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Author Topic: Picture quality in pdf  (Read 107 times)

Edwerf

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Picture quality in pdf
« on: December 04, 2017, 11:49:48 am »
I just started with Scribus on Ubuntu but I am not able to get nice pictures in my pdf. The pictures are not sharp and too dark. On internet I read that you need 96 dpi only for documents printed on screen. But on my pdf I have to set 400 dpi to get sharp pictures on screen.

Could you please inform me about the minimum resolution/settings for the picture size of 572.50 pt x 246.56 pt?

utnik

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Re: Picture quality in pdf
« Reply #1 on: December 04, 2017, 02:20:04 pm »
deleted!
(it was misleading.)

utnik
« Last Edit: December 05, 2017, 06:45:17 am by utnik »

Edwerf

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Re: Picture quality in pdf
« Reply #2 on: December 05, 2017, 03:15:45 am »
Thank you for your quick reply. I don't mind about the preview in Scribus itself. I do care about the PDF output.

If I understand you well then you recommend me to:
- use an image with a minimum of 36.35 x 15.66
- create the pdf with a minimum of 225 dpi

Could you please inform me which settings you recommend me to render the PDF?
- By creating the pdf in Scribus the "Postscript" option is selected. Do you recommend to choose an other setting?
- For Compression Method I choose Lossless Zip
- For Compression Quality I selected High

utnik

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Re: Picture quality in pdf
« Reply #3 on: December 05, 2017, 06:43:50 am »
hi edwerf

If I understand you well then you recommend me to:
- use an image with a minimum of 36.35 x 15.66
- create the pdf with a minimum of 225 dpi

no! – i misunderstood the numbers from your first post – sorry!
(i'll kill my post, as it is stupid and misleading…)
i read:
Quote
…the minimum resolution/settings for the picture size of 572.50 pt x 246.56 pt?

as a strange real picturs size (in px).
now, as i read it right, i would say: for screen i wouldn't go below 100 ppi (depending on the publication/quality requirement even something between 150 and 220 ppi…)
…for your image size: at least 796×342 px (100 ppi) or up to 1752×752 px (220 ppi)

Quote
Could you please inform me which settings you recommend me to render the PDF?
- By creating the pdf in Scribus the "Postscript" option is selected. Do you recommend to choose an other setting?

unfortunately this is still the default setting for the preflight verifier. but, as you wont write .ps files, you should set one of the .pdf variants as the default ('preferences' →'preflight verifier')
…on my computer it is set to .pdf 1.3 even when i export sometimes as 1.4 or one of the .pdf/x variants (see attachment)

Quote
- For Compression Method I choose Lossless Zip
- For Compression Quality I selected High

with your settings the resulting files could be quite big – if this is no issue, that's ok. just for screen i use normally a jpeg compression…

utnik

Edwerf

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Re: Picture quality in pdf
« Reply #4 on: December 05, 2017, 02:33:41 pm »
Dear Utnik,

Thank you very much for your advise. I just updated my pictures to 250 dpi in The Gimp before I upload them to Scribus. Here I give them the same size as in the Scribus Framebox. This is a big improvement in which the quality makes me already satisfied.

Px and Pt is confusing indeed. After every mouse click it’s at Px as a standard. I will check my settings on this.

Most of my pdf’s will be read on a telephone or tablet. I am looking for the best quality as possible but I believe that the pdf size must be less then 10 mb. My documents are about 20 pages with 5 pictures as mentioned on the attachment. I am surprised that the combination automatic/high generate a smaller pdf then automatic/maximum. Hopefully I can reduce the pdf size with your recommended Lossless zip with High compression.

Thank you very much for your quick reply and advise!

With best regards,
Edwin

utnik

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Re: Picture quality in pdf
« Reply #5 on: December 05, 2017, 06:40:40 pm »
hi edwin

your page looks good!
one advice: you should use snapping guides to align your image frames.

Px and Pt is confusing indeed. After every mouse click it’s at Px as a standard. I will check my settings on this.

i work almost always in mm – for me, this is a 'more real' unit than pt…

Quote
…I am surprised that the combination automatic/high generate a smaller pdf then automatic/maximum.

'high' means high quality, not high compression!

Quote
Hopefully I can reduce the pdf size with your recommended Lossless zip with High compression.

reducing .pdf size significantly while keeping the best possible quality is usually done by reducing the resolution a bit and finding a good jpeg (lossy) compression rate.
i would generate and examine a test file with '150 ppi', 'lossy – jpeg', 'high'.

utnik

mnawij

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Re: Picture quality in pdf
« Reply #6 on: December 06, 2017, 01:09:49 am »
Hi Edwin, just a quick note:

Pixels are used when the final image will be displayed on a screen and points (and most others) when you will be printing. Adobe's standard is 72 points/inch but I believe the original was like 72.2 points per inch, they just rounded it out.  When you are trying to figure the size for pixels it is: (# of pixels) / (resolution) i.e. 600px by 600px would be a 2"x2" picture when printed at 300ppi. 3"x3" at 200ppi, 4"x4" at 150ppi, etc.

Regards,

mnawij