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Some commonly used formats:
|tagged image file
|graphic image file
|.jpg / .jpeg
The file size of the same image -- same size, seemingly same quality --
can go down from a 650 KB bitmap to a 16 KB compressed jpg.
Obviously, the latter loads faster. See various image formats and same image with different rates
The compression rate varies according to the quality of the original
image. A high quality image, such as that of the zebra, may be
compressed 70% for computer display without appreciable loss of quality.
Therefore, for a computer or web page, you should use compressed images
in .gif or
size, image size, resolution:
To see the FILE SIZE, find your image file with Windows Explorer, with
View Details selected.
To see the IMAGE SIZE, open the image, right-click, click Properties.
It will give you the size in either pixels or inches. Yes, Virginia,
you can FORCE the image into a smaller space by changing the box
containing it in your document or web file -- this will keep you from
having to scroll but will not decrease the file size.
To do this properly, you should RESIZE the image to the desired height
and width. You can do this for a single or a number of images in
one go with Photoshop, PaintShopPro, or, most easily, with Digital
Photo Slideshow software -- see below.
RESOLUTION is the other factor that affects file size. Digital photos
or scanned images may have a very high resolution suitable for high
For a computer or web page, you should have a resolution of between 72
and 96 dpi, in .gif or .jpg compressed format. Again, the three
software packages named above will let you do this, for individual or
sources: see | Scanning |
Photography | more
on photography | Photography
Download images from the Web or copy them from a CD but
make sure to do so legally and with permission and credits.
creating and editing software:
(basic and free; it comes with MS Windows)
Picasa Photo Management (free from Google, for the time being --
download and install): http://www.picasa.com/
affordable and very good: Jasc
PaintShopPro, Adobe Photoshop Elements, Ulead PhotoImpact
and excellent professional package but hard to learn: Adobe Photoshop
-- you can resize, change format, create a slide show,
and much more: free download, $20 to buy.
Check out Impatica
easily compress a PowerPoint presentation for the web -- my 70 MB file
changed to a 2 MB file.
of image editing: edit an image,
or in PhotoShop
good web pages on graphics
(Great Images in NASA Library of Images)
Ursula Hoffmann -- last rev.