Oamaru Print Logo

The designer's guide to printing a poster

Make sure what you designed on screen is accurately reproduced on paper, with our pro's guide to poster printing.  

Taking digital designs to the real world can be fraught with gotchas and gremlins along the way. We’re oh-so-used to the world being digital that we’ve mostly forgotten how to prep our work for poster printing. 
If you’re thinking of doing a run of posters for a campaign, party, gig or simply to adorn your own walls with, here’s a top lined guide to how to print a poster. Follow our tips and you'll soon be poster printing with confidence - and you'll no longer have to worry about that guy in the print shop laughing at you... 

If you're producing your own poster designs with the intention of taking these to a poster printing shop then make sure you're working in a CMYK colour space rather than RGB. In Photoshop you can easily switch to this mode via the Image>mode>CMYK color menu command to give you a more accurate representation of how your colours will print.

Converting to CMYK 
If you’ve been working in RGB and have converted your work to CMYK just before you send the file for poster printing you’ll notice that the greens and blues in your image become lifeless and dull. 
You can use Photoshop’s Gamut warning tool (View>Gamut warning from the file menu) to highlight the colours which will have trouble converting from RGB to CMYK. 
The RGB colour space has a greater array of colours than CMYK. If you imagine that all the computer specific colours you pick in Photoshop for your poster then have to printed with a selection of real world inks. If these can’t print some of these colours they become “out of gamut” of what is possible with ink. 

Set the right resolution
Print files are BIG. One of the most common delays in a poster printing job is caused by work being sent back by the printer because the resolution was too low. Files destined for print should be set to 300dpi. DPI stands for Dots Per Inch. Simply put the more dots to make up the image the higher the resolution. More printed dots in an inch means higher quality reproduction. 
When resolutions are too low the end result can be a blurred and pixelated poster. In Photoshop you can set the dots per inch on creating a new document File>new and entering 300 in the Resolution box. 

Set the right size for poster printing 
Popular poster printing sizes are A2 (594mm x 420mm), A3 (420mm x 297mm) and A4 (297mm x 210mm). Paper choice and weight can be discussed with your printer but 170gsm Silk or Gloss Art FSC or 150gsm are good choices. GSM stands for grams per square meter and determines how heavy the paper stock is. 

How to supply your files
Supply your print files in the PDF format (print resolution at 300dpi) or tiffs with no compression at the same dpi. You can send jpegs if they’re high res enough and if you just want a poster printing of your pet pooch from your smartphone you can do this as well by sending a jpeg but be warned bit around the edges of the photo will be cut off and the colour will shift.

What is litho printing? 
A wide variety of mass produced print item (books, posters, newspapers etc.) are produced using litho printing. Put simply a litho print involves the printer making a set of “plates” which are used to press the image to the paper. 
Creating these plates is at a cost and doesn’t offer the immediacy of digital poster printing. The initial outlay can be expensive but if you’re doing a large print run and want to output up to A1 it’s the process which offers a higher quality print and finish than digital printing. 

Digital vs litho printing  
You have two choices for poster printing: digital or Litho. (Well, okay you have three: you can always print at home. But chances are you don’t have a printer big enough.) 
The choice between digital and Litho printing will mostly be dependent on the money you have for the print job and how soon you need it doing. Digital printing with inkjet or laser printers is the cheaper and quicker of the two and good smaller print runs. If budget is an issue and you’re not being too exacting over the quality as well as not printing above A3, go with digital printing. 

Choose the right poster printing shop
Different printers have different levels of expertise, so it's worth doing your homework and getting personal recommendations. Also make sure you tailor the printer to the job at hand.

The importance of spellcheck
We advises that you, "spellcheck, spellcheck, spellcheck. Then get your mum to spell check it and anyone else who will read it for you. There's nothing more soul destroying than a typo and they're easy to miss if you're too close to your masterpiece."

What is 'bleed'? 
'Bleed' is simply a little bit (usually 3 or 5mm) around the edge of your poster design which (depending on how the printer cuts the paper down) may or may not be shown in the finished result. It's essentially your room for error and ensures there isn't a random white line on the edges of your poster printing. 
Programs such as InDesign and QuarkXPress make it easy and will show guides, so you can see where the bleed starts and finishes. Always ask the printer you're using (or check your own printer settings) to determine how much bleed is to be given. 

What is 'trim'? 
The trim is the edge of the final printed output. To prevent text and logos being chopped off the final output they should be placed with some breathing space around them and no closer to the Trim Edge than 1/8in. 

Use vectors
Designer Franz Jeitz advises: "When it comes to printing, especially large format printing, vectors are your friend. Try to design as much as possible in a vector based program such as Adobe Illustrator. Not only will it reduce your file size, but it will ensure that you get the crispest print result."

Check your fonts 
Always run a pre-print check. In InDesign this is known as a “Pre-flight” This will bring up any issues such as RGB files being used or fonts used which aren’t embedded. InDesign can package up all your print files and links (File> package) into one folder which will spare you any missing font nightmares. 

Get your blacks right for poster printing
When printing posters using black, there are so many different types of black you can use (RGB, Photoshop, neutral rich, registration, flat, designer, etc.) 
My tip would be to avoid using RGB black as this is primarily used for the web/digitally and will look washed out and grey in print. Which black you should use will depend entirely on your poster printing process and what paper stock you're using, especially if you're printing solid blacks. 
When I designed a recent infographic piece, I spent days printing various different blacks on different stocks of paper to get the most accurate black whilst making sure the colours didn't bleed into each other, a really lengthy but worthwhile process! Always leave plenty of time to test your blacks; it can completely ruin a fantastic poster design if you don't.