A guide to printing terminology

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After many hours work you’re finally happy that your design masterpiece is good enough to set in stone, or in paper at least. You’ve searched the internet and found a reputable company to print it. Now all you need to do is prepare your file for print…

Most printers these days will accept a variety of file formats, but will recommend using a print ready pdf. Whichever format you decide to use, the way you prepare your file for print will affect the final output. The closer you stay to your printer’s recommendations, the less you leave to chance. Here is a (non-exhaustive) guide to some of the printing terminology you might encounter.

Bleed

Nothing to do with blood, but something to do with paper cuts:

What is it?

Bleed is the technical term used to describe a background colour or image which runs off the edge of the page. The amount of bleed can vary depending on how the press has been set up, but we ask for print files to be set up with 3mm bleed, that is to say, all background colours and images need to run off the edge by 3mm.

Why do you need bleed?

Bleed is used to ensure you get the best possible printed output. When materials are printed on a press they are usually printed on sheets which are larger than the finished product size and then cut down to size afterwards. This means for each “turn” of the press, not just one but several items can be printed at a time.

Once the sheets have been printed, the stack is cut, and trimmed to the desired size. This is where bleed becomes necessary. When the blade presses on the stack, it may cause the stack to move very slightly. Bleed ensures that if the stack were to move, any background colours or images would still run to the edge of the page, and no white space would be visible.

How to add bleed?

This all depends on what software you are using to prepare your artwork. With graphics packages such as Adobe Illustrator, or Adobe InDesign, you have the option of setting the amount of bleed when creating the document. Bleed can also be set whilst saving as pdf.

If you are working in a pixel based package such as Adobe Photoshop, you may need to create your page at a size which includes the bleed – that is to say, if you are designing an A5 flyer with a finished size of 148mm x 210mm and you need 3mm of bleed, you should create a page which measures 154mm x 216mm (3mm bleed on each side).

Programs such as Microsoft Publisher also have an option for you to set bleed within the advanced printer settings.

Crop Marks

Nothing to do with mysterious circles in corn fields, all to do with crosses in the corners of your artwork.

What are they?

Crop marks are the funny looking half crosses you sometimes see in the corners of print ready files. They determine where the edge of the page is (and where the bleed starts) and where printing needs to be cut.

How to add crop marks?

If you are working in a graphics package such as Adobe Illustrator or Adobe InDesign, you will have the option to add crop marks when you save your final artwork as a pdf file.

If you are using Photoshop, you will have already set your canvas size to incorporate the bleed, and you can create guides to show where your artwork area ends and your bleed space begins. When you are ready to prepare your file for print, you can get a visual idea of your bleed area, by going to Photoshop’s File menu. Click on the “Print with Preview” command. Now, tick the box that says “Show More Options”. Finally, tick the “Corner Crop Marks” box, and click the Bleed button. Specify what size you want the bleed area to be (in this case 3mm) and now your bleed area will show up on your canvas.

Colour space

Different media use different colour systems or colour spaces to produce colours. Examples of these are:

RGB
CMYK
PMS

What is RGB?

RGB is short for Red green blue. TV screens and monitors emit red, green and blue light to form the colours we see. Each colour channel can have up to a maximum value of 255. The three colours of light combine together to form white light. This is called subtractive colour synthesis. Because the system uses light, RGB colour is only suitable for use where an element is to be viewed on a screen. For this reason, care should be taken when using for print, photographs which you have taken on a digital camera, or scanned and any images which have been gathered from the internet as they may well have been saved in an RGB format.

The following file formats are RGB
gif
png
jpeg (if saved for web)

Some design and printing apps will convert any RGB elements to CMYK during the save for print process but the final result will not be within your control. When rendered using CMYK inks, RGB colours can appear quite drab.

How to convert RGB elements to CMYK

In Photoshop, open your image file. Then select Image>Mode>CMYK. You will notice that some of the colours become duller. This is because there are less colours which can be rendered in CMYK than RGB, and also because RGB emits light to create colours where as CMYK absorbs light to create colours. In Photoshop you can now adjust any of the image settings to obtain the colours or effects that you would like. Click ‘Save’ when you are ready. Your file will now be in CMYK. If you have a lot of images to convert to CMYK, you may find it beneficial to create a macro (recording of sequences) to automate the process.

What is it CMYK?

CMYK is short for CYAN MAGENTA YELLOW and BLACK, which are the ink colours used in process printing. The coloured inks are absorbed by the paper, and when combined, form a very dark black. This is called additive colour systhesis.

This colour has a CMYK value of 78/18/25/13.

This means the colour mix is made of 78% Cyan, 18% Magenta, 25% Yellow and 13% Black.

Why do you need to use it?

The printer uses software to split the colours in your artwork file into single colour cyan, magenta, yellow and black plates. These are then used to determine the amount and distribution of each colour to be printed. Each sheet is exposed to 4 layers of ink, which go to make up the full colour process.

Some printing software will convert all colour elements into CMYK prior to going to print, but the final results are not within your control. By creating your artwork within a CMYK colour space, you are ensuring that the colours are rendered on the page as you intended.

