Re: Image sizes and resolutions
Re: Image sizes and resolutions
- Subject: Re: Image sizes and resolutions
- From: "Stephen Marsh" <email@hidden>
- Date: Tue, 23 Apr 2002 22:16:56 +1000
Gary, this free sample chapter may be of interest - and the printed versions
does show the differences between the resolution vs image content when
output (the pdf compression/resolution does not show this):
http://www.ledet.com/margulis/PP6_Chapter14.pdf
As for the layout scaling issue - most RIPs do not have a problem, but in a
high volume setting such as newsprint, less RIP time may be critical. These
operations often use JPEG EPS in their workflow, so things are not too bad.
Capturing the required amount of pixels for the image at hand is the best
option - in print terms this would be an image placed at 100%, but +/-20%
seems safe.
Scaling an image down to 10% or other cases where it is being reproduced
significantly smaller is not a good idea in layout, as RIP results can be
unexpected. I have seen problem images which were fixed by
resampling/sharpening a dupe down to 10% rather than just doing it in
layout. Obviously having the original acquired at the correct size would be
even better than resampling down, but on newsprint it is probably not going
to show anyway.
The general choice of separation set-up in Photoshop would be the custom
built in fantasy 'SWOP Newsprint', with the standard 30% or higher dot gain
(perhaps play with custom curves or separate gain) - with a max black of
70-85% and 220-240% TIL depending on things. Ideally you would choose
UCR/GCR black generation/dot gain based on the image content and page
content, but if you need one setting for all situations then medium GCR
would seem the ticket (newsprint often requires intelligent separation and
edits in my experience).
Then selective colour would be used to clean up the separation and endpoints
may even be blown out to try to squeeze a little more contrast out of the
poor situation.
'Proper' profiles for newsprint do not seem to be that common, so the good
old flexible sep table custom CMYK profiles of Photoshop 6 or higher are
still good for this task - but I find it is more what you do with post
separation edits than how you convert. CMYK is often too subjective for a
separation algorithm and newsprint has an even smaller gamut than poor old
common coated web/flatsheet.
Dot gain is the biggest 'colour' problem, if your separations are 'clean' -
my biggest complaint about newsprint results is registration, it would be
nice if every plate was in register, but I understand the process and do not
hold my breath. I do not do a lot of newsprint work anymore - and I am much
happier for it! <g>
Hope this helps,
Stephen Marsh.
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