Nikon Digital cameras can allow the quality and resolution
of a picture to be selected before it is taken.
Resolution
Resolution is the number of pixels (see "What is a Pixel?) from
which the image is composed. A digital image is made up of tiny squares of colour called
pixels. The more pixels and image has, the finer the level of detail that is captured in
the image. When it comes to viewing or printing the image, a typical computer display
normally operates at about 72 pixels per inch, whereas for (ink-jet) printing a resolution
of about 180 is required. Therefore to display a post-card size image on a screen the
image should be about 450 x 300 pixels, and to print the same size image, it should have a
resolution of about 1000 x 600 pixels.
You can choose the image resolution knowing the intended output when you take the
photograph, or if you are unsure whether you will need to print the image or view it on a
screen, chose a resolution which gives you enough pixels for both.
Tip: When viewing an image in Internet Explorer the program will display all images at
the same number of pixels per inch/cm. Therefore a high resolution image will simply look
bigger, rather than more detailed. It is only when two images of different resolution are
viewed or printed at the same physical size that the difference in detail becomes
apparent.
Quality
Nikon digital cameras use a technique called compression to reduce the
amount of space taken up by an image on your CF card or computer hard disk, and therefore
allow you to store more images.
The compression may be chosen before the image is taken from None (no compression),
Fine(1:4), Normal (1:8), or Basic (1:16).
Compression works by selectively discarding detail within the image which the eye tends
to overlook. As the level of compression is increased, visual effects called
"artefacts" begin to appear superimposed on the image, giving it a slightly
blurred appearance, with the grid-like pattern becoming visible in places.
The extent of this effect depends not only on the amount of compression but also on the
original subject matter. Out of focus, plain or highly random elements (sky, clouds,
trees) compress well. Animals and human subjects in sharp focus fare less well.
The final size at which the image is viewed should also taken into consideration. If
the image is to be enlarged, the compression effects become more visible than if is is
printed or displayed at a smaller size.
In most cases, the setting of "Normal" produces perfectly adequate results.
However, for fine portraiture or other critical work, choose "Fine" or, if your
camera allows it "None". For web graphics, and images that will be printed
on plain paper in reports or newspapers, the "Basic" setting is usually quite
adequate.
The compression method used is called JPEG (see What is JPEG?)
Tip: the JPEG grid pattern is spaced every 8 pixels.Therefore in an
800 x 800 image the JPEG grid is 100 x 100. If the image is printed 10cm square, the JPEG
grid pattern will be only 1mm x 1mm which will be invisible to the human eye at normal
viewing distance: The higher the ratio between image resolution(pixels) and display
resolution (pixels per inch/cm) the smaller and less noticeable the JPEG artefacts become.
