To be safe, use 300dpi AT FINAL OUTPUT SIZE, not original image size if scanning.
Careful of your scaling.

Unless you are doing inkjet or continuous tone prints...then 200 is fine.

A2 is an ISO standard so yeah its the same everywhere, i.e. everywhere that actually recognises ISO.

Thanks for this info ... I was going to try and get away with 200dpi, because the layout is based on an A4 brochure design we already have done, and some of the images just aren't going to be ok at larger size in a poster.

I'd rather be SAFE!
Thanks again.

<shrug>

GIGO.

Sorry if I was confusing. The poster is a remake of a design that was orignally done up at A4 (300 dpi). The photographs in the original A4 sized document are fine to print at 300 dpi, but to set them up to print in a similiar design/layout at A2 is just not possible - they just dont have enough res. Sooo, I was thinking I might be able to get away with setting up at 200 dpi (A2 100%) - some of them would be ok - just.

.... but ... I'd rather be safe, than sorry, and set up at 300 dpi and do away with the lower res images ... am I still confusing!!?? Probably. Nevermind ... all i needed to know is what resolution would be advisable. I'm sticking with 300 dpi as you suggested.

hmm...I think I get the gist of what you're saying and perhaps something needs to be explained (gonna hafta bear with me)

Imagine an A4 image at 300 dpi. (dots per inch)
It's measurement in inches: is 8.267 / 11.693
and in pixels: 2480 / 3508 (300 x (8.267 / 11.693))
lets imagine that each and every one of those pixels has a different colour, it is these pixels make up the detail in your image.

Now imagine changing the resolution from 300dpi to 600dpi. for every pixel that was there before there is now 3 pixel shaped holes that surround it and need to be replaced with more pixels (take a square and cut it in 2 down both axes...you now have 1 + 3 squares), how does Photoshop know what colour to make those pixels and remain faithful to the image?...it doesn't.

All Photoshop does is compare pixels that surround those gaps and choose a colour that fits. Basically upping the resolution does not improve the level of detail it merely adds more pixels...the colour of these being determined by those that are near it.

When you see programs on T.V where people take a crappy image and *enhance* it so that they can now see the freckles on what was once a 20 x 20 pixel face it's complete bollox. If the information does not exist to start with the program isn't going to add any itself. (with heuristics a program may be able to draw some inferences when working with primitive images or patterns, but heuristics or not...there are no algorithms that can add this sort of detail)

How this pertains to your problem...if your image at A2 prints like a bag of spanners...no end of resolution tweaking or wizardy is gonna fix it...you need to get an image that has more information to start with. (ie: your original image needs to be greater than 300dpi)

http://graphicdesignforum.com/forum/...read.php?t=294

^read^

GIGO = Garbage in Garbage Out.