Artwork Setup Guide

IMAGE SIZE AND RESOLUTION

Getting good quality images when printing depend on two factors: Resolution and Size.

As a general rule images should be supplied at a resolution of 300ppi and as close as possible to the final physical size they will be printed. If your image is too small or the resolution is too low, it will appear pixeled and poor quality in the final print.

The below image is set at 300ppi; this is the optimal resolution for printing. The actual dimensions of the image are 13cm by 9cm; ideally this would be the maximum size you would print this image on the sheet to get good quality.

INTERNET SOURCED IMAGES

Images sourced from web pages on the internet will almost always have a resolution of 72ppi, which is the recommended resolution for web images, however this is usually not good enough to print from, unless it is being reduced in size considerably.

The example below is a guide to demonstrate the difference in quality of an image saved in 72ppi and 300ppi.

DIGITAL PHOTOS

Nowadays most digital cameras also save images at 72ppi; the difference with these images is that the physical size is much bigger, for example photos taken on an iPhone will be 72ppi but will be over 1.42m wide and 1.06m high. That’s quite a large image!

If you scale these images down, the pixel density increases proportionally and so the image is usually good enough to print when made smaller.

But how small?…

A good way to check the size that you can print a digital image is to use an editor like Adobe Photoshop. If you open an image and select “Image size” from the “image” menu it will show the current size of the image. If you deselect the “Resample Image” checkbox and then change the “Resolution” to 300ppi, you will see the “Document Size” figures change; these will be the actual dimensions of the image when printed at 300ppi.

In the example below the image will print at a maximum size of 34.14cm wide by 25.6cm high; if printed larger the pixels may start to show.

COLOUR FORMAT

Before submitting your artwork, please ensure your design is saved in CMYK colour mode; this is the standard colour mode for professional printing. This includes all photos and graphic elements.

Any items saved in RGB mode may give incorrect colour results when they are printed by our CMYK presses. RGB is a colour mode intended only for digital displays and web images.

Most software applications will have an option to save in CMYK format. In Adobe illustrator for example you can select File > Document Colour Mode > CMYK or in Adobe Photoshop you can select Image > Mode > CMYK Colour and then Save.

If you’re working in InDesign, you can convert any RGB images within your design by saving as a PDF and selecting the Press Quality PDF pre-set in the Save Adobe PDF dialog – then in the Output tab, select Convert to Destination (Preserve Numbers) and select a CMYK profile (usually one labelled “FOGRA 39′ which is best for European printing).

The Technical stuff

RGB is an acronym for Red, Green, Blue which are the separation colours of light, whereas CMYK is short for Cyan, Magenta, Yellow and Black (the K or ‘Key’ is a term from traditional printing where the Key colour is the plate that holds the detail in the image, in CMYK printing that colour is Black, hence the K represents the Black separation).

Because anything that is RGB will have to be converted into CMYK to be printed, sometimes colour values can change quite drastically and therefore the colour of the final print can be quite different to what was expected. This is because there are far more colours available in the RGB spectrum than there are for CMYK, so brighter colour RGB values are changed to what is perceived by the software to be the closest equivalent value available in CMYK, when in reality they are quite different.

Unfortunately, we have to use RGB computer screens to create our designs, therefore what you see on your screen does not truly represent the colour of your final print; most monitors can only provide what is a best guess to what the colour will look like. Calibrated monitors are available, which can provide a much more accurate colour simulation than standard monitors, but they are still not perfect and can be quite expensive. It’s not surprising that even experienced designers can sometimes struggle with colour differences between what they see on the screen and the final print.

To try and narrow the gap between these colour differences, Colour Profiles were introduced as a way to convert colour from one format to another. These profiles consist of libraries of values that are used as a sort of translation by the software to achieve the closest possible colours during conversion. Nowadays most printers and monitors have colour profiles either supplied with them or built in.

However some RGB colours can never be reproduced in print simply because the colours do not exist in CMYK and because of the way the colour is displayed; colours on a monitor are illuminated from behind, whereas printed colours use reflected light from the surface of the media.

Example:

RGB Colours as seen on a monitor – these colours could never be reproduced accurately by printing.

Converted to CMYK as seen on a monitor – the colours look a lot flatter and have lost vibrancy.

However all is not lost, when the CMYK colours are actually printed they will be brighter and more vibrant than ones that have remained RGB.

RGB colours printed – colours look very flat and washed out.

CMYK colours printed – colours look more vibrant and brighter.

The images here are just a visual representation, because as you are viewing them on an RGB monitor, results will differ from an actual printed image, but it gives an insight into the way colours can be affected if using the wrong colour format.