Re: About Averaging
Re: About Averaging
- Subject: Re: About Averaging
- From: edmund ronald <email@hidden>
- Date: Mon, 23 May 2011 14:54:52 +0200
It's impossible to dispute such a carefully backgrounded analysis.
In particular his explanation indicates that multiple identical sheets
printed in the same location won't help much, since the prints and
measurements on every sheet will probably be impacted by exactly the same
local phenomena eg. head thermals and measurement instrument
perturbations. What could be exceptionally serious would be a contaminated
white-square measurement.
A cheap way to improve your profile by averaging is probably to print at
least 4 rotated scrambled versions of your target in different places on the
sheet, and average the measurements of those sheets.
Edmund
On Mon, May 23, 2011 at 2:28 PM, Marc Levine <email@hidden> wrote:
> Ernst (et al),
> I wanted to point out a key point about averaging: it’s more about
> capturing variability in the print than in the instrument. If a printer was
> “perfect” you would really only need to collect 1 measurement per color
> patch. However, printers are not perfect. They make color by applying some
> kind of liquid, paste or powdered colorant, that is either shot out of a
> nozzle that is flying across a motorized rail, or is dribbled through a maze
> of rollers, or squeezed through a screen, or absorbed into a metal honeycomb
> and then transferred onto a plate, which is then transferred onto a
> substrate. Without even getting in either the variability related to curing,
> or the substrate consistency, speed, and transport alignment, you probably
> get the point that it’s not easy to print the same exact color twice, no
> matter what the technology (some more challenging than others).
>
> Even aqueous inkjet, which is now very mature and very repeatable, will
> demonstrate some variation. In my experience, variation is less likely to
> appear in adjacent dots of ink (where the same ink heads for the same inks
> are on or off). Variation is more noticeable when the inkjet heads need to
> stop, and then print again, somewhere else, on a different part of the
> media, or on a different piece of media. By printing/measuring/averaging 2
> (or more) sheets, you are collecting data that better illustrates that
> variability of your process. Do you need absolutely need to average multiple
> samples? Of course not. Especially n the case of inkjet, the difference
> might be futile. That being said, for proofing at least, it’s all about the
> futile differences and averaging might get you an extra .1 or .15 dE.
>
> So, in response to your comment (reworded) "is the multi-sampling that
> instruments do a reasonable replacement for averaging multiple sheets?”....
> I would say no. While it does help the instrument getter a better picture of
> the patch your measuring (and help it pick out one patch from another).
> Averaging multiple sheets is more about capturing the variation between that
> patch and the next time or place that it is printed.
>
> Marc
>
>
> On May 22, 2011, at 3:03 PM, email@hiddenote:
>
> > Send Colorsync-users mailing list submissions to
> > email@hidden
> >
> > To subscribe or unsubscribe via the World Wide Web, visit
> > http://lists.apple.com/mailman/listinfo/colorsync-users
> > or, via email, send a message with subject or body 'help' to
> > email@hidden
> >
> > You can reach the person managing the list at
> > email@hidden
> >
> > When replying, please edit your Subject line so it is more specific
> > than "Re: Contents of Colorsync-users digest..."
> >
> >
> > Today's Topics:
> >
> > 1. Re: iSis was Re: Any comments or feedback on i!Publish? (Lou
> > Dina) (Ernst Dinkla)
> > 2. Re: iSis was Re: Any comments or feedback on i!Publish? (Lou
> > Dina) (dpascale)
> >
> >
> > ----------------------------------------------------------------------
> >
> > Message: 1
> > Date: Sun, 22 May 2011 14:07:19 +0200
> > From: Ernst Dinkla <email@hidden>
> > Subject: Re: iSis was Re: Any comments or feedback on i!Publish? (Lou
> > Dina)
> > To: "email@hidden >> ColorSync Users Mailing List"
> > <email@hidden>
> > Message-ID: <email@hidden>
> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed
> >
> >
> > On 05/18/2011 09:22 PM, Tyler Boley wrote:
> >> regarding the iSis, I'm finding with inkjet coated fine art papers, the
> >> usual suspects, that the rubber drive washers pick up (well dried) black
> >> ink from the black start bar and proceed to put it down in slight
> >> amounts on the lower color patches. With very light colors this clearly
> >> taints the result, with repeated measurement for averaging it's clearly
> >> seen, the later measurements differing from the 1st, progressively
> >> worse. Anyone find this problematic? I doubt my averaged data is more
> >> reliable than the first pass in the light patches.
> >> This leads me to my second question. If these instruments make multiple
> >> samples per patch and average them on the fly, other than some gross
> >> alignment error what is the point of multiple chart measurement for
> >> averaging if there has been significant averaging with one pass anyway?
> >> Tyler
> >
> > I thought that the HP Z spectrometer design was based on the iSis in
> > some aspects. In calibration just after printing the targets the Z
> > models will start with scanning the last printed patches first. So no
> > patch is touched by a pinch roller before being measured. The pinch
> > rollers of paper transport do not affect the print surface either but
> > when I observed that reversed scan order first I thought someone paid
> > attention to that aspect too.
> >
> > Averaging within one patch helps already but given the trend to increase
> > patch numbers and related to that smaller patch sizes I wonder whether
> > that is enough. It does not compensate on spectrometer temperature
> > deviations, not on differences in printing directions or paper texture
> > directions (HM Sugarcane), not on hysterises in spectrometers etc. In
> > strip readings the boundary detection takes its toll too.
