Author Topic: PDF: 300 dpi wanted, only 72 dpi  (Read 10196 times)

utnik

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Re: PDF: 300 dpi wanted, only 72 dpi
« Reply #15 on: April 07, 2014, 04:10:37 pm »
hi boe

the proplem is: you need 300ppi, but you don't know the difference – and lots of people (and some graphic programs) don't differentiate between the two…

utnik
« Last Edit: April 07, 2014, 04:14:40 pm by utnik »

Nermander

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Re: PDF: 300 dpi wanted, only 72 dpi
« Reply #16 on: April 07, 2014, 04:26:27 pm »
Boe, you are saying the opposite...

PPI is pixels per inch. This is what most people really mean when they say DPI.

A digital image normally only have pixels. It does not "have" a DPI or PPI. It might have a DPI number inside, but that number is nearly useless.
(Note: I just read the JPEG is the only image format containing a field for DPI!)

If you have an image that is 2000x2000 pixels and print it at a size of 2x2 inches you print it at 1000 PPI. If you print the very same image at a size of 5x5 pixels you print it at 400 PPI. The DPI value inside the image might still just say 72 DPI.


Now, when printing a pixel the printer needs to be able to give the pixel a certain color. However the printer only contains a finite number of inks, each with it's own color. To be able to give the pixel the desired color the printer must print one pixel using several dots. This becomes the DPI value.

For example a 1200 DPI inkjet printer will usually only be able to print 300 PPI, while using 4x4 ink dots for each pixel.

Look at the illustration on this page.

http://mydigitalcamera.us/ppi-vs-dpi-resolution-what%E2%80%99s-the-diff/

This means it is virtually impossible to print a 300 PPI image with less then 300 DPI (some types of printer can print a pixel using just one dot where they mix different amounts of the inks).


Found another page with some better illustrations and more info
http://99designs.com/designer-blog/2013/02/26/ppi-vs-dpi-whats-the-difference/
« Last Edit: April 07, 2014, 04:35:07 pm by Nermander »

Boe

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Re: PDF: 300 dpi wanted, only 72 dpi
« Reply #17 on: April 08, 2014, 06:26:20 am »
Hi Utnik and Nermander,

I am just trying to conform to the tshirt printer's specification of 300 DPI.  So far all the tshirt printers I have checked out ask for the artwork in DPI. Here is an example of the specs from theprintbar.com:

"Our printers print at 600 x 600dpi or 1200 by 1440dpi (printers use only dpi) with large drops of ink."

Note "printers use only dpi".

At the end of the day Scribus has a DPI output feature but every change I make to any settings that affect the DPI still result in the default viewing resolution of 72 DPI.

You are teaching me a lot about ppi (which I appreciate  :D) but this doesn't resolve my problem with Scribus' DPI output, unless something you are saying is going over my head.

Nermander

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Re: PDF: 300 dpi wanted, only 72 dpi
« Reply #18 on: April 08, 2014, 08:58:40 am »
Read the pages I have linked to!

Quote
Today, “dpi” can also be used to mean printer droplets per inch (for inkjet printers) or maybe pixels
per inch (for photo files and full-color devices just like displays, photographic output devices,
and also dye sublimation printers). Quite simply, it doesn’t make reference to a single standard unit of
measure. That is the seriously confusing situation to get a lot of people.

Quote
Now, that being said, people say “DPI” when they really mean “PPI” all the time — so much so that it has become an established convention that you have to put up with (Apple, Microsoft and Adobe have all been guilty of this improper usage). The important thing is to be able to know whether someone is referring to actual DPI or really means PPI.

So, 9 times out of 10 (or even more), when people say DPI they really mean PPI.

utnik

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Re: PDF: 300 dpi wanted, only 72 dpi
« Reply #19 on: April 08, 2014, 09:34:26 am »
hi boe

the whole dpi versus ppi thing was initiated when you asked me if i mean ppi or dpi! (we knew that you're talking about ppi before, but we didn't mention it…)

for your initial problem, i told you all i could find in the files you provided.
  • the image of the bird in the .pdf file in the .pdf file had its 300 ppi…)
  • you didn't provide the files you are using, i had to deal with replacements (had to change your .sla file) before testing. (i asked for the 'real' files…)
yesterday you asked:
Quote
Still waiting for help on this one. Does anyone else have the answer? I'm desperate now.


so i think you're searching for someone who is willing to help without your cooperation…


utnik