What are the smallest dimensions/resolution I can use for a 7ft x 2ft banner?


I am designing a banner which will be printed at 7ft x 4ft.

I am using Photoshop CS4. The images are not vectors. The original poster artwork has been done at 300 ppi for A4 printing. I was hoping to re-size the canvas of the poster (after saving as a new file) to keep the 300 ppi resolution but working on a smaller scale to reduce the file size. This is mainly to avoid having to copy all the layers in to a new file to recreate the existing image.

I have looked around at various questions already on the site, but can't seem to find an answer. The common recommendation seems to be that banners or other large-scale pieces that will be viewed from a distance only need to be around 75-100 ppi, but I was hoping to work with a higher resolution and smaller size, instead of lower resolution and larger canvas.

Any and all advice or suggestions are greatly appreciated.

3/13/2013 8:48:00 PM

Decision on dpi varies according to banner positioning in space, content and printing technology. Often 100dpi is enough - but don`t take it for constant.

7x4ft in 100dpi resolution means 8400x4800px image.

For estimating image size, there are handy dpi calculators like this http://www.photokaboom.com/photography/learn/printing/1_calculators.htm#Print

3/14/2013 1:12:00 PM