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Rastor images, such as scanned photographs, are made
up of small squares called pixels. Image resolution refers to the
spacing of pixels in an image and is measured in pixels per inch,
ppi, (sometimes called dots per inch, dpi). The higher the resolution,
the more pixels in the image. Higher resolution allows for more
detail and subtle color transitions in an image. A printed image
that has a low resolution may look pixelated or made up of small
squares, with jagged edges and without smoothness.
Image size refers to the physical dimensions of an image. Because
the number of pixels in an image is fixed, increasing the size of
an image decreases its resolution and decreasing its size increases
its resolution.
The typical monitor resolution is 72 dpi. Monitor resolution determines
the display size of an image. It is important to realize that a
computer monitor is a different medium than a printed magazine or
newsletter.
Output resolution refers to the number of dots per inch (dpi) that
the output device, such as a laser printer or imagesetter, produces.
Laser printers usually have output resolutions of 300 to 600 dpi.
High-end imagesetters can print at 1200 dpi, 2400 dpi, or higher.
The magazines and newsletters are output from the high-end imagesetters.
An image that looks fine from the laser printer may not always look
fine from the imagesetter.
Similarly, a file that looks fine on a monitor when browsing the
web, may not be suitable for printing when output from a high-end
imagesetter. Images used for the Internet are kept to a small file
size for quicker downloading and viewing. They are usually at a
low resolution, 72 dpi since that is typically the monitor resolution.
Resolution matters. Images on the web should not be saved to use
for publishing any printed matter. They are usually not the correct
image size or resolution.
This image on top is 72 dpi. It looks fine.
The image below is 36 dpi. It looks pixelated
This is the same
36 dpi image as above. It looks okay because it is displayed at
half the size of the image above to compensate for the lower resolution.
In conclusion, it is always best to send original photographs and
let us do the scanning. We can scan to the correct image size and
resolution.
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