[Scribus] grayscale images imported as RGB?

jon info
Wed Mar 14 11:28:31 CET 2007


Hi Terence,

grayscale printing to (non proofing) inkjet, thermotransfer or  
laserprinters depends on custom printerdrivers wich will convert  
colors to printer-suitable spaces.
Most inkjets will support neutral (grayscale) blacks with cyan (or  
sth equal), and as far as I know most of them will convert any color  
to RGB first - even if your printer supports cmyk or 6 to 8 (cmyk+)  
colors.
Colorspace does matter here as long your printerdriver is able to  
recognize it but, as far as I know, most don't?

Proofers are different because they are designed to output profiled  
prints and more or less direct cmyk.
Are these profiles the profiles of the printing machine (paper/ 
printcolors) you will print on? Does the printshop calibrate there  
machines to THIS profile?
And proofers put out ideal print under ideal circumstances not "real  
life" mass printing (staying simple here :)

OK, the need (?) of neutrality? Print is, under common conditions,  
profiled or not, tolerant.
(with a few exceptions) - you always will have a tolerance of around  
(or at least of) 5 % in dot sizes.
Say if you have sth neutral (wich is isn't?) 40-40-40-0 you might get  
(depend on printing color, paper, temperature, mood, water, etc)
sth like 45-40-45-0 known as sth green within the first 2500 prints -  
and if the printer is in a bad mood (or is trying to recalibrate her  
machine), from 2500 to 5000 you will get 40-40-50-0, from 5000-7500  
sth like ... so - you will have no guarantee for neutrality.

Another reason to use only K for grayscale images is the raster dots.  
4 color standard (not modulated) raster dots are created to form  
circles and will always produce slightly visible moir?s. Though  
"more" information is provided gray produced out of 3-4 colors seem  
to be slightly less sharp as if created with only "pure" K (very much  
depending on raster dot size).

One disadvantage using exclusively K is the lack of deep black and  
therefore contrast.

To compensate both disadvantages (lack of neutrality, moir?, lack of  
contrast) one common way is to support "neutral" colors with a lower  
percentage of CMY.
Say if you want a "neutral" (slightly cyan - which is intended to be  
recognized as neutral) 90 percent tone you might generate sth like  
20-10-10-80 - wich has
enough "deepness" and some guarantee to not being printed with too  
much visible tolerance or too much visible moir?.


> You're going to save expensive color pigments (toner/ink).  
> Depending on your
> printer, the print job can be done in one pass instead of 4 (up to  
> 4 times
> faster). You're sure you won't get any color cast...
>
> In short, your print will be better, faster and cheaper.
>
> 2007/3/13, Terence Chan <terence at onetel.com>:
>>
>> Excuse my ignorance but why is it important/deirable to have  
>> greyscale
>> images on the K plate only? I finished a book recently with lots
>> of greyscale images colour profiled in RGB/CMYK PDF (set to  
>> "printer").
>> The page proofs from the printer look just like what I wanted, so  
>> what's
>> wrong with that?
>>
>> Terence
>>
>> On Tue, 13 Mar 2007, Vladimir Savic wrote:
>>
>> >
>> > Try! And prove you're wrong! Tested with Acrobar Pro from CS  
>> creative
>> suite.
>> > RGB input is not a bad solution at the first place. :) Output is  
>> color
>> > profiled CMYK PDF. (which means that fallowing my procedure,  
>> finally
>> applied
>> > color profile will only effect visual appearance of K plate, but  
>> not
>> it's
>> > nature - it will be grayscale (that is K only), not composite
>> grayscale.)
>> >
>> > BTW, I'm running linux, so I don't have anything other then The  
>> GIMP to
>> work
>> > with. Using PS on win boxes is much faster/natural way to make CMYK
>> images
>> > without that much pain, but never tried it... :(
>> >
>> > Vlada
>> >
>> > > Setting the image to CMYK does work for me. I don't know wich  
>> app you
>> > > use but if you convert
>> > > your image to CMYK you should make sure you delete all data  
>> from the
>> > > CMY channels and copy the original
>> > > K or Grayscale data only to K or try "maximum Black"  
>> conversion mode
>> > > (before you import them)
>> > >
>> > > Jon
>> > >
>> > > Am 12.03.2007 um 12:54 schrieb Vladimir Savic:
>> > > > On Monday 12 March 2007 17:43:36 Terence Chan wrote:
>> > > >> Yes, I believe this is normal behaviour for scribus - why  
>> is this
>> > > >> a problem? So long as you apply the appropriate icc input and
>> output
>> > > >> profiles the greyscale images should appear ok when printed  
>> and on
>> > > >> the screen.
>> > > >>
>> > > >> Terence
>> > > >
>> > > > Hmmm...
>> > > > I was doing something obviously wrong here too (talking about
>> > > > Scribus 1.3.3.x
>> > > > not 1.3.4cvs). "Appropriate profile" is a key point. No  
>> profile can
>> > > > ensure
>> > > > grayscale RGB (picture in RGB color space but completely
>> > > > constructed of r=g=b
>> > > > values pixels) picture to appear on K plate only when PDF gets
>> > > > token to
>> > > > prepress office.
>> > > > Right approach would be to ask of user if imported picture is
>> > > > composite
>> > > > grayscale picture or single color channel image.  
>> Fortunately, in
>> > > > 1.3.4 there
>> > > > is a simple solution: image effects -> apply colorize image and
>> > > > give that
>> > > > picture 'black' color colorization (Don't take further  
>> writing for
>> > > > granted
>> > > > but I think choosing 0%C 0%M 0%Y 100%K "in-Screibus hand made"
>> > > > color doesn't
>> > > > work correctly)
>> > > >
>> > > > Vlada
>> > > >
>> > > >> On Sun, 11 Mar 2007, Lila Pagola wrote:
>> > > >>> hi!
>> > > >>> I'm working with Scribus in a book, almost finished,  
>> because we
>> > > >>> are in
>> > > >>> press with everything except cover.
>> > > >>>
>> > > >>> Preparing the cover design for pre-press (I don't if in  
>> english
>> > > >>> it's said
>> > > >>> that way), I have found a rare behavoir of Scribus with  
>> grayscale
>> > > >>> images:
>> > > >>> they are considered as RGB files, in any format I try to  
>> import
>> them
>> > > >>> (PNG8, gif, tif). And If I import them as CMYK I have  
>> information
>> > > >>> in the
>> > > >>> 4 channels when the image is just black.
>> > > >>>
>> > > >>> Somebody has experiencied something similar? Am I doing  
>> something
>> > > >>> wrong?
>> > > >>> I did a quick search on the web and the list's archives and I
>> > > >>> didn't find
>> > > >>> any report of this problem.
>> > > >>>
>> > > >>> Our project has a wiki when we are uploading the problems and
>> > > >>> solutions
>> > > >>> we found, in spanish, sorry (and for my english sorry too)
>> > > >>> the url is http://nomade.liminar.com.ar/wakka.php?wakka=MaBI
>> > > >>>
>> > > >>> Thanks in advance for any clue ...
>> >
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>> >
>>
>>
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