QTR-Quadtone RIP

I have made a suggestion to Mike Chaney (author of Profile Prism) that 
he could extend PP to be able to measure 21 or 100 step grey scale 
wedges produced from QTR calibration mode to generate the limearization 
curves.  I believe this would be quite simple to de.  It won't be as 
accurate as using a proper desimete, but better than nothing.

Anyone think this would be a ggod idea - would you buy PP if it were 
extended to do this?

Keith

--- In QuadtoneRIP@yahoogroups.com, "keith_r_smith_99" <keith@k...> wrote:
>
> I have made a suggestion to Mike Chaney (author of Profile Prism) that 
> he could extend PP to be able to measure 21 or 100 step grey scale 
> wedges produced from QTR calibration mode to generate the limearization 
> curves.  I believe this would be quite simple to de.  It won't be as 
> accurate as using a proper desimete, but better than nothing.
> 
> Anyone think this would be a ggod idea - would you buy PP if it were 
> extended to do this?

No.

PP is a scanner based color printer profiling system, and even the
best of those is not worth bothering with. Tacking other functionality
on top of a program that is not useful to begin with is a waste of
time and money. If I were not capable of writing a tool to measure
grayscale densities using a scanner, I would consider buying a lower
priced tool intended specifically for that purpose. But not something
carrying color profiling baggage.

My experience with PP is not the same as yours. Yes of course there
are limitations using ascanner based profile, but you need to put it
in perspective with the cost vs a 'proper' system like the Eye1.

Have you used PP? - I have achieved results surprizingly close to
those I have had custom made for me. 

I do agree that for QTR B&W work, you are better looking at alternate
hardware, I picked up a Macbeth 940 for $90 which despite being 20
years old works fine, the color filters have likely faded, however for
B&W work this does not matter. You can find similar units on ebay for
even less than this,

Regards

> 
> No.
> 
> PP is a scanner based color printer profiling system, and even the
> best of those is not worth bothering with. Tacking other functionality
> on top of a program that is not useful to begin with is a waste of
> time and money. If I were not capable of writing a tool to measure
> grayscale densities using a scanner, I would consider buying a lower
> priced tool intended specifically for that purpose. But not something
> carrying color profiling baggage.
>

I guess it wouldn t be a bad idea for folks who don t have a densitometer. I bet the big question would be if Mike Chaney would do it.  He hasn t been very

>> I have made a suggestion to Mike Chaney (author of Profile Prism)  
>> that
>> he could extend PP to be able to measure 21 or 100 step grey scale
>> wedges produced from QTR calibration mode to generate the  
>> limearization
>> curves.  I believe this would be quite simple to de.  It won't be as
>> accurate as using a proper desimete, but better than nothing.
>>
>> Anyone think this would be a ggod idea - would you buy PP if it were
>> extended to do this?
>
> No.
>
> PP is a scanner based color printer profiling system, and even the
> best of those is not worth bothering with.

Can you explain *why* this is so? The basic approach of PP *appears*  
to me to be sound: print a defined or known source file with no  
printer corrections at all, scan it at the same time as a target of  
known colours and densities, once again with no corrections at all,  
and then create a profile based on comparing the printed target with  
the standard target. The resulting profiles are unique to the  
equipment, of course, but why would they be inherently faulty?  [I  
just bought PP!!]

> ... If I were not capable of writing a tool to measure
> grayscale densities using a scanner, I would consider buying a lower
> priced tool intended specifically for that purpose. But not something
> carrying color profiling baggage.

Can you suggest such a "tool to measure grayscale densities using a  
scanner" for those of us who have insufficient time or talent to do  
it for ourselves. Is there anything out there you would recommend?  
Most of us have scanners, and a decent "software densitometer" would  
be helpful.

Myron

I have an X-Rite 810 that I bought off Ebay. I paid about $150 for it about
a year ago. That included several alignment step tablets. They may be
cheaper today.

I also have an Epson 2400 scanner and a Fauste IT-8 calibration chart. With
Vuescan I can calibrate the scanner using the IT-8 chart.

I have tried making curves with the scanner and using the densitometer.
Aside from the convenience of being able to import density values directly
into a spreadsheet from the densitometer (important if you do a lot and
value your time), the scanner seems to lack precision near the ends of the
greyscale. The dark patches in particular don't measure the same when
measured with the scanner as they do when measure with the densitometer. 

Perhaps I didn't work at it enough. I know Paul Roark's web site (see the
BlackandWhitethePrint list) has a procedure for "calibrating" your scanner
that might be applicable to those using one to build QTR curves.

