Re: Averaging multiple cmyk profiles from multiple cmyk target readings
Re: Averaging multiple cmyk profiles from multiple cmyk target readings
- Subject: Re: Averaging multiple cmyk profiles from multiple cmyk target readings
- From: Roger Breton <email@hidden>
- Date: Wed, 27 Jul 2005 16:21:26 -0400
> Please comment on printing muliple cmyk targets for a press, reading and
> creating the multiple pofiles and then averaging them.
David,
There's no question that press profiles can hardly be derived from one
single sheet. Just how many sheets and which sheets is the toughest
question. In my practice, I have aproached it from the point of view of a
statistician. As you know, there are many sampling strategies. I first used
stratified samples but then I reason that this does not represent the true
underlying nature of the process which, IMHO, has a random component to it.
You have to think about how is it that colors vary on a printing press
throughout some pressrun. In large runs, you'll see the pressman adjusting
ink density upwards or downwards but always around some *central* values,
the target or standard. But, in my view, I have not studied this extensively
or rigorously, btw, if nothing major is breaking in a press during the run,
the color will vary randomly and the true measure of the press color will
follow and random variable that is normally distributed around the mean.
That's my theory. So, say in a sample of 500 press sheets, I'll take 30
readings of a random selection and average the results. Now that's the first
part of this process. There is a second part to this? Yes, it's called
"smoothing". And to my knowledge not too many profilers allow you to do
this. Maybe others can correct me here? I'd love to hear it from the
horses's mouth. But in PrintOpen5, there is a function with a scale to
gradually smooth measurements. So, on top of averaging, I also practice
smoothing. But I'm getting away from the subject...
Regards,
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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