How to implement a CMYK colour space

This will depend on what software you are using to create your artwork. In Adobe Illustrator and Photoshop there is an option to determine the colour space when creating new document. If you are working in an existing document, the colour space will be shown in the tab alongside the document title. To change the colour space within a file, go to File > Document colour mode and select CMYK.

What is Pantone?

Pantone is a colour matching system which uses pre-mixed inks (similar to paint used for home decorating). There are a number of different ranges for colour types- metallics, pastels, fluo etc and paper types – coated, uncoated etc. Each Pantone range has its own colour book of physical swatches. This is great if you would like to identify and use a colour you have on an actual object rather than a computer file.

Why use it?

Pantone allows for more certainty on printed colour output. Companies and organisations reference pantone colours within their brand guidelines to ensure brand continuity. However, using Pantone colours can have downsides:

  • Cost
    Pantone colours need their own plate, meaning that artwork containing pantone has to be run separately on its own press.
  • Flexibility
    Often artwork contains not just branding, but CMYK elements such as photographs and other images. Jobs like that would need to be run as CMYK. This means that the Pantone colours in the file would either be converted to CMYK, or would have to use additional plates and be run separately.

How to use Pantone colour

When using Adobe software, Pantone colour libraries can be accessed via Swatches > Open swatch library and selecting the correct Pantone library for the application. There is a Pantone library for coated substrate (usually gloss or silk finish paper) and uncoated substrate (eg. letterhead paper such as Conqueror). This is because the paper finish can play a part in the way a colour is rendered. You can then search for the required Pantone colour reference using the search feature, or you can choose a colour from the colour palette. Once you have made your selection you can save the colour to your working palette and if you have other projects to complete, you can even save it to your library so it is available across different apps.

Pantone versus CMYK

Pantone

  • Great for colour fidelity across a range of media
  • Easy application of brand guidelines
  • Output not affected by change of print supplier or kit
  • Expensive – does not allow for batch printing
  • Not always offered as standard
  • Can be even more costly if combined with full colour process (where photos are used alongside brand elements)

CMYK

  • CMYK colour can vary depending on finish
  • CMYK ouput can vary depending on supplier and machine calibration
  • Offers good value for money
  • Does not require its own print run
  • Readily available
  • Ideal for use with mixed content – branding and images

What is Rich black?

We have seen above that in process printing, the K value determines the amount of black ink which is used. So, 100%K should give us a perfect black, right? In theory, yes, however in practice, 100%K will still look a bit flat. This is partly to do with the white of the paper “shining through” the ink (which helps some colours look more vibrant), and also because of light reflecting from the surface. In order to make your blacks blacker, you can use rich black. Rich black combines 100%K with around 25% of each of the other 3 inks. Discuss with your printer what percentages they recommend, as different paper types work better with different saturation levels.

 

What is resolution?

The resolution of an image is measured in dpi (dots per inch) and essentially refers to the amount of data which an image contains. The higher the dpi, the more information or detail. There are standard recommended resolutions for different working environments. Usually, where something is being designed for on screen viewing (website, or online pdf), the recommended resolution would be 72dpi. This is to reduce load time, and also because typically anything higher than this cannot be rendered by a standard computer monitor. Of course, HD and retina screens mean this is not always true, however load time is still an important factor.

For standard printed matter, images should be 300dpi in order to give a crisp output. Anything lower than 180dpi will look fuzzy or pixelated. Anything above 400dpi will be lost, as the output is limited by the capacity of the printer.

For large format printing, it is often recommended to limit image resolution to 150dpi at the finished size. This is a strategy to reduce file size (plus it is often difficult to source large format images at 300dpi). Also, large format printing is often designed to be viewed at a distance, so sharpness is less critical.

How to check the resolution of an image.

If you are working in Adobe Illustrator or InDesign, place the image onto your artboard. Select the image to see the resolution displayed in the top right hand corner of the screen.
If you are using Photoshop, select image>image size.
If you are preparing elements to send to a designer and cannot check image resolution in an app, you can get a reasonable idea of the resolution by checking the file size. Images of 2mb and over will usually be OK to print, depending on the size you would like to print them at. Images below this will be more suitable for web use.

Is it possible to change the resolution of an image?

It depends! It is always possible to lower the resolution of an image. An image once scaled to suit your design, may end up with a very high resolution value. As mentioned earlier, anything much above 400dpi will not be expressed by most printers, so in order to remove unnecessary bulk from your file – especially if your design contains lots of images and pages, you may choose to rasterize the image at its new scale. When you do this, make sure you choose 300dpi (if you are preparing your file for print).

If you are preparing images for web use, you should export or save for web, which will resave them at 72dpi.

Increasing DPI

When designing for print, it is possible to increase the dpi of an image by scaling the image down. If your image is already small, however you will not be able to increase the dpi in this way.

Image editing software will allow you to save a small web image at 300dpi, however doing so will only increase the file size and will not increase the quality or resolution of the photo.

 

Still not sure?

If you have any other questions about preparing your file for print, please get in touch and we will be happy to advise.

About us and this blog

am:pm graphics is a graphic design partnership based in Buxton, Derbyshire. We offer a range of quality, affordable graphic design solutions for print and web, helping our customers achieve a consistent professional identity across a variety of media.

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