The possible benefits that Profile Prism might provide would be
1.	better calibration of the scanner
2.	automation of entry of step density values into a file in a form
usable by QTR

As a densitometer, the X-Rite 810 only measures the L axis. It doesn't
provide any useful a and b axis information (in Lab terms). Using PP might
be a cheap way to get tone information into ICC profiles created by QTR - as
opposed to the Eye-1 at $800.

Tom Moore

I have several densitometers but they were in storage 1000mi. away at
the time I tried QTR out. Being the impatient sort,I used an epson
3170 and an IT8 chart to build the curves for a self mixed Quad set on
a 3000. It worked very well indeed. Scan the IT8 or any other
calibrated step scale along with your test scales.In photoshop, adjust
levels to match Lab L* on the 22nd(not the very darkest) and min
patches of the IT8. Then just read off the Lab L* values for your QTR
patches using the eyedropper tool or dragging the curser over them.
Yes,you may need to do a slight bit of fudging in the darkest values
if your paper/ink combination just happens to have a great d'max
capability, as mentioned below.Photoshop only shows 1% intervals for
Lab L* so high densitys can be very close or the same reading.You can
get around that by switching to rgb mode and looking at the patches to
see a bit more separation to determine which is darker. Then just
nudge your L* figure on that patch a bit lower and use it as input to
QTR for the linearisation.The same thing is true for the lightest
patches(generaly only the last 2) where it is little problem. If they
both read something like 99 L*, just call the last one maybe 99.1 L*
and go. Just be certain you don't give QTR any two readings that are
identical and you will be fine. Once you have generated the
linearisation curve, use it to reprint the scale. If it looks good and
shows reasonable separation of all patches it is quite useable to make
excellent prints. 

Having said all this, I want to make clear to all and sundry, that I
am not calling it a better or just as good way to generate the curves.
I am simply saying it is very doable and works. When I did get around
to dragging out one of my instruments this fall I took the readings
below from the linearised QTR stepscale.They tell me, to my own
satisfaction, that the above method didn't do a bad job.

Regards
Duane

VMCOOL 21STEP PREM DUOBRITE
 
 #   CIE-X  CIE-Y  CIE-Z   L*     a*     b*     dVIS' dRED' dGRN' dBLU'   
 
 1   1.310  1.211  1.219 10.637    4.49    -3.14 1.917 1.920 1.917 1.812  
 2   1.912  1.791  1.773 14.348    4.55    -3.27 1.747 1.717 1.753 1.651  
 3   2.562  2.457  2.372 17.724    3.84    -3.12 1.610 1.582 1.618 1.522  
 4   3.841  3.522  3.396 22.025    6.87    -3.48 1.454 1.410 1.455 1.375  
 5   5.387  5.103  4.782 27.025    5.71    -3.21 1.293 1.254 1.294 1.225  
 6   7.262  6.874  6.291 31.519    6.34    -2.87 1.163 1.126 1.159
1.109   
 7   9.167  8.856  7.931 35.706    5.35    -2.46 1.053 1.021 1.053
1.010   
 8  11.347 11.193  9.842 39.903    4.08    -2.06 0.952 0.929 0.951
0.920   
 9  14.671 14.518 12.559 44.967    4.16    -1.66 0.839 0.817 0.840
0.814   
10  18.311 18.366 15.673 49.937    3.21    -1.27 0.736 0.716 0.738
0.722   
11  21.736 21.838 18.560 53.854    3.23    -1.18 0.661 0.646 0.665 0.646 
12  25.361 25.590 21.716 57.646    2.94    -1.18 0.592 0.575 0.594
0.575   
13  29.113 29.294 25.069 61.040    3.39    -1.61 0.534 0.515 0.534
0.517   
14  33.145 33.079 28.488 64.225    4.49    -1.98 0.481 0.463 0.479
0.464   
15  38.691 38.771 33.089 68.585    4.23    -1.64 0.412 0.396 0.414
0.402   
16  44.043 44.253 38.264 72.397    4.08    -2.39 0.355 0.336 0.359
0.341   
17  47.960 48.784 41.697 75.317    2.58    -1.85 0.312 0.299 0.315
0.304   
18  55.113 55.905 47.888 79.559    3.09    -2.06 0.253 0.246 0.255
0.244   
19  62.013 63.700 54.457 83.809    1.41    -2.03 0.196 0.196 0.200
0.190   
20  69.493 70.753 61.323 87.365    2.79    -2.93 0.151 0.149 0.156
0.137   
21  84.687 84.531 72.242 93.681    6.11    -2.21 0.073 0.069 0.074
0.074   





