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Scribus => Raster and Vector Graphics => Topic started by: mnawij on April 01, 2019, 02:39:46 am

Title: import image max resolution
Post by: mnawij on April 01, 2019, 02:39:46 am
Is there a maximum resolution for imported images? I keep getting an exclamation point whenever I am importing a 3200 dpi bitmap image.  I understand that it is part of the preflight checking, but when I edit the max image resolution in the preferences->preflight to 4800 dpi, I am still getting the red exclamation point.  Any help will be appreciated.

Thanks!

mnawij
Title: Re: import image max resolution
Post by: a.l.e on April 01, 2019, 10:30:11 am
... for the current document, you have to change the "file > document settings"...

"file > preferences" is for all future documents (except for settings that do not depend on the document).

it might be just this...
Title: Re: import image max resolution
Post by: a.l.e on April 01, 2019, 10:31:37 am
this having been said: what kind of document needs 4800 dpi?

... just curious...
Title: Re: import image max resolution
Post by: mnawij on April 01, 2019, 04:16:07 pm
Thanks a.l.e.,

My vendors newest RIP can rasterized to 6000 dpi, might as well take advantage :-) especially in black/white bitmap scans.

Cheers!

mnawij
Title: Re: import image max resolution
Post by: Nermander on April 02, 2019, 06:29:15 pm
But raster DPI is not the same as image PPI, is it?

Generally one image pixel is rasterized into several raster dots.

An at normal viewing distance I doubt you will see a difference between 1200 PPI and 4800 PPI. You would need a magnifying glass to be able to see any difference.
Title: Re: import image max resolution
Post by: mnawij on April 02, 2019, 11:04:06 pm
Nermander, actually no, there is a visual difference with the higher resolution. RIP printing is actually LPI = lines per inch, see this calculator https://www.easycalculation.com/unit-conversion/dpi-to-lpi-converter.php.  It is just easier to talk to the customers in terms of DPI, something they understand.  Most RIPs until within the last decade did a maximum lpi of 200 which converts to 400 dpi, before this the maximum was 150 lpi which equated to 300 dpi (see https://en.wikipedia.org/wiki/Lines_per_inch), this is why most printers recommend a minimum of 300dpi but if they have a new RIP, then they should be requesting higher dpi resolution.  The only drawbacks to the higher lpi/dpi is process time when imaging the film or direct to plate and it theoretically will burn out the imaging laser faster so some shops still run the output at 150-175 lpi which as you mentioned still looks fairly sharp.  Hope maybe this clears it up.  So it does not hurt to ask what lpi your printer is using and adjusting images accordingly...

Cheers!

mnawij
Title: Re: import image max resolution
Post by: Nermander on April 03, 2019, 10:51:40 pm
LPI is as far as I know only used for half-tone rasterization. For other types of rasterization DPI is more often used.

In the past almost all RIPs used half-tone rasters, today there are a lot of rasterization methods.

This page contains an image illustrating this fairly well.
https://aiganhvt.wordpress.com/2009/01/23/understanding-dpi/

And if you scroll down to the DPI section of this page there is another good image (showing square pixels made up of tiny dots).
https://99designs.com/blog/tips/ppi-vs-dpi-whats-the-difference/
Title: Re: import image max resolution
Post by: mnawij on April 04, 2019, 07:58:16 pm
"All you can do is recommend your client to a professional print shop and have the shop, which will know the specifications of its machines, take over from there." This is the very last line in the article, all of the information in the article is for desktop printers, not for high end RIPs which is what is at most print shops.  LPI is still what matters for these... now digital presses are completely different than offset presses in this regard, the articles you shared would be correct in that instance.

Regards,

mnawij