|
For our purposes, and simplicity of understanding, think
of an original image as one of two things:
- the real world object you are about to take a photo of.
- a hard copy photo you are about to scan to digitized
format.
In order to digitize either of these two objects, one must
sample the "original" (either #1 or #2) X number
of times within an allotted space. The accurate way to describe
this is in "Samples Per Inch" or
SPI. Generally speaking, 300 samples per inch is adequate
to create a digital image with sufficient detail to reproduce
an accurate likeness of the original. Each "sample"
is the exact same size as, and spaced equally with, every
other sample of the image so that the digitized image file
is made up of a grid map. In this respect it is akin to, but
different from, the pixels per inch, or PPI, of the monitor.
The computer converts an image file to a format the monitor
understands so it can render it for our viewing pleasure in
Pixels Per Inch or PPI. It is important
to remember that our monitor resolution is set at 800 x 600,
1024 x 768, etc. The size of a single pixel varies, depending
upon how many pixels will be available, vertically and horizontally.
If we set our monitor to display 800 x 600 pixels, across
a 17 inch screen, the image will contain fewer, but larger
pixels than if we set the monitor to display 1024 x 768 pixels
across the same 17 inch screen.
In order for us to enhance, edit, or resize an image, we
must have software capable of performing these functions.
The software industry is the largest contributor to the confusion
surrounding digital imaging. Some editing software companies
call image resolution PPI and some call it DPI; some even
have the option to re-sample an image.
Let us return momentarily to SPI. Our editing software acquires
an image file from the computer (or directly from the camera
or scanner) and actually samples the file in SPI in order
to know how to send the information to the monitor so we can
view it, however, the samples per inch the camera or scanner
used to create the file in the first place, are not the same
samples per inch the editing software uses to work with the
file. The software samples the file independently from the
original. The two could, hypothetically be equal; however,
it is not likely that they would be.
When we send an image file to our printer, the printer software
interprets the information and feeds it to the printer in
printer language so it can render it, in hard copy, on a piece
of paper. Printer language is unique to each brand and model
of printer, and is based on that individual printer's ability
to print an accurate reproduction of the image. Dots
Per Inch refers to the number of tiny droplets of ink
the machine can accurately place, per inch, on each pass it
makes across the sheet of paper. The printer's capability
is further defined in Lines Per Inch, or LPI. This is the
number of passes the machine makes per vertical inch on the
paper. For example, you may have seen the specifications for
a particular printer listed as 1200 x 600. This indicates
that the printer has the ability to print 1200 dots per horizontal
inch and 600 dots per vertical inch. The limitation of dots
per vertical inch is due to the height or thickness of the
line printed with each pass of the print head across the paper.
There are different technologies used by different companies
in producing the image that comes from our printers. We'll
cover that at a later time.
"I'll byte back."
The Pixelator
|
