and scanning can be complicated subjects. If you're like
most of us you have some knowledge of digital imaging but
aren't an expert. Please read on to learn some basics.
What is a
Digital Photos are a grid of "Pixels," or (picture
elements). Most digital photos are made up of millions of
these pixels. Pixels are tiny sections of color or tone
that together form a photograph. Each pixel is made up of
3 values; red, green, and blue, or RGB. This RGB information
is used to determine the color of each pixel. In a 24 bit
color image each of these RGB values is made up of 8 bits;
8 bits for red, 8 bits for blue, and 8 bits for green, for
a total of 24 bits. Each 8 bit value has 256 possibilities
ranging from 0 to 255. So to make a purple pixel you would
combine some red with some blue, just like mixing paint.
The RGB data for this purple pixel might be like this (red=255
green=0 and blue=220). A digital photo is simply lots of
pixels stored in a grid. This grid and it's pixels are the
basic components of any digital image. Typically, photos
are saved as JPEG or TIFF files. These files simply contain
the grid and RGB values for all the pixels in the image.
If you zoom in far enough you'll be able to see individual
pixels in any digital image.
How do scanners
work? and what is resolution?
Scanners simply read color information from a photograph
or piece of film and record this information as a grid
pixels. The amount of detail captured with a scanner is
determined by something called scanning resolution. Resolution
is measured in samples per inch or SPI. Many times people
refer to resolution with the term DPI, "dots per
or with PPI, "pixels per inch". SPI, DPI, and
PPI all describe the same thing. For simplicities sake
we'll use the term DPI from here on. So what does "dots
per inch" mean? DPI means that a scanner will capture
so many dots or pixels for every inch of area scanned.
Example: If you were to scan a 5x7 photograph at 300 DPI
you would end up with a digital image that is 1500 pixels
wide and 2100 pixels in height. Some simple arithmetic
was used to arrive with these numbers. The photo being
was 5 inches wide and 7 inches tall. The photo was scanned
at 300 DPI "dots per inch". Simply multiply
the resolution, 300 in this case, by the dimensions
of the photo
being scanned, 5 x 300 = 1500 and 7 x 300 = 2100. Resolution
determines how much information a scanner captures from
the photograph of film being scanned. The higher the resolution,
the more pixels the resulting digital image will contain.
The more pixels an image contains, the more detailed the
digital image is.
Most of us have heard the term Megapixels. Today digital
cameras are rated by a term called Megapixels. Megapixel
means 1 million pixels. In the example above we determined
that a 5x7 print scanned at 300 DPI creates a digital
that is 1500 pixels wide and 2100 pixels high. If we multiply
the width by the height we can determine the number of
this image would contain. 1500 x 2100 = 3,150,000. So the
image in this example would contain 3,150,000 pixels.
would be just over 3 Megapixels.
Higher scanning resolutions will definitely capture more
detail during scanning but the highest resolution possible
is not always the best way to go. To determine the best
resolution for scanning you must consider what is being
scanned. Ideally we want to capture every detail contained
in a photograph or piece of film. However modern scanning
equipment can capture more detail than some films or prints
contain. Scanning beyond the detail contained in a given
image only ads more data without any extra detail.
Prints typically contain no more than 600 DPI worth of
detail so scanning at higher resolutions is not necessary.
However slides and negatives contain much more detail per
square inch and thus need to be scanned at much higher
resolution than prints. The amount of detail a slide or
negative contains varies with film type and film speed.
will I need?
To determine what resolution you will need you should first
consider what you wish to do with your digital images.
you wish to view them on a computer or wish to e-mail them
to friends and family, your needs will be different than
someone who wants to create 11x14 prints from a digital
click here for help with resolving your resolution needs.
This page is meant as an introduction to digital imaging.
Don't worry if some of the things here are a little
Needs & Resolution" page will help you assess
your needs and determine which service will be best suited
to your needs. To visit this page click