Re: Grainy Laser Profiles
Re: Grainy Laser Profiles
- Subject: Re: Grainy Laser Profiles
- From: Graeme Gill <email@hidden>
- Date: Tue, 27 Jun 2006 22:21:17 +1000
Karsten Krüger wrote:
This can not be generalized. It highly depends on the printing
technology and the paper being used.
The "noise" comes from uneven electrostatic behaviour of the paper.
When mixing colors directly on the paper (used by older technologies)
the paper has a strong influence. Only specially treated paper will
give decent results (i.e. ColorCopy/Colotech brands). In this case
reducing CMY and adding K will lead to better results.
Modern printers use indirect printing. They have a "digital web" which
accumulates all ink, and have a one step transfer to the paper. The
quality related electrostatic process ist between the drumm(s) and the
web, which does not have issues like paper. The quality of the paper
has only little influence, allmost any type of paper (coated, uncoated,
recycling) can be used. It just has to be heat resistant for the fuser.
It may well be that such technology is sometimes better, but I've
got to say that none of the transfer belt technology engines has
impressed me that much in terms of printing quality. When in good
shape, the very best prints I've seen have been out of direct
transfer engines, ie. the Canon 1180 and Xerox 1250, which we used
extensively for proofing. Transfer belts may well be lower maintenance,
and perhaps degrade more slowly than direct transfer technology.
None of this alters the basic physics that black has a higher
visual contrast than C, M or Y, hence a high black puts a lot of
faith in the black channel being free of any visual artefacts,
whereas dividing the neutral component amongst C, M, Y and K,
leads to a wider allowance for deterioration in the print engine behaviour.
An other aspect is the raster being used. There are 2 types: line and
dot. Line raster usually addresses about 600dpi and has halftoning
(theoretically 256 steps of ink on the paper), while dot uses the same
process like offset (collecting dots into a haltone cell). Line raster
usually gives more details in pictures and small text, but showing
stronger noise in areas of solid colors. Dot raster is not as sharp and
detailed as line raster, but has smooth solid colors without noise.
Line raster has an other issue - depending on the print engine colors
like to shift during production, especially in highlights (less than
20% of ink).
If a printer is able to produce more than 1200 dpi, dot raster is the
better choice in most cases.
And I've never been impressed with the numbers game race to "higher" resolution.
400 DPI "photo" contone gave excellent, low noise prints. The replacement 600 DPI
machines all had noticeable screening artefacts, and seemed more subject
to noise artefacts, while consuming 2.25 times the memory and bandwidth.
With line raster less CMY and more K usually gives better results. With
dot raster at least the printers I know (high end Xerox) behave allmost
like an offset press - any real world (=offset) GCR/UCR settings will
work fine.
When it's in good condition, yes. But run a few thousand prints, and
you're black channel won't be looking so clean.
Graeme Gill.
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden