Help please

Hi

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I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer
google me "neil barstow colourmanagement" for lots of free articles on colour management
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If the 11456px by 9450px image is a high quality image.  It does not have a A0 or A1 aspect ratio.  However, it should print well at sizes near  A0 and A1 paper size.

I echo what @c.pfaffenbichler and @Test Screen Name said, and would add that even though the .jpeg isn't the ideal format, reducing the size of it can sharpen it (reduce the pixel size, not the dpi). Image>Image Size and enter the width or height you want. Just enter the one dimension (width or height) you desire, and the other will be filled in automatically. The image will look more clear. I don't recommend over-sharpening with filters. It just adds artifacts. And as others have said, you can only reduce a jpeg, not enlarge it.

JPEG is a bad format for this. If that's all you have, you cannot make it better, but here is a simple rule: if you EDIT the file NEVER save it as JPEG. Go to a different format (perhaps TIFF or PSD) instead. Otherwise every edit will damage the file more.

Do NOT try any tricks to increase the resolution. You cannot improve this kind of image with AI or other tricks.

Ideally not jpg (or any other pixel image format) at all but vector data (ai, pdf, eps, …). 

Can you verify if a vector version of the map is available?