Standard Dots Per Inch?
I was recently tasked with creating two promotional banners at 850mm x 2000mm size, one of which used a bitmap pixel based image as apposed to a vector image.
I have always been unsure when it comes to the correct dpi (Dots per inch) settings for large format images. Some people say ‘save out at 72 dpi others 180 dpi and even the London Underground posters out-put at 300 dpi’, So what is the correct number of Dots per inch for large format printing?
The primary factor that determines the resolution settings for an image is of course clarity for the viewer. Billboards, banners, posters and vehicle liveries, all of which, are viewed at a further distance, use lower resolution to keep file sizes down and can still be viewed at a reasonable clarity. Although what determines the clarity is the distance a person is from the image itself.
A magazine for example will use images set at 300 dpi due to it’s very close proximity to the viewer. Posters and banners vary from 300 dpi to 120 dpi depending on where they are situated (say high up on the side of a building for example) and their overall size.
So should the standard be, 72, 100, 120, 180 or 300 dpi?
Through looking on the web and speaking to fellow designers I have come to the conclusion that there can be no standard resolution for large format printing. In the end it is down to the designers discretion to use the resolution settings which are appropriate, resulting in the highest clarity for the image to be viewed clearly.
As a guide I would recommend the following resolution settings:
Posters
A4 - 300dpi
A3 - 300dpi
A2 - 200 dpi
A1 - 180 dpi
Banners
850mm x 2000mm - 180dpi
1000mm x 2000mm - 180 dpi
2000mm x 2500mm - 180 dpi
Posted By: Dave
13 May 2009