btw i am in paris and i think i own 6 spectros :)
On Monday, December 17, 2018, edmund ronald <edmundronald@xxxxxxxxx> wrote:
The real problem with profile verification with a device is that you are
using the same device as used to measure the patches.
But wait, maybe you have some eys, too.
If you have eyes and a fairly decent instrument, you can usually do closed
loop color managemet and match your print to your screen. Serious
measurement is only really necessary if you are sending files to a third
party.
There are zillions of used spectros on ebay if you really want a different
one.
Edmund
On Monday, December 17, 2018, Yves Gauvreau <gauvreau-yves@xxxxxxxxxxx>
wrote:
I have an I1Studio and I know full well there is nothing I can do to make
it something else and I wouldn't even try, I know it's a waste of time. I
was thinking more of as you said, just improving the reliability and
repeatability and of course the confidence interval as one average more
samples. I recall number like 30 and 40 samples, maybe 90 and 95% C.I. I'm
not sure but that many sample may not be necessary anyway.
My main goal is to be able to make an as excellent profile as possible
with my instrument for maybe a dozen papers at least for now. I'm an old
guy, I speak french mostly, my memory is like Swiss cheese so sometime I
have a hard time understanding your explanations in the docs. I'm also
making conscious effort to minimize waste as much as possible.
1. If possible and useful I'd like to first verify an existing
profile, I just hope it can be done with minimum waste. Something like was
suggested before by Alan maybe sufficient, I don't know, is it?
2. I'd like to learn more on what constitute an excellent profile and
if possible improve on existing one as was also suggested by Alan, again
maybe it's both a waste of time and paper, I don't know, is it?
3. May be I should just forget all the above and find an intelligent
way of selecting an optimal number of patches with the goal of creating an
excellent profile. In the long run it may be the least wasteful approach.
I
say this because I use GamutVision to visualize the gamut of some profile
and more and I often see "hole" in the gamut and other bad behavior and
I'm
not convinced such profile can be improved, again, I don't know.
If someone can explain how the I1Studio software can produce a useful
profile with so few patches? I know they offer this optimize thing based on
image color to "improve" the profile and after a while and a good sample of
various images one may end up with an excellent profile. So why not start
from a large enough set of patches and make an excellent profile from the
start? They want us to think this approach is less wasteful while in fact
it takes more sample and more paper in the end.
I don't pretend to be an expert on the subject of statistical
distribution and I managed to figure out the even distribution was what I
call a uniform distribution but the others ones.
*Optimized Farthest Point Sampling*
*Incremental Far Point Distribution algorithm*, I think the key word
here is algorithm, so it's not a statistical distribution per say, just
a mean to spread the test point as far as possible from each other, right?.
*a quasi-random, space filling distribution both in perceptual and device
space*
*a body centered cubic distribution **both in perceptual and device
space*
Would I be right in thinking the other "distribution" are also more a
kind of "algorithm" as well? Is there any documentation on those
somewhere I can read so I can understand what they do and how?
You also mention the full spread test patch algorithm, would this the
brute force approach I was talking about above?
Would there be better suited algorithm to use with an existing profile
and how to determine the number of total patches and or the number of
neutrals is there any guide lines for this?
For example, I have a Canon Pro 100, only 8 inks, so would it be helpful
to add a certain number of patches for each ink?
All this is very nice but the printer driver have a roll in all this as
well, I guess one wouldn't use a setting for a glossy paper when trying to
make a profile for mate paper and vice-versa. It's obvious it would require
a lot of paper to find the optimal setting for each paper. One of the
reason to start from an existing profile but again it doesn't mean they
went through all the possible setting. I ask all these question mainly
because I don't want to spent a fortune on papers and inks and through most
if not all of this to waste.
Another problem I observed for some paper profile, they have only one
rendering intent that seem to do something useful. So in such case, would
it be possible to fix and improve such profile?
Sorry for all the question.
Thanks,
YG
On 12/16/2018 5:30 PM, Graeme Gill wrote:
Yves Gauvreau wrote:
Hi,
Since my instrument is not top of the line (I1Studio) I thought of making
multiple reading
and use Argyll "average" to remove outliers as much as possible before
further processing,
any suggestion on this as well, I like the median approach but which one?
the primary differences between something like the i1Pro and the i1Studio is
not
the reliability or repeatablity of the measurement process.
(In fact the i1Studio has higher repeatablility than the i1Pro, due to the
use
of a more stable LED light source.) So making multiple measurements and
combining
them is not likely to be something that somehow makes the i1Studio more like
an i1Pro.
You may find benefit in doing this, but it would be to address the
repeatability and reliability of the measurement process, not something
that will have any influence on absolute accuracy.
Cheers,
Graeme Gill.
