Print Resolution Calculations
  
The User can decide what size to make his print with the help of the first table and notes below if required, and he can judge the resolution for printing from the final table. With these two figures and the Print Resolution Calculator he can find the third number which can then be entered into his image editor's Image Size dialogue.

Note:
Changes to the resolution, the pixel count and the print size are all made in the 'Image Size' dialogue of your image editing programme. Often this will show image size, print size and resolution and will make the same calculations which the Print Resolution Calculator makes. In this instance the calculator can provide a check that all is well. Sometimes not all three settings will be available, the calculator can then help find the right setting to enter.

If you are in doubt as to where the Image Size dialogue is in you image editor and how to change the settings, please refer to your manual.


The Print Resolution Calculator

This calculator can work out the numbers for you - it can't change your image but it can provide a check for the changes made by an image editor...and it's quite fun to play with!
Click on the link above and have a go.


Choosing a Print Size

Common paper sizes in portrait orientation with dimensions in both inches and millimetres.

Paper Size Width (in) Height (in) Width (mm) Height (mm)
A6 4.125 5.8 105 148
A5 5.8 8.25 148 210
A4 8.25 11.7 210 297
A3 11.7 16.5 297 420
A3+ 13 19 329 483
A2 16.5 23.4 420 594

Most inkjet printers will have a maximum print size of A4. The dimensions can be used as a guide in the Resolution Calculator which will accept both inches and millimetres.

Don't forget the print border. Some printers will print to the edge of the paper so the size of a print can be the full size of the paper. If your printer is not one of these, or is not set to print borderless prints, allowance must be made for the border when deciding on a print size.


Resolution Suggestions

If your Image editor allows you to set this figure for an image, setting it will allow you to print at 100%.

Each and every inkjet printer has a natural printing resolution normally dependent on its make. The quality of its output can be improved by always printing with a resolution which is a simple fraction of that natural resolution.

PrinterNatural dpiAcceptable Print Resolutions
Epson 720dpi 180 240 360 720
Canon 600dpi 150 200 300 600
Hewlett Packard 600dpi 150 200 300 600

Experimentation can be helpful in determining which resolution is the most suitable although the subject matter has some bearing. If a piece of artwork has lots of 45 degree lines and thin drawn circles then the higher the resolution the better. The red numbers in the table above provide a good starting point and it may never be necessary to change from one of them.


Pixel Count

The Pixel count refers to either the width of the image in pixels or its height. Use the more important of the dimensions for your initial calculations and the other afterwards to ensure the image is not too large for the paper.


copyright © tony cropper 2006