Re: Gold resolution
Re: Gold resolution
- Subject: Re: Gold resolution
- From: Jim Rich <email@hidden>
- Date: Fri, 08 Mar 2002 08:52:26 -0800
On 3/8/02 3:50 AM, "Adriano Von Markendorf" <email@hidden> wrote:
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Hi folks,
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Greetings from Greatest-beach's-beautiful-people-Land...!
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I'm wondering about a well-knowed subject, I just receive the Bruce Fraser
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book and I read about good rules of image quality and resolution.
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Well, in my country the gold rule always was:
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best dpi = target lpi x 2 in a plane offset.
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eg. if you want 150 lpi target print the best resolution are 150 x 2 = 300
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dpi.
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So, about a year ago I read a extense article in the "Publish" brasilian
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version ( I'm still trying to recover the author or sources!) talking about a
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wasting of time, storage and quality using above rule. In this text the author
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claim that the true scientific rule would be a: lpi x 1,46 / eg. 150 x 1,46 =
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222 dpi and if you use more than that will got a "interpolation" effect that
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create a new color pixel taking the average of excess of pixels. For sure the
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article author give the links and explain in a good way. But, I have a strange
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situation, because in fact, I can't get best results with 300 dpis image than
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222 dpis in my offset 4 colors printers and I look very close the 133 lpi
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samples images from the Bruce book and I CAN see best details using the X 2
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rule.
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Almost forgot ! Our offset system use positive films,the TIL for plane offset
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are 320% using coated couche paper.
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The average dot gain are 50 /64 CMY - 50/69 K.
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Somebody hear about this article?
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Bruce, I missing something?
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How can I made a real "scientific" test to julge the best rule?
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Thank's for any advance,
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Adriano von Markendorf email@hidden
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"I-C-Cm vitamin's inside" Rio de Janeiro - Brazil
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ps:Bruce, congratulations for your book, I really liked your aproach.
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This type of information has been around at least since the late 1980s. If I
understand your question . This scientific rule is based on how you measure
the resolution of pixels vs how you measure the resolution of a halftone
screen. Pixels are measured horizontally and halftone dots are measured on
the diagonal. If I got this mixed up, some please jump in. But none the less
when you do the math to get the ratio of pixels to dots you get less than
the 2 to 1 rule for image resolution. I is something like a 1.33 to 1 ratio
for scanning resoultion. .This scientific formula will work for some images.
We tested it out in the early 1990 and even presented it at Seybold.
Here is the rub. While the math is good it does not work in production well,
because in a lot of cases operators change the file dimension up say 10% to
15% or more. When you do that you ruin the image resolution (and
production), then you have to rescan the image.
This is a classic case of a an intelligent newbee trying to change the rules
of imaging to save disk space but not understanding the complete process.
Jim Rich
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