[Derris]

Hi.
I need to produce a banner which will be about 2m by 2.5m high. The spec from the printer says to produce the artwork at a quarter size and 600dpi so they can enlarge it. I'm just concerned about some of the photos I'm going to use.

For example, one is going to end up about 50cm square. The photo that was taken was originally 144dpi and about 45cm square in size. I have resampled it in photoshop to 300dpi and on the quarter size artwork it will be about 12cm square. I'm using indesign cs3 and the printer said a hi res PDF will be fine, but how do I produce a 600dpi PDF from indesign? Or do I need to make sure that all the images I use are actually 600dpi? I just want to make sure the photos will be ok when enlarged ss I'm not to familiar with the process that will be used.

[Arhiann]

Originally Posted by Derris

Hi.
I need to produce a banner which will be about 2m by 2.5m high. The spec from the printer says to produce the artwork at a quarter size and 600dpi so they can enlarge it. I'm just concerned about some of the photos I'm going to use.

For example, one is going to end up about 50cm square. The photo that was taken was originally 144dpi and about 45cm square in size. I have resampled it in photoshop to 300dpi and on the quarter size artwork it will be about 12cm square. I'm using indesign cs3 and the printer said a hi res PDF will be fine, but how do I produce a 600dpi PDF from indesign? Or do I need to make sure that all the images I use are actually 600dpi? I just want to make sure the photos will be ok when enlarged ss I'm not to familiar with the process that will be used.

If your artwork is to be quarter size at 600dpi, then logically the side doubles in size when at the correct size. Using some simple examples:

a) side of 1 - area is 1x1 = 1
b) side of 2 - area is 2x2 = 4

therefore logically (a) is a quarter of the size of (b)

based on that, the real resolution when used should be 300dpi (because the dimension at the side doubles, the resultion halves).

So to answer the original question 144dpi at 45cm square (2550 pixels), translates to 129 dpi at 50cm sq. So it's not enough according to your printer. It's fairly easy to confirm though as you've already said that it's 12cm sq when used at 300 dpi which is the effective resolution that you need to use.

[Arhiann]

In theory though it should be 21.6 sq at 300dpi.

Did you get your numbers confuddled 12 instead of 21?

[Mark H]

I am not a printer, but I did design some photographic banners for my old church.

I used photographs that were mid-resolution (I am very sorry but I can't be more specific than that). I resampled them in Photoshop Elements 5 to be 150cm x 50cm to produce a banner 3m by 1m. I resampled them to 300dpi for a final result of 75dpi.

The photo banners came out well. The photos do look blocky if viewed very close up, but in my case the effect needed was for people walking past who would look at a bit of a distance.

(That may not help at all!)

Mark.