance, sometimes simplify,
and also compress the image down in size - usually
to a JPG format.
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General digital
camera matters -
Types of memory card -
Many cameras available nowadays, particularly
the less expensive, make use of their own type
of memory card. Now these work fine but, it is
well worth while considering a camera which uses
a standard ''compact flash'' memory card. The
reason is, these are the same as used with many
laptop computers, where they plug in to a small
socket called the ''PCMCIA'' interface. They then
behave like a small removeable hard drive. They
are often now the cheapest too.
A company called ''Sandisk'' markets a very inexpensive
device which will operate via your PC's USB port,
called an ''Image Mate'' ..... somewhere around
$25. The advantage then is that when you have
shot a load of pic's, you plug in the flash card
and upload your files in a couple of seconds .........
as against many minutes using a serial interface.
In more recent times however - further improvements
in market availablity now see multi card readers
available for simple USB use - and these will
handle about any memory card out there! One of
these will probably only cost around $30.
Zoom options
-
Choose your camera carefully if you want a zoom
facility. The only ''real'' zoom is optical, which
means the lens is capable of changes in focal
length ........ typically (in 35mm camera terms)
about 35mm to 70mm (2:1), or on more expensive
versions maybe 35mm to over 100mm (3:1).Many
cameras offering zoom in fact only give ''digital''
zoom. All this does is take a portion of the normal
(let's say - wide angle view) ....... and cut
out a piece. This is no different to taking a
whole image and cropping out a ''chunk'' in your
computer image software later. So, smaller picture
but resolution no better. It will not usually
look very good unless the original was taken at
a high resolution.
Power
Source -
When a camera has it's LCD screen in use, the
current drain on batteries is very significant.
Most will quickly go into a ''sleep'' mode if
not used for a while but, there is little more
frustrating than losing power at a critical moment!!
Furthermore, use of flash will also hasten the
discharging of batteries. Choose a camera which
allows use of removeable ''AA'' size cells.
As an absolute minimum, you should use high capacity
alkaline cells but these are generally ''throw
away'' and are expensive. Your next choice is
to use rechargeables. NiCd (Nickel Cadmium) types
are common (typically, ''AA'' size NiCd's have
a capacity rating of around 600mA to 700mA) but
nowadays it is best to invest in NiMHi (nickel
metal hydride).
These latter have a capacity often over twice
that of a NiCd and also do not suffer the ''memory''
effect either....... which means you can top them
up more safely, and not have to worry about deep
cycling them to maintain full capacity.
Cameras which seem to only offer the use of Lithium
replaceable batteries are not I feel very worthwhile.
Replacent batteries are expensive even if quite
good for duration.
What should I buy? -
I cannot and would not recommend specifics ....
only suggest you give consideration to some of
the suggestions above. I will just remind you
though that for the most part - you get what you
pay for. Very broadly, I consider that to get
something sufficiently useful and with adequate
quality, your budget should go no lower than $150.
Better if possible to aim at the $250 to $300
region, and above. Just my thinking.
Just a reminder - if you have not already visited
THIS
PAGE take a look at some more camera choice
factors and some links which might help also. |
So
- a very skinny look at digital cameras. A
look around on the web will give a whole heap
of information but hopefully the above will
give you a kick start if new to the subject.
If looking to buy, then a trip to dealtime.com
could well put you in the right places for
good deals on prices, but do pay attention
to specifications and buy carefully. Makes
like Cannon, Fuji, Nikon,Kodak etc are all
well worth some extra expense. Cheap can often
be money wasted.
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