Digital BW, The Print

Paul,

Thank you for the very good post about the nature of the RGB separation
curves used with the VM inks and your suggestions on how to make
adjustments. I have added your post to the Files section in folder:

Files > Ink Sets > MIS > MIS Variable Mix

As you and I have discussed, there may be a possibility that a reduced gamut
toner for the VM will require less radical curves in the "mw" and "wm" tonal
ranges. I know you have a ways to go before you finalize your non-warming
toner but can you give us some info on what you have tried so far? Warming
aside, I would like to give the set a try with the reduce gamut toner. Can
you share your recipe for the new toner in the M and M+ position for the hex
printers?

Thanks,
Martin


----- Original Message -----
From: "Paul Roark" <paul.roark@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, June 19, 2002 9:29 AM
Subject: RE: [Digital BW] MIS VM-sepia -- hextone neutral prints


> The vm-sepia inkset uses the same "densities" as the standard MIS-VM
inkset.
> As such, I hoped that the curves that currently existed would be at least
> close.  In fact, you can see the posted scan of the Epson 870 vm-s test
> strips that used the standard MIS VM curves for that machine -- they are
> close, with no significant flat spots or posterization.  They are a bit
> darker than the standard MIS VM test strips, but well within a useable
> range.  So, the first thing to check if the vm-sepia inkset produces bad
> results with all the standard vm curves is the settings in the driver.
>
> What I have noticed most is that the standard MIS VM "warm" curve -- which
> withholds the toner -- often does not work as well as the other standard
> curves.  By withholding the toner, the vm-s prints should be relatively
> neutral.
>
> The reality of these -- and no doubt most other -- inks is that while the
> densities of the vm-sepia match those of the standard MIS VM inks at one
> point, they may not match at another level of application.  That is, the
> response curves of the two inksets are not completely linear.   I suspect
> that because of this, the more radical the curves, the more likely that
the
> non-linear responses of the inks on the paper will show up.
>
> Many of the MIS VM "warm" curves I've done have very radical "green"
curves
> that totally withhold the toner until absolutely necessary to "turn on"
the
> black ink.  While this often works for the MIS VM inkset (depending on
> whether the particular driver can handle that steep a curve without
> artifacts), it can result in less-than-optimal tone distributions in the
> vm-sepia inkset (midtones that are too cool and make the shadows look
> warm -- which they are), and sometimes -- but not always -- uneven density
> distributions.
>
> With my quad printers (1160 & 3000) I get very nice "neutral" curves by
> putting some sepia toner in the mix all the way.  The resulting prints are
> dead neutral (X-Rite spectrophotometer readings: c=m=y) in the midtones,
> rolling off to the paper white in the highlights and black ink warm (y = c
+
> 0.03) starting at about 75%.
>
> The 870 is the first hextone machine I've tried to adjust, and I must say
> that the neutral curve did not end up quite as nicely as I would have
liked.
> The shadows get slightly warmer than they do with the quadtone machines,
> with a peak of about 0.04 units warm at 90%.  For example, the 870 neutral
> curve I made has X-Rite readings at 90% as follows: c=1.38, m=1.41,
y=1.42.
> This is OK, but will get more so with warming.  For example, in the fade
> test currently being done with this inkset, after the first 100 hours the
> 90% warmth was up to 0.05 units.  (70% was dead neutral.)
>
> (A new "non-warming"  toner has knocked 0.01 units or warmth off the 90%
> point at start and at 100 hours, but we'll just have to see how it looks
> after much more testing.  The "non-warming" (really just more stable over
> time) toner has a slightly lower gamut, but still has very ample tone to
> make full sepia prints.)
>
> So, what I have found, in general, is that making a curve that is between
> the "warm" and "mw" curves usually makes for better "neutral" vm-s prints.
> However, the hextone machines may not do quite as well at the neutral end
of
> the spectrum as do the quadtone machines.  See the 870 vm-s test strips
that
> are posted.  Go to the Files section of this forum:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> Then follow the links to
> Ink Sets > MIS > MIS Variable Mix > MIS VM Neutral-Sepia.  The image is
> called, "VM-Sepia-Standard 870 v. 1 curves.jpg."
>
> To make a better neutral curve for the vm-sepia inkset, start with the
> better of the "warm" or "mw" curve and move the "green" (toner curve)
> points -- very little if at all in the deep shadows, but so that they roll
> off to close to horizontal by about the 50% point, but still not at the
top
> of the curves box.  For each green point that is moved, for example, up if
> starting with the "mw" curve, move the blue point curve that many points
> down to offset the density change.  The blue curve ink (yellow ink
position)
> in a hextone vm machine is the lightest gray ink.  It is a hair lighter
than
> the dark toner, and a bit darker than the light/photo toner (green ink
> curve/magenta ink position).  So, offsetting moves keep the densities
about
> right.  Some final tweaking will be necessary.  Print 21-step test strips
to
> see the results of moves.
>
> These Photoshop adjustment curves can be a bit tricky.  For those who have
> not worked with curves, you might want to check out how the vm-s inkset is
> working for others with the machine you have before diving in.
>
> The vm-sepia is what I use as my regular inkset in the 3000, and I'm very
> pleased with it.  However, with other machines, there may not be curves
that
> have been fine-tuned for this inkset.
>
> Good luck.
>
> Paul
> http://www.PaulRoark.com
>
>
>
>
>
> [Non-text portions of this message have been removed]
>
>
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