| Digital
Photography Professional Development class PowerPoint outline
These files are in
PDF format:
The
following notes about digital imagery were created by Ken Russell. If you have questions about
this topic, or would like to see more information about a
particular aspect of it, you are welcome to contact him by
email.
Think
ahead about how you will use an image before you take it:
- If you plan
to print the image, you will
want to set your digital camera
to a higher image resolution
that is based on the resolution
of the output device (usually
a printer).
- If you plan
to put the image on the web,
you will want to use a low image
resolution setting on your digital
camera.
- If you want
to do both, use a high resolution
setting on the camera, then transfer
the image file to a computer.
Keep the high resolution image
for printing and resample a duplicate
image to
a lower the resolution for use
on the web. You will then have
both a high and low resolution
version of the same image for
different purposes.
Image
Resolution
The
term resolution in reference
to images refers to the number
of pixels (points of color) that
compose an image and determine
its detail. Resolution is determined
by the pixel dimensions of the
image—the
number of pixels along the width
and height of an image. The higher
the resolution, the more pixels
the image contains.
Image
Size:
Refers to the
dimensions of the image. It can
be expressed in pixels (for example:
800 x 600 pixels), or by inches.
If it is expressed in
inches, the output resolution must
also be noted. For example, an
800 x 600 pixel image will print
at 2.6" x 2" on a printer that
prints at 300 dots per inch
(800/300 x 600/300). It will print
at 5" x 4" if the printer prints
at 150 dots per inch.
Monitor Resolution
Monitor resolution refers to the
number of pixels that can be
displayed on a monitor. It is
expressed in dots per inch (dpi).
Most monitors are about 72 dots
per inch (dpi), but they can
vary somewhat.
Image File Size:
The higher the resolution, the
larger the file size of an image.
Image file size, usually measured
in kilobytes or megabytes, is
proportional to image size, but
varies depending on the file
format (whether it is a JPEG,
TIFF, etc.). The lower the image
resolution, the more pictures
you can store in the camera.
The higher the image resolution,
the less images you can store.
Camera
megapixel rating—how much
is enough?
How
many megapixels should a digital
camera be rated for in order to
produce a picture of a specific
size? This table shows the megapixels
required for common sizes and
outputs:
|
Print Size
|
Web Page
(72 dpi)
|
Low-Resolution
Printer (150 dpi)
|
High-Resolution*
Printer (300 dpi)
|
|
4" x 6"
|
0.12 MP
|
0.54 MP
|
2.16 MP
|
|
5" x 7"
|
0.18 MP
|
0.79 MP
|
3.15 MP
|
|
8" x 10"
|
0.41 MP
|
1.80 MP
|
7.20 MP
|
|
11" x 14"
|
0.80 MP
|
3.47 MP
|
13.86 MP
|
Green numbers
indicate images that can be taken
with a 3 megapixel camera.
*There are
even higher resolution printers—600
and even 1200 dpi. 300 dpi is typical
for non-professional
output; 300 dpi looks pretty good.
Digital Camera Suggestions
- To take good
digital pictures, you should
begin by thoroughly reading the
camera's manual.
- Disable
the digital zoom, it degrades
image quality (the manual zoom
doesn't).
- Most digital
cameras save images in the
JPEG format by default. For
high quality printed images,
change the file type setting
on the camera so the
image is saved as TIFF or RAW.
However, this will considerably
increase the file size. An
alternative is to set the JPEG
quality high, but there
will still be some quality
degradation. If you are unsure,
run tests at various settings
and carefully examine the results
from the output device you
will be using.
References
Resolving Resolution: www.mkprod.com/ResolvingResolution.htm
About
Resolution: www.ltlimagery.com/resolution.html
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