Technical Help & Information

What size image is right for me?
For best quality in the finished product you should choose the right image size when you buy an image from Guidescapes.com. If you are going to display the image on a computer monitor (for example on your website or on a CD-ROM), then choose Low-Res when buying your chosen image. If the image will be used in a printed publication, then choose Hi-Res or Super Hi-Res depending on the final size (in millimetres or inches) of the printed image. You should choose your size carefully, because you cannot scale a lower resolution picture upwards, without a significant loss of quality.

The table below will give you an idea of the standard dimensions of our images. However, certain printers will be able to successfully reproduce images at much larger sizes. Ask your printer for more information.

Image Size Guide Low-Res 72dpi ± 1000 x 650 pixels on screen ± 8.5cm x 5.5cm printed Hi-Res 300dpi ± 3300 x 2100 pixels on screen ± 28cm x 18cm printed Super Hi-Res 300dpi ± 6600 x 4200 pixels on screen ± 56cm x 36cm printed

Image Colour Formats
Images intended for display on computer monitors are best saved with an RGB colour profile, while those intended for print are best saved with a CMYK colour profile. These profiles can be changed later in your image editing software.

Colour Profiles of Guidescapes Images Low-Res RGB Hi-Res CMYK Super Hi-Res CMYK

File Sizes
Approximate sizes of final downloads are provided here for reference (file size will vary according to your chosen image):

File Size Guide Resolution JPEG Zipped JPEG Low-Res 700kb 700kb Hi-Res 5.2MB 5.1MB Super Hi-Res 13MB 12.7MB

What is the difference between pixels and dots per inch?
Pixels per inch (PPI) and dots per inch (DPI) are both measures of the resolution of an image, and are often used interchangeably.

Pixels per inch refers to the resolution of an image when it is viewed on a computer screen. For example, if an image is 72 pixels wide, then it will take up 72 pixels on your screen. So if your computer screen has a resolution of 72 pixels per inch, then the image on screen will be 1 inch wide. The resolution of computer screens does vary, but most commonly it is 96ppi, or 72ppi for Apple Mac screens.

Dots per inch is technically relevant only when printing. Graphic designers and printers normally aim to use images with a resolution of 300dpi, which means literally, there are 300 of the smallest units (dots) available in every inch printed. Any less and the image may be ’pixelated’. Any more is superfluous and just makes the filze size very big. Nowadays, most images being prepared for printing start off as a digital image, and so a pixel and a dot will be the same thing.

A third term, Lines Per Inch (LPI) is sometimes used to describe the resolution of the printer. Machines that print newspapers commonly have an LPI of 80, meaning in every inch the printer is capable of printing 80 distinct lines horizontally or vertically). Most print jobs will be produced at 150lpi. Graphic designers and printers double the LPI to obtain the ideal resolution for their images. Hence when we double 150lpi, we get 300dpi. This seems to produce the optimum quality for that particular printer. It is quite possible to use a 150dpi image on a 150lpi printer, although this is not recommended if the quality is important.

In short:
PPI - describes resolution of on-screen images
DPI - describes resolution of printable images
LPI - describes the printing machine’s capbabilities