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Right dimensions for book cover: how to?

Jun 20, 2014, 13:27 (This post was last modified: Jun 20, 2014 13:29 by S.J..)
Post: #1
Right dimensions for book cover: how to?
Hey guys,

I'm currently preparing a present for a friend of mine. For this, I need a book cover with the following dimensions: 56cm (lenght) x 26 cm (height). I started by creating a new, blank image with that exact image size in cm. After some work, I completed the cover.

Now, I want to print this image in a print shop. It'll have to be A2-format, because of the image size. However, I'm currently very confused about the difference between print size, image size, resolution, etc.

To make it short:
- How can I make sure my image is sharp enough (aka not unreadable, it has images and text) when I print it? The Gimp tutorial advises a print size between 150-300 ppi, but my image is 64,379 x 64,379 ppi. Is this a problem? When I change the resolution, the print size also changes, which I don't want.

- How can I make sure the image retains the print size when printing it?

- In what file type should I export it?

You can view the other properties of the image in the included attachment. My Gimp language is in Dutch.

Thanks for your help!
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Jun 20, 2014, 13:46
Post: #2
RE: Right dimensions for book cover: how to?
For Gimp, the only important thing is the size in pixels. Pixels, print size and print definition are completely related:
Code:
print size=size in pixels / print definition

When you print, you want a minimum pixel density/print definition to obtain a nice, clean and sharp look. This is normally 300DPI if you have text (about 120pixels/cm). Lower definitions (around 150DPI, 60px/cm) are OK for pictures.

So yes, as Gimp is telling you, your 1419x685px images, spread over 57*27cm, will give a resolution of 65DPI, which in practice will look quite grainy or blurry. Scaling up the image in Gimp will not give you a significantly better result. The only good solution is to redo it at a bigger size.

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Jun 20, 2014, 14:03
Post: #3
RE: Right dimensions for book cover: how to?
Thanks for the reply. Redoing it will be impossible I'm afraid, this cost me hours of work. It's a bit strange that Gimp doesn't automatically choose an adequate PPI when I want to make an image in a certain size. I'm still pretty confused. So next time, you'd advice making an image with a higher resolution/ppi, and downscale it to the right print size?

How do I make sure that, when printing, the image retains the right size (56cmx26cm)? So that it doesn't stretch it out across the entire A2-page, for example.
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Jun 20, 2014, 15:19 (This post was last modified: Jun 20, 2014 15:21 by ofnuts.)
Post: #4
RE: Right dimensions for book cover: how to?
Gimp can't read your mind and doesn't know what you want to do with the image... If the image is for a web site, only its pixel size counts, and you have better work directly at the final size because any rescaling (up, obviously, but also down, to some extent) will damage the image (especially sharp edges around text and logos). So there is no "good" or "universal" default.

Now, when you create the image, you can give it a dimension in cm/inches and a print definition, and Gimp will create it at the right size (in pixels):

[Image: attachment.php?aid=3653]

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Jun 20, 2014, 15:38
Post: #5
RE: Right dimensions for book cover: how to?
Ah, I get it now. Thank you for the helpful response!
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Jun 20, 2014, 15:56
Post: #6
RE: Right dimensions for book cover: how to?
Well Ofnuts beat me again while I was doing this

so FWIW yet again

Quote: ...It's a bit strange that Gimp doesn't automatically choose an adequate PPI when I want to make an image in a certain size..

Gimp can not make that decision for you. If you choose the largest preset size File menu -> New -> A3 (300ppi) then you get what it promises: a blank canvas 297mm x 420mm you might also get a warning about the starting file size 165 MB.

Quote:..Now, I want to print this image in a print shop. It'll have to be A2-format, because of the image size. However, I'm currently very confused about the difference between print size, image size, resolution, etc.
Quote: How can I make sure my image is sharp enough (aka not unreadable, it has images and text) when I print it?

A2 is A3 doubled = 420mm x 595mm and will be a large image at 300 ppi but it is getting towards a poster and probably 200 ppi will work. Confused, then back to

Code:
print size=size in pixels / print definition

Try making a canvas like this

[Image: 529ceKp.jpg]

And Gimp does size it for you to 3307 pix x 4677 pix

Quote: ...but my image is 64,379 x 64,379 ppi. Is this a problem? When I change the resolution, the print size also changes, which I don't want.

Yes it is a problem, you have started off with a square (non ISO) size and way too large, Commercial printers are a PITA and would want something @ 300 ppi max (probably less for this size)
You need a maximum image size 420mm x (300ppi/25.4) = 4960 pix (x 4960 pix).
Then they might print it for you on A2 with empty space either side.

