Large Format DPI

Hi Guys,

Can anyone shed some light on what DPI i require images to be for large format printing.

Got an advertising board 400cm x 122cm which my clients wants to place images on, I'm thinking of a selection of photographs roughly around 60cm x 60cm. What DPI will these have to be?

This will be viewed from roughly 5m on a train station platform. I know 300 dpi is for close reading/viewing.

Also if i wanted to go even bigger with my images what dpi is recommend, i have found the article below with a conversion chart is this a good enough guide?

adobe photoshop - What resolution should a large format artwork for print be? - Graphic Design Stack Exchange

Cheers Guys,
It's always best to check with the printer what they will require.

Often with large format I find they either want it at 300dpi but only half the dimensions, or 150dpi at full-size. Again, this varies so best to confirm with the printer; they'll appreciate that you're saving them time and hassle at the end.
To be honest you dont want to drop below the 300 whatever you are doing for print. I try not to. If you are working at really big size then obviously resolution comes into play to, its no good having a 300 dpi image with a resolution of 1000x1000 if you are printing onto a 3x1 meter board.

edit - yeah the usual is that you will be asked to provide it at either 1/4 or 1/2 size
I do bus backs and advertising posters and the peeps there ask for: artwork at 10% and photos, scanned images or photoshop files to be at 300dpi (they mean ppi) at artwork size. (That's for 48/96 sheet billboard work) They look fine as no-one gets close! Keep your images at 50ppi when at the final size and it should be perfectly OK.
There's an article on file resolutions here What resolution should my artwork be? | Hudson that addresses this exact subject. I hope you find it useful.

It's worth reading the whole article - if only to stop yourself using DPI when you mean PPI and to understand the importance of viewing distance - but the summary is:

"...there is no single answer to the question "what resolution do I need?". There are a few general guide rules we can highlight though. (all ppi values below are "at final output size.)

For crisp lightbox images for close up viewing, or high quality photo prints on gloss photo paper, 200ppi.
For close up poster prints, commercial lightbox work (eg. fastfood outlet etc) canvas prints, other detailed imagery 150ppi.
For standard posters, roller banners, pop up stands, close up viewed items 100ppi.
For outdoor banners and other large displays viewed from a couple of feet 75ppi.
For anything viewed solely at distance 50ppi, or lower for very large items at extreme distances."