Re: iSis was Re: Any comments or feedback on i!Publish? (Lou Dina)
Re: iSis was Re: Any comments or feedback on i!Publish? (Lou Dina)
- Subject: Re: iSis was Re: Any comments or feedback on i!Publish? (Lou Dina)
- From: dpascale <email@hidden>
- Date: Sun, 22 May 2011 11:35:34 -0400
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 ) |
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