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How to Reduce Resolution Using Adobe Photoshop
Image Resolution Basics
When preparing images
for the web, it is always advised to check the resolution of the source
image first. The image may be at a higher resolution than necessary
contributing to large file size and slow download times.
High resolution images
can be in the following formats. TIF, BMP, EPS PSD or JPG.
In the print world, resolution
is a measure of how many little "points" or "dots"
make up an image. When a computer screen displays an image, it is really displaying
thousands of tiny colored squares named "pixels." A computer
monitor screen displays images at a relatively low resolution of 72 ppi
(pixels per inch).
A magazine, brochure
or catalog image requires a much higher resolution image. These images
are also made up of thousands of small units called "dots."
Each dot that makes up an image is a different color.
Most hard copy publications
require images of 240 ppi or greater. Frequently, they are 300 ppi. A 300
ppi image is a high resolution image. It has more color pixels per inch &
will be of finer quality.
Since a computer monitor
can only display a maximum resolution of 72 ppi, a 300 ppi image has a lot
more color information (pixels) in the image than are necessary. If you reduce
the image resolution from 300 dpi to a web resolution of 72 dpi,
the file size will be a lot smaller and the image will load much faster.
One very important thing to keep in mind
is that when you reduce the resolution, this also reduces the
physical and monitor display size of the image.
How to check the resolution.
Select Image >
Image Size
A window like the one
below will open.
Locate the Constrain
Proportions and Resample Image check boxes. If not checked, put
a check in each box.
Under pixel dimensions
you will see the Width and Height in pixels. If you do
NOT see pixels displayed to the right of the Width and Height drop
down menus, open the menus and select pixels as shown below.
Under Print Size you
will see the dimensions in inches of the image if it were to be printed by
a printer.
Locate the Resolution:
field. It's towards the bottom of the dialog box.
Under Print Size check
the Resolution value. If the Resolution is greater than 72 ppi, change
the resolution to 72 pixels/inch.
