Digital BW, The Print

Marketa,

You wrote:

>I just got the MIS VM inks for my Epson 1200 and am trying to figure out
>general guidelines on how to adjust the curves for my system.

I assume you have started out with the pre-made curves for the specific
printer and computer (PC or Mac) that you have.  If not get those curves
(free) from MIS or me.

>...blue ink is increased by adding more magenta,
>midtones by adding more cyan and light tones by adding
>more yellow at the appropriate place on the curve.

Yes, that is basically it.  Adding toner will also increase the density at
that spot as well as make the tone cooler.

>... what's the best way to compensate with other
>inks when you change the proportion of one ink.

The cold toner is just a hair darker than the yellow ink.  So, where you
move the toner x units in one direction, compensate by moving the yellow ink
(blue curve) x units in opposite direction.

> For example, I wanted a warmer print in the midtones
>so I increased green, but as a result that area
>of the wedge also became lighter. Should I add more cyan

For a warmer print, I assume you moved the green curve (magenta-position
ink, and thus the toner in a 6-ink printer) toward the lighter end of the
axis.  That is, you would want less of the toner ink.

Note, the curves graph can use either the 0% - 100% ink percentages or the
0 - 255 8-bit luminance scale.  One switches methods/scales by  clicking on
the double arrow in the horizontal axis.

I use the 0 - 255 scale because it gives you more control. With this scale
the darkest point is the bottom left corner of the graph.  This is point
(0,0).

So, on this axis, to increase warm, one needs to decrease the cold toner.
Thus move the green curve (magenta ink) up, toward the lighter end of the
vertical axis.

To compensate for less toner ink, move the corresponding point of the blue
curve (yellow/light gray) ink down to add more ink.

>or should I modify the transfer function

No, I would not touch the Transfer Function in this case.  Use the curves
and be sure to save the new curve with a different name.

Good luck.  I'm glad to see people getting in there and learning these
controls.  You can really custom design the look to what you want.

Paul
http://www.PaulRoark.com

Paul,
Thank you so much for your advice.

I do have your curves for the 1200 but I wanted to start with something 
simple. I tried adjusting yours but made a mess of it because of their 
complexity. The problem I am having with your curves is little 
differentiation between the steps in the darker midtones that wipe out most 
of the detail in those areas. The lighter areas come out pretty accurate. 

I started with no curve at all using all the inks and made a transfer 
function for that. The wedge came out pretty good but the midtones were a 
little too cool, so I decided to do a neutral curve by adding green to the 
midtones. 

Thanks for telling me to use the "yellow" ink to compensate when I reduce the 
blue, I did not think of that. I am quite comfortable with Photoshop so I do 
know how to use Curves.

By the way, what do you mean by toner? The lighter blue ink? I am very new to 
all of this so please bear with me.

Another elementary question: how close do you try to get the RGB values for a 
neutral print? I print the wedge, scan it, set the black and white point and 
then measure the RGB and K values with the eyedropper. (I hope I am doing 
that right.) My RGB readings for my neutral curve are within 1-4 units of 
each other for each step. Is that close enough? 

Also, how do you decide on the RGB values for the toned prints? That's my 
next step after I master the neutral one.

Thanks again,

Marketa

Marketa,

>... The problem I am having with your curves is little
>differentiation between the steps in the darker midtones that wipe out most
>of the detail in those areas. The lighter areas come out pretty accurate.

If you use color space sRGB, try changing to Adobe RGB.  The main difference
is the shadow separation.  Then again, the problem may just be that you have
early draft curves.  The 1200 is still in process.

What computer do you use -- Mac or PC?

>...what do you mean by toner? The lighter blue ink?

Yes, the toner is the light blue ink in the MIS VM inkset.  It is in the
magenta position.

>... how close do you try to get the RGB values for a neutral print?

Well, dead neutral would be all equal, of course.  For the "nc" curve,
however, I build in a little blue to offset the warm shift -- by about half.
Of course, the paper choice affects this also.  So, the target for the "nc"
curve is blue channel 4 units greater than red channel.  This tapers toward
the ends.  I try to get the adjacent steps in the midtones within 1 unit of
the target.  Printer-to-printer and print-session-to-print-session
variances, however, make it difficult to say how far off these get in the
real world.

>... how do you decide on the RGB values for the toned prints?

The "nc" curve is explained above.  The Cool curve was the coolest I found
to be within the "normal" look of a silver print.  That is, it doesn't look
outright blue.  It's 9 units cool.  The warm curve is maximum warmth
(minimum toner) consistent with there not being too many artifacts (usually
humps in the g/s ramp that won't go away.  The "mw" is about half way to
that point -- target 6 units warm (red over blue).

Paul
http://www.PaulRoark.com

Paul,

<< If you use color space sRGB, try changing to Adobe RGB.  The main 
difference
 is the shadow separation.  Then again, the problem may just be that you have
 early draft curves.  The 1200 is still in process. >>

I printed a wedge using Adobe RGB instead of sRGB as print space but the 
results were the same - almost no differentiation between roughly 70 and 90 
%. Then I tried the Epson 1200 print space and that was actually closer. I 
may try to modify the curve to print with the 1200 print space. By the way I 
have a PC and PS6 and I am working with your medium warm curve.

I'll keep working on it. This process is interesting to me because it forces 
me to think about what's going on and understand the basic principles. I'll 
let you know when I have something useable.

Thanks,
Marketa