IMAGES

WORKING WITH IMAGES

BITMAP IMAGES

Images created using a digital camera or scanner are bitmaps. These comprise of pixels of various colours. The higher the number of pixels, the greater the resolution and therefore the better the quality of the image. High resolution images produce very large files which are more difficult to work with and slow down processing speeds. It is therefore important to use images of the optimum resolution for the process involved. When preparing a website the optimum resolution would between 72 and 96 dpi as monitors have a low resolution and the speed of processing the page is important. Printing requires a much higher resolution, between 150dpi and 1200dpi depending upon the process being used and the type of image.

The suggested optimum resolutions below apply to the image at the final finished size. If the image being scanned is larger than it will appear in its final position within a document it will need re sampling to the correct resolution within the application being used.

Black & White
Line-art

Greyscale

CMYK

Type of
Original
image

Line-art images

Image 1
standard image

Image 2
detailed fine image
with text

Line-art Greyscale CMYK

Optimum Scanning
Resolutions

For Offset Litho                     1.      600 dpi                                    300 dpi*                                     350 dpi
                                                 2.     1200 dpi

For Digital Print                     1.       600 dpi                                    350 dpi                                      350 dpi
                                                 2.     1200 dpi

For Large Format**             1.       600 dpi                                    200 dpi                                      200 dpi
                                               . 2.       600 dpi

* Brighten images to be printed on an uncoated stock to compensate for dot gain
** A table giving further resolution advice appears on the Large Format information page

Low Res
Line art

Low Res
Greyscale

Low Res
CMYK

Correct Res
CMYK

Correct Res
Line art

Scanned Text converted to JPG

Correct Res
Greyscale