8ft x 4ft poster...but how many dots per inch for images?

Question

I've read a online somewhere a while back that the bigger the end product, the less the amount of dots per inch needed. is this true? if so, when do I start changing from 300dpi for A3 sizes to smaller DPI's on larger size prints?
is there a way to calculate this? I'm always thinking it might for spending less ink on the larger size prints, etc
and what should I use for a 8x4ft poster when:
1. people are gonna see it up close
2. when the closest they get would be about 4-5 feet away
with this particular poster, people are gonna be up close.
thanks for any info

Answer 1

Was DYP wrote:
hummm....I would'nt want to work on an 8ft x 4ft banner at s/s size on a 21" inch screen, each to his/her own I guess.
I don't see where that would make any difference in working with the file, but it sure makes it convenient for printing. I work on lots of full size banners all the time. The only time a make them less than full size is when I am working on something bigger that 18' which is IDs maximum size.
But doing them half size at 300 dpi is fine to. You just need to be careful that your graphics are not to low a resolution or you will be in for some surprises from IDs output, especially if you trying res-up when printing.
I was really trying to suggest its easier to move around on screen if the artwork is not size for size.
I guess everyone has their own particular way of working. I don't even produce A2 output at s/s size. I'll do that at either A4 or A3.
I agree with the low res graphics. I don't seem to have any issues with just supplying 300dpi for any sized output to be honest. I've produced largish exhibition stands and A4 hand-outs from the same file. Seems to work ok for me.