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Jun 21, 2014, 08:52
Post: #7
RE: Right dimensions for book cover: how to?
I really appreciate the help guys. So, let's do it right this time. I'm gonna start from scratch.

Correct me if I'm wrong, but I think I have to follow these steps:

1) Create a new image with 200-300 ppi BUT the right dimensions (56cmx26cm). See attachment.

2) Design the image from scratch.

3) Export it as PDF (necessary for printing).

4) Print in colour on A2 (with white borders, like you correctly observed). Print shop said that PPI should be high enough, resolution doesn't matter, image gets printed in dimensions that they receive in PDF.

When I follow this procedure, the PDF should have the exact dimensions I provided (56cmx26cm), and have a high enough PPI, correct?
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Jun 21, 2014, 09:34
Post: #8
RE: Right dimensions for book cover: how to?
Yes... And you can create a mock image quickly and see what PDF it produces... That will be the same size as your final image.

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Jun 21, 2014, 11:42 (This post was last modified: Jun 21, 2014 11:44 by rich2005.)
Post: #9
RE: Right dimensions for book cover: how to?
I am still a little dubious about that, the 201 ppi and the x,y resolution, but it could be just be the dialog you opened for a screenshot.
[Image: N9Ew6Am.jpg]

A PDF to send to the printer, a can of worms, and your image is still not A2 landscape size 59.4 x 42 cm

Just a suggestion, instead of using Gimp for the PDF, as well as saving, export to a png file.
LibreOffice (Draw) has an export PDF function
Set up an A2 landscape page and import your .png image.
Check that the image has not been scaled
http://i.imgur.com/muK5PQh.jpg
Export to PDF - set margins to zero if needed, turn off options.
http://i.imgur.com/oqSCS2t.jpg
and a check of the pdf properties in a PDF viewer
http://i.imgur.com/8MaM4GD.jpg

but I suspect that you might be back with questions on CMYK Smile

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Jun 21, 2014, 12:57 (This post was last modified: Jun 21, 2014 13:13 by S.J..)
Post: #10
RE: Right dimensions for book cover: how to?
Thanks again for the answers! The reason why it looks 'dubious'', with 201 ppi instead of 200, is because I'm using points/cm to change the resolution, and try to get as close to 200 ppi as possible. That shouldn't be a problem.

My image is nog A2-landscape size because it doesn't cover an entire A2-page. It's only 56 x 26cm, instead of 59,4 x 42cm. But you need an A2-paper to print it, because other paper formats won't be big enough. In practice, this would result in my image on an A2-paper, with white borders around it.

I already tried exporting my Gimp-file to png, but it rescales some of my text layers for no apparent reason? Xcf and jpeg are no problem.

Edit: I tried making a blank A2-landscape image in Gimp, and importing a jpeg of my newly created book cover (exported). This seemed to work ok.
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Jun 21, 2014, 13:16
Post: #11
RE: Right dimensions for book cover: how to?
(Jun 21, 2014 12:57)S.J. Wrote:  Thanks again for the answers! The reason why it looks 'dubious'', with 201 ppi instead of 200, is because I'm using points/cm to change the resolution, and try to get as close to 200 ppi as possible. That shouldn't be a problem.

IMHO, you are making problems for yourself, If you set up a canvas, with the size you want, say 56 cm x 26 cm and specify the ppi, 200 then Gimp will set those to the correct pixel size, maybe with a little rounding error.

Quote:My image is nog A2-landscape size because it doesn't cover an entire A2-page. It's only 56 x 26cm, instead of 59,4 x 42cm. But you need an A2-paper to print it, because other paper formats won't be big enough. In practice, this would result in my image on an A2-paper, with white borders around it.

That is exactly why I suggested using LibreOffice. There you can set up an A2 page, import your image and see what will be printed. I think it has a better PDF export as well.

Quote: I already tried exporting my Gimp-file to png, but it rescales some of my text layers for no apparent reason? Xcf and jpeg are no problem.

That is strange, only .png affected. That sort of effect can happen when x and y ppi's are different. Yet another reason to set up the canvas properly. You could probably get around it with a "layer-from-visible" then export using that or use the jpeg.

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Jun 21, 2014, 13:36
Post: #12
RE: Right dimensions for book cover: how to?
Turning the 'Save layer off set' option on solved the trick with the PNG. Thanks for the advice regarding the PPI. It seems to work now, so I'm gonna take it as it is.

I'm gonna try out LibreOffice. I also made a blank A2-landscape in Gimp, and importing my image. This seemed to work ok.
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