Resolution confusion

[wizzpig666]

Hi Guys

My first time posting here. Hopefully I've come to the right place

I have been asked to design a sign that will have a final dimension of approx 2metres x 3 metres. My confusion is twofold:

1. What image size should I be working at and at what resolution? Is there some formula for calculating working format compared to final output ?

2. The layout will include some photographs. The final output of the photographs could be around 500mm x 1000mm or bigger. How do I know if a photo I intend to use has good enough resolution? eg if I have a photo with 1728 x 1152 resolution , how can I calculate the maximum output size of this photo with good resolution.

Many questions I know but much head scratching going on here!

Any help would be much much appreciated !

Thanks

 

[Hi_Fi_Guy]

Your resolution should be 2x the LPI of the printed sign (@ 100%). As an example, a typical magazine has an LPI of 133 - 150 so most people use 300dpi images. A billboard may have an lpi of 12 so a 24 dpi image is plenty (again @ 100%).

Next calculate the reduction from the physical size to the dimensions you intend to work on and multiply the results to get your DPI. A billboard size image reduced to 11" wide may end up being a 400dpi file.