> >
> > For quite simple custom greyscale targets to be measured on a HP Z3200,
> > 17 patches for linearising it, I made a descending and ascending range
> > twice. Large patches anyway on that machine and the spectrometer keeps
> > some distance from the patches. I wonder sometimes whether random
> > distribution of patches actually dampens spectrometer hysterises if
> > there is not extra check in the distribution of the patches on that
> issue.
> > A target print page + patch distribution that can be scanned in two
> > directions would be an improvement to reduce more effects.
> >
> > If more sampling is done it would be nice to throw the two most extreme
> > readings in the bin and average the remaining ones, more samples usually
> > increases the spread of the results too.
> >
> > --
> > Met vriendelijke groeten, Ernst
> >
> > Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/
> >
> > | Dinkla Grafische Techniek |
> > | www.pigment-print.com |
> > | ( unvollendet ) |
> >
> >
> >
> > ------------------------------
> >
> > Message: 2
> > Date: Sun, 22 May 2011 11:35:34 -0400
> > From: dpascale <email@hidden>
> > Subject: Re: iSis was Re: Any comments or feedback on i!Publish? (Lou
> > Dina)
> > To: Ernst Dinkla <email@hidden>,
> > email@hidden
> > Message-ID: <5054DCE3A5634391AFB6DE8FEE8FB7EA@noel2003>
> > Content-Type: text/plain; format=flowed; charset=iso-8859-1;
> > reply-type=response
> >
> > Hello Ernst,
> >
> >> If more sampling is done it would be nice to throw the two most extreme
> >> readings in the bin and average the remaining ones, more samples usually
> >> increases the spread of the results too.
> >>
> >
> > This is where a "weighted average", such as done in MeasureTool and
> > PatchTool, can help.
> > For at least 3 readings, and somewhere less than 20, a weighted average
> > first takes the standard average and then recomputes the average based on
> > each reading vs the standard average. The farther a reading is from the
> > average, the less it is considered in the average. The effect of
> "oddball"
> > readings is thus minimized. As you increase the number of readings, the
> > weighted average tends to be equal to the standard average. The effect is
> > most beneficial when doing averages on less than 10 series of measures.
> At
> > 15-20 readings there is usually no practical differences. In my view,
> > because of the time required to get all the data, an average made on
> between
> > 3 and 5 series of measurements is optimal.
> >
> > Danny
> >
> > www.babelcolor.com
> >
> >
> > ----- Original Message -----
> > From: "Ernst Dinkla" <email@hidden>
> > To: <email@hidden>
> > Sent: Sunday, May 22, 2011 8:07 AM
> > Subject: Re: iSis was Re: Any comments or feedback on i!Publish? (Lou
> Dina)
> >
> >
> >>
> >> On 05/18/2011 09:22 PM, Tyler Boley wrote:
> >>> regarding the iSis, I'm finding with inkjet coated fine art papers, the
> >>> usual suspects, that the rubber drive washers pick up (well dried)
> black
> >>> ink from the black start bar and proceed to put it down in slight
> >>> amounts on the lower color patches. With very light colors this clearly
> >>> taints the result, with repeated measurement for averaging it's clearly
> >>> seen, the later measurements differing from the 1st, progressively
> >>> worse. Anyone find this problematic? I doubt my averaged data is more
> >>> reliable than the first pass in the light patches.
> >>> This leads me to my second question. If these instruments make multiple
> >>> samples per patch and average them on the fly, other than some gross
> >>> alignment error what is the point of multiple chart measurement for
> >>> averaging if there has been significant averaging with one pass anyway?
> >>> Tyler
> >>
> >> I thought that the HP Z spectrometer design was based on the iSis in
> >> some aspects. In calibration just after printing the targets the Z
> >> models will start with scanning the last printed patches first. So no
> >> patch is touched by a pinch roller before being measured. The pinch
> >> rollers of paper transport do not affect the print surface either but
> >> when I observed that reversed scan order first I thought someone paid
> >> attention to that aspect too.
> >>
> >> Averaging within one patch helps already but given the trend to increase
> >> patch numbers and related to that smaller patch sizes I wonder whether
> >> that is enough. It does not compensate on spectrometer temperature
> >> deviations, not on differences in printing directions or paper texture
> >> directions (HM Sugarcane), not on hysterises in spectrometers etc. In
> >> strip readings the boundary detection takes its toll too.
> >>
> >> For quite simple custom greyscale targets to be measured on a HP Z3200,
> >> 17 patches for linearising it, I made a descending and ascending range
> >> twice. Large patches anyway on that machine and the spectrometer keeps
> >> some distance from the patches. I wonder sometimes whether random
> >> distribution of patches actually dampens spectrometer hysterises if
> >> there is not extra check in the distribution of the patches on that
> issue.
> >> A target print page + patch distribution that can be scanned in two
> >> directions would be an improvement to reduce more effects.
> >>
> >> If more sampling is done it would be nice to throw the two most extreme
> >> readings in the bin and average the remaining ones, more samples usually
> >> increases the spread of the results too.
> >>
> >> --
> >> Met vriendelijke groeten, Ernst
> >>
> >> Try: http://tech.groups.yahoo.com/group/Wide_Inkjet_Printers/
> >>
> >> | Dinkla Grafische Techniek |
> >> | www.pigment-print.com |
> >> | ( unvollendet ) |
> >>
> >
> >
> >
> > ------------------------------
> >
> > _______________________________________________
> > Colorsync-users mailing list
> > email@hidden
> > http://lists.apple.com/mailman/listinfo/colorsync-users
> >
> > End of Colorsync-users Digest, Vol 8, Issue 131
> > ***********************************************
>
> _______________________________________________
> 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
>
_______________________________________________
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