--- In QuadtoneRIP@yahoogroups.com, "Tom Moore" <r.t.moore@r...> wrote:
>
> I have an X-Rite 810 that I bought off Ebay. I paid about $150 for
it about
> a year ago. That included several alignment step tablets. They may be
> cheaper today.
> 
> I also have an Epson 2400 scanner and a Fauste IT-8 calibration
chart. With
> Vuescan I can calibrate the scanner using the IT-8 chart.
> 
> I have tried making curves with the scanner and using the densitometer.
> Aside from the convenience of being able to import density values
directly
> into a spreadsheet from the densitometer (important if you do a lot and
> value your time), the scanner seems to lack precision near the ends
of the
> greyscale. The dark patches in particular don't measure the same when
> measured with the scanner as they do when measure with the
densitometer. 
> 
> Perhaps I didn't work at it enough. I know Paul Roark's web site
(see the
> BlackandWhitethePrint list) has a procedure for "calibrating" your
scanner
> that might be applicable to those using one to build QTR curves.
> 
> The possible benefits that Profile Prism might provide would be
> 1.	better calibration of the scanner
> 2.	automation of entry of step density values into a file in a form
> usable by QTR
> 
> As a densitometer, the X-Rite 810 only measures the L axis. It doesn't
> provide any useful a and b axis information (in Lab terms). Using PP
might
> be a cheap way to get tone information into ICC profiles created by
QTR - as

> opposed to the Eye-1 at $800.
> 
> Tom Moore
>

--- In QuadtoneRIP@yahoogroups.com, MGochnauer <goch@u...> wrote:
>
> > PP is a scanner based color printer profiling system, and even the
> > best of those is not worth bothering with.
> 
> Can you explain *why* this is so? The basic approach of PP *appears*  
> to me to be sound: print a defined or known source file with no  
> printer corrections at all, scan it at the same time as a target of  
> known colours and densities, once again with no corrections at all,  
> and then create a profile based on comparing the printed target with  
> the standard target.

Because of something called "observer metamerism". You're probably
familiar with "illuminant metamerism", where a color appears different
under different lights. (more properly, two colors that appear the
same under one light appeaer different under another).

The opposite of that is "observer metamerism". Two colors that appear
to be identical to one observer appear to be quite different to
another observer. Now, imagine one of those observers is your eye, and
the other is your scanner. They're nowhere near close in color
perception: two colors that look identical to your eye may look very
different to the scanner, and two colors that look identical to the
scanner may look very different to your eye. So, if you create a
profile with the scanner, and it works out all the math to make the
colors on the patch you printed out look identical to the patches in
the reference card that came with Profile Prism, you can still have a
very wrong profile, because the colors that look identical to the
scanner look totally different to your eye.

The reason why spectrophotometers such as the eye-one break color up
into 16 or 31 different bands, then do a whole bunch of math on those
bands, is to get color numbers that match the characteristics of a
human eye, so there will be no observer metamerism.

Now, it's possible to get lucky with a scanner based solution, and
it's possible to tweek it until it works well under a relatively small
set of conditions. i.e. if the Profile Prism reference card uses inks
that are similar to a particular printer's ink, then if you calibrate
the printer to match those colors when observed by the scanner, they
will look similar when observed by the eye. But any ink that deviates
from that match will make a poor profile. Or any paper that differs
from the paper used in the reference, as far as fluorescence (OBAs,
optical brightening addatives) will also cause a poor profile.

> The resulting profiles are unique to the  
> equipment, of course, but why would they be inherently faulty?  [I  
> just bought PP!!]

Are you getting results that you like? That's the big issue. There's
two kinds of profiles, just like there's two kinds of color:
"accurate" and "pretty". A scanner based profiler can make a "pretty"
profile. It can fix problems with shadow details blocking up, or color
crossovers. It may leave you with a profile where all grays, whether
light or dark, are too magenta, but it shouldn't leave you with one
where light grays are green, while dark grays are magenta.

If your income depends on the client seeing that you've accuratly
duplicated the color of their corporate logo, or the model being
satisfied that you've got her makeup color right, or the bride being
happy about the color of her dress, "pretty" profiles don't cut it,
and you end up in the world of "accurate" profiles.

> > ... If I were not capable of writing a tool to measure
> > grayscale densities using a scanner, I would consider buying a lower
> > priced tool intended specifically for that purpose. But not something
> > carrying color profiling baggage.
> 
> Can you suggest such a "tool to measure grayscale densities using a  
> scanner" for those of us who have insufficient time or talent to do  
> it for ourselves. Is there anything out there you would recommend?  
> Most of us have scanners, and a decent "software densitometer" would  
> be helpful.

There is one, and I'm having the devil of a time remember ing the
name. I want to say VueScan, but that doesn't feel right. I do recall
that it did need periodic calibration with a reference chart that had
several known density squares. Not too hard to make.