As a rule of thumb, we recommend that artwork resolution should be 150dpi or greater at full scale for a large format print (anything A2 or larger).
If you are designing your artwork at a reduced scale (say half or quarter size) then the resolution of the artwork needs to be increased proportionally so that when the file is blown-up for printing, the quality is high enough to allow for it.
So, if setting your artwork at half size then double the resolution to 300dpi or if setting the artwork at quarter size then quadruple the resolution to 600dpi!
What if my image is not big enough for 150dpi output at full size?
When printing images at very large sizes, it is not uncommon that the original file be unavailable at a large enough size to provide 150dpi output and this does not mean that you cannot use the image! In fact much smaller images can sometimes be OK for print.
Bear in mind factors that determine if the image is acceptable:-
- The viewing distance of the image (how closely it will be examined)
- The content of the image itself (does it contain lots of intricate detail or is it a more abstract image).
Most displays have a viewing distance of at least a couple of Metres and so a large background image need not contain pin-sharp detail. If the image is abstract or does not contain precise detail then you can ‘get away’ with using a smaller image.
If your image is small then you can up-sample it in an application like Photoshop which increases the image size by splitting the pixels (interpolating) into more pixels. A byproduct of this process is the image can become ‘softer’ and it is therefore a good idea to zoom-in on the picture at approximately finished size on screen and then stand back from the display to gain an impression of what the printed result would be like.
If you have concerns about image quality then let us know about it when you submit your artwork and one of our team can take a look for you.