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On traditional film the image is formed by silver chloride salts.
To simplify we can say that, once the film has been exposed to light, therefore once the
picture has been taken, they aggregate and the smaller and more dense they are, the more
the image will be detailed.
In place of the film, digital cameras have an electronic sensor named CCD (or CMOS) formed
by other very small elements, sensitive to the light, called pixels. Exactly the pixels
are directly responsible for the formation of the image.
Obviously the more they are, the better it will be. If they are a lot and dense the
electronic 'film' will be able to reproduce images with fine details, instead if they are
relatively few then the image will appear rather fragmented and dimmed.
It follows therefore that the quality of the image that 'digital-electronic' cameras
supply is directly proportional to the number of pixels that compose the CCD and it is
just based on the number of such elements that you can understand how good a camera is.
Fundamentally 4 categories of digital camera exist nowadays:
- for people who do not have any quality requirement (up to two million pixels),
- for less expert unskilled photographers (from two to four million pixels),
- for the more expert nonprofessional photographers (from 4 to 8 million pixels),
- for professionals and nonprofessionals who need high quality (beyond 8 million pixels).
With a series of other electronic characteristics, like the number of bit, the number of
pixels constitutes therefore the main factor in order to establish the value of a digital
camera.
We would ask on a theoretic line: how many pixels do we need in a CCD sensor to allow a
digital camera to take an image with the same quality of a 35mm. film? Therefore we can
reason this way: 24x36 millimeters = 2400x3600 pixels = 8,64 million pixels, a
considerable figure!
But this reasoning is only of theoretical value.
For its pro digital srl reflex Canon declares to have caught up with the same quality of
the photographic film with a sensor of beyond 11 million pixels and some other new cameras
have more. Unfortunately these cameras are not accessible to all pockets!
But you would be wrong if you think the number of megapixels (=millions of pixels) of the
CCD sensor is the only element to consider in purchasing a digital camera. There are in
fact other factors that, although they do not cover the same merit for all categories of
photographic customers, have however a particular importance in determining the yield and
finally the quality of the camera.
For instance the quality of lenses influences the final image more than may be thought. An
optimal objective (like those of the great tradition Houses like Nikon, Pentax, Canon,
Minolta, Sony-Zeiss etc) influences a lot the final yield of the image.
Other elements to be thought about are the 'power' of the zoom and, for a better
operativity, the possibility of manual controls, a larger display which easily visualizes
the shot, the presence of an optical view-finder and also that the camera is equipped with
some electronic system aimed at correcting the final images (e.g. like the Nikon Coolpix
series).
 Table:
How many megapixels?
Memories for digital cameras |
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