Digital BW, The Print

Hi, Does anyone have an answer to obtaining neutral tone B+W images
when printing as a CMYK file. I'm a photographer in the UK putting
together a 62 page photobook for a client who wants the book in B+W,
the company which produce the books for me need  pdf files created in
photoshop coverted to CMYK as they print on a commercial printing press,
I've just had the books back and many of the pages have printed with
slightly differing hues, mainly yellow, some blue. Having read many
posts it would seem it is very hard to obtain neutral tones due to the
difficulty of mixing the CMY inks to produce neutral B+W, however I'm
hoping there is an answer out there somewhere! David
www.blinkweddings.co.uk

David,

one approach is to only use the black channel, leaving CMY channels
blank (white).
This means K will carry the full tonal range of the image.

As an enhancement you may try to duplicate the image as it appears in
the K channel to the other channels, then apply a curve that limits
the range to only the deepest shadows for CMY. This will produce a
richer "black" without mixing primaries across the grayscale.

In doing so, you have to make sure you do not exceed the maximum ink
(total of the highest percent in each plate) allowed by the press and
paper. That is never 400% (100% x 4 for each plate). It is around 240%
for newsprint and mid 300s for the higher end. You do have to find out
what applies in your case.


Antonis

  



--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "d.burges"
<davidburges@...> wrote:
.....

> slightly differing hues, mainly yellow, some blue. Having read many
> posts it would seem it is very hard to obtain neutral tones due to the
> difficulty of mixing the CMY inks to produce neutral B+W, however I'm
> hoping there is an answer out there somewhere! David
> www.blinkweddings.co.uk
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "d.burges"
<davidburges@...> wrote:
>
> Hi, Does anyone have an answer to obtaining neutral tone B+W images
> when printing as a CMYK file. I'm a photographer in the UK putting
> together a 62 page photobook for a client who wants the book in B+W,
> the company which produce the books for me need  pdf files created in
> photoshop coverted to CMYK as they print on a commercial printing press,
> I've just had the books back and many of the pages have printed with
> slightly differing hues, mainly yellow, some blue. Having read many
> posts it would seem it is very hard to obtain neutral tones due to the
> difficulty of mixing the CMY inks to produce neutral B+W, however I'm
> hoping there is an answer out there somewhere! David
> www.blinkweddings.co.uk
>

David, 
I just sent such a job to press.  Came back totally neutral using CMYK
builds.  Black only can sometimes look a little weak on press, and
since it is only a single plate, can also look at bit "grainy",
especially if you have color images on the same spread.  

If you are starting with RGB files, you can separate to a Rich Black
using either Heavy GCE or Max GCR (gray component replacement).  This
will give you a heavy black plate, and a "bump" in the CMY plates for
extra richness.  Using heavy or max GCR insures that a LOT of black in
is laid down, so it is unlikely you will have a color shirt on press.
 A blend of 50c/40m/40y combined with about 90-100K in the darkest
black areas will give you a very solid rich black.  Most presses are
pretty close to dead neutral with the above CMY values in the midtones.  

Since you don't want or need color, you can actually use Photoshop's
custom CMYK for this quite effectively.  Go to Color Settings, in the
CMYK dropdown box, select Custom CMYK, select Maximum GCR, 100 Black
Ink Limit, 300 Total Ink Limit, and enter 40 or 50 in the UCA Amount
box.  UCA is "undercolor addition" which throws a blend of CMY into
the mix, especially in the shadows.  Entering a value of 50 will give
you about 50c/40m/440y in the darkest shadows.  Click OK, then, when
you get back to the Color Settings dialog box, DO NOT CLICK SAVE, but
go to the CMYK dropdown box again and from there, click on Save CMYK.
 Name it whatever you want (ie, MAX-K_with50UCA) and click the Save
button.  This will create an ICC profile that you can use in the
future for conversions from Photoshop.  When you get back to the Color
Settings dialog, click CANCEL, since your probably do NOT want to save
this new profile as part of your standard settings in Photoshop.  

