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Dpi how to work it out

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Shaun Harris

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Post Thu Jun 04, 2009 6:08 pm

Dpi how to work it out

I need to send files for printing in 300dpi. I have the resolution and number of pixels. How do i work out Dpi?
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Graeme Harrold

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Post Thu Jun 04, 2009 6:20 pm

The resolution is the DPI. If you need to alter the DPI open the file and change it in your normal editor. e.g. in Corel Photo paint open image - resample and then change the numbers manually.
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Nigel Hindley

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Post Thu Jun 04, 2009 6:36 pm

Bear in mind that altering the DPI will not really increase quality just mimic and add pixels. You are better off getting higher quality images in the first place!
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Shaun Harris

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Post Thu Jun 04, 2009 7:04 pm

Thanks guys.

Wasn't sure if res was the same as Dpi. I'm using SL8. there is an option to supersize image, I've changed the resolution to 300x300 which makes the image 70 MB (I did know the file size would go up) so I can't send it (it's a 4M banner) even zipped up it's about 15MB.

I was trying to work out which format to send it in to get a smaller file size, but needed to make sure I was doing the correct thing with the res first.
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Martin Grimmer

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Post Thu Jun 04, 2009 10:25 pm

Shaun,

Once you ahve done what you need to in Signlab, if you have photoshop, try 'save for web' (under file/save for web) - this does an excellent job of reducing file size -you can preview what it will look like beforehand.

MArtin
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Post Thu Jun 04, 2009 10:39 pm

Shaun Harris wrote:Thanks guys.

Wasn't sure if res was the same as Dpi. I'm using SL8. there is an option to supersize image, I've changed the resolution to 300x300 which makes the image 70 MB (I did know the file size would go up) so I can't send it (it's a 4M banner) even zipped up it's about 15MB.

I was trying to work out which format to send it in to get a smaller file size, but needed to make sure I was doing the correct thing with the res first.


Shaun, you do not need to save it at300 dpi final size, a 6x2 banner will be ok at 100dpi, then publish to pdf
If in doubt pop it over to me (pm your email) and I will have a look)
Pete
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Post Thu Jun 04, 2009 10:42 pm

You can use something like dropsend, to pass on large files, if you need to

Peter
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Post Thu Jun 04, 2009 10:43 pm

Martin Grimmer wrote:Shaun,

Once you ahve done what you need to in Signlab, if you have photoshop, try 'save for web' (under file/save for web) - this does an excellent job of reducing file size -you can preview what it will look like beforehand.

MArtin


No good for the printer though :(

Peter
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Post Sun Jul 19, 2009 12:31 am

Most digital printers require files of 72dpi at the size its going to be printed.
If you are enlarging the file (eg200%) then your original dpi needs to be around 150dpi...scale 400% file would need to be around 300dpi. This simple calculation means that you need to start with the image at size at the highest possible dpi...going down will keep the quality...going up (as already stated) does not increase the quality..merely increases the file size. Having an image supplied at 300dpi does not make it correct though..if the image is 300dpi at 100mm x 100mm scaling it to fit a 6m x 2m size may mean pixellation occurs (scale 2000% image = 15dpi).
to reduce file sizes save as jpg for sending.
a good ftp program is send this file (free)
or mail this file (again free)
If you are sending to a pro printing house make sure you put all items in a folder and zip it. If you send via ftp the file exchange servers need individual items to have the file extension at the end...if not they become unuseable.
Saving in a zipped folder overcomes this problem as it becomes one file ".zip"

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