If you are doing the CMYK conversions, this will give you a very
strong Black with a bump of CMYK to add depth and density.  When you
create your PDF, you may wish to strip all profiles and send them an
untagged CMYK PDF file, so they do "reseparate" the file and screw up
the great blacks you created.  If they do reseparate, who knows what
they might do?

If you are starting with CMYK files, you probably need to have a
discussion with your printer to find out their formulas for neutrality
on press.  I'd still strive for heavy usage of black inks and much
lower values for CMY inks.  Whether you are in the US, UK, or far
east, most presses come pretty close to neutral with a mix of
50c/40m/40y.  The kicker is at the light end where being slightly off
neutral is more evident to the eye.  Using heavy or Max GCR is a good
way to go if you want to stay close to the neutral axis.  If you want
toned prints (brown, sepia, etc) it can still be a decent option,
since the heavy black should keep color drift to a minimum.  

Lou

On Feb 23, 2009, at 10:13 AM, d.burges wrote:

> Hi, Does anyone have an answer to obtaining neutral tone B+W images
> when printing as a CMYK file. I'm a photographer in the UK putting
> together a 62 page photobook for a client who wants the book in B+W,
> the company which produce the books for me need  pdf files created in
> photoshop coverted to CMYK as they print on a commercial printing  
> press,
> I've just had the books back and many of the pages have printed with
> slightly differing hues, mainly yellow, some blue. Having read many
> posts it would seem it is very hard to obtain neutral tones due to the
> difficulty of mixing the CMY inks to produce neutral B+W, however I'm
> hoping there is an answer out there somewhere! David

Color management will typically improve results, but if similarly  
prepared files are coming out warm in some pages and cool on others,  
than it would appear that the presses are not being run in a color  
managed manner, or to tight enough standards to get consistent  
results. The simple way to assure that files don't get color casts is  
to create black-channel-only separations, where the entire image is  
printed with only black ink, no colored inks blended in. This does not  
allow control of the tone (whatever gray the black ink produces is  
what you get) and may result in less smooth images, as there is only  
one ink being used, but if your current results are unacceptable, it  
might be an improvement.

C. David Tobie
Global Product Technology Manager
Digital Imaging & Home Theater
CDTobie@...


  ----------



Datacolor
www.datacolor.com/Spyder3




[Non-text portions of this message have been removed]

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, C D Tobie
<CDTobie@...> wrote:
>
> 
> On Feb 23, 2009, at 10:13 AM, d.burges wrote:
> 
> > Hi, Does anyone have an answer to obtaining neutral tone B+W images
> > when printing as a CMYK file. I'm a photographer in the UK putting
> > together a 62 page photobook for a client who wants the book in B+W,
> > the company which produce the books for me need  pdf files created in
> > photoshop coverted to CMYK as they print on a commercial printing  
> > press,
> > I've just had the books back and many of the pages have printed with
> > slightly differing hues, mainly yellow, some blue. Having read many
> > posts it would seem it is very hard to obtain neutral tones due to the
> > difficulty of mixing the CMY inks to produce neutral B+W, however I'm
> > hoping there is an answer out there somewhere! David
> 
> Color management will typically improve results, but if similarly  
> prepared files are coming out warm in some pages and cool on others,  
> than it would appear that the presses are not being run in a color  
> managed manner, or to tight enough standards to get consistent  
> results. The simple way to assure that files don't get color casts is  
> to create black-channel-only separations, where the entire image is  
> printed with only black ink, no colored inks blended in. This does not  
> allow control of the tone (whatever gray the black ink produces is  
> what you get) and may result in less smooth images, as there is only  
> one ink being used, but if your current results are unacceptable, it  
> might be an improvement.
> 


I would tend to agree here. Since the color casts vary, you might need
a better printing company or to change the way you do things with the
press. The heavy GCR is a step in the right direction, but as
mentioned above you might need to convert everything into the black
plate to get really neutral prints on a press that swings from yellow
to blue.

Instead of fighting the color issues, would it make sense to go with a
duotone? That way you might be able to control the color cast so that
all the pages were at least the same/similar color. It should improve
the apparent resolution in the lighter tones too. Maybe a tritone with
one color in the highlights and another in the dark tones.

One question also comes to mind... Is it really on a plate press, or
is it on a digital electrophotographic "press"? A lot of the
electrophotographic systems get put on the cheap end when the company
doesn't buy the good color managed RIP to drive them, or they don't
invest in color management tools and techniques to keep them neutral.

Definitely find out what the maximum ink load is for this machine with
your preferred paper. You might even ask them for the lab values of
each ink, and the secondaries so that you can build the proper CMYK
set up into Photoshop. You never know, they might actually know the
answer to that question.

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Greg"
<dfaprinting@...> wrote:

> Definitely find out what the maximum ink load is for this machine with
> your preferred paper. You might even ask them for the lab values of
> each ink, and the secondaries so that you can build the proper CMYK
> set up into Photoshop. You never know, they might actually know the
> answer to that question.
>

Greg,

If you are talking about inputting Lab values for R/G/B/C/M/Y/K into
Photoshop's Custom CMYK dialog boxes, it doesn't work properly. 
Unfortunately, Custom CMYK is an old, outdated module with a lot of
kludges, modifications, and kinks.  It "should" work this way, but it
doesn't.  I believe in an ICC color managed workflow, especially for
color work, but for B&W, Custom CMYK can be made to work pretty well.
 If they are going the color managed route with a good ICC press
profile (or an industry standard profile like SWOP, G7, etc) I'd still
encourage heavy GCR usage to reduce variability and color casts.  Or,
as you and others have mentioned, straight B&W or duotones.  I agree,
digital presses and laser units are a whole different ballgame, and it
is hit or miss.  

I like the idea of a duotone or tritone, but that may cost him extra
on a press due to special inks, setups, cleanup, etc.  Using Max GCR
with some undercolor addition is usually pretty safe for B&W, even if
the process control is less than stellar, since there is more black
ink compared to the CMY inks, and the black ink has nearly triple the
influence of any single CMY ink on press.  

Lou

This one is especially interesting, there is concern about the way the  
printing company manage the flow
as the files are swinging from yellow to blue???

> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, C D Tobie
> <CDTobie@...> wrote:
> >
> >
> > On Feb 23, 2009, at 10:13 AM, d.burges wrote:
> >
> > > Hi, Does anyone have an answer to obtaining neutral tone B+W  
> images
> > > when printing as a CMYK file. I'm a photographer in the UK putting
> > > together a 62 page photobook for a client who wants the book in B 
> +W,
> > > the company which produce the books for me need pdf files  
> created in
> > > photoshop coverted to CMYK as they print on a commercial printing
> > > press,
> > > I've just had the books back and many of the pages have printed  
> with
> > > slightly differing hues, mainly yellow, some blue. Having read  
> many
> > > posts it would seem it is very hard to obtain neutral tones due  
> to the
> > > difficulty of mixing the CMY inks to produce neutral B+W,  
> however I'm
> > > hoping there is an answer out there somewhere! David
> >
> > Color management will typically improve results, but if similarly
> > prepared files are coming out warm in some pages and cool on others,
> > than it would appear that the presses are not being run in a color
> > managed manner, or to tight enough standards to get consistent
> > results. The simple way to assure that files don't get color casts  
> is
> > to create black-channel-only separations, where the entire image is
> > printed with only black ink, no colored inks blended in. This does  
> not
> > allow control of the tone (whatever gray the black ink produces is
> > what you get) and may result in less smooth images, as there is only
> > one ink being used, but if your current results are unacceptable, it
> > might be an improvement.
> >
>
> I would tend to agree here. Since the color casts vary, you might need
> a better printing company or to change the way you do things with the
> press. The heavy GCR is a step in the right direction, but as
> mentioned above you might need to convert everything into the black
> plate to get really neutral prints on a press that swings from yellow
> to blue.
>
> Instead of fighting the color issues, would it make sense to go with a
> duotone? That way you might be able to control the color cast so that
> all the pages were at least the same/similar color. It should improve
> the apparent resolution in the lighter tones too. Maybe a tritone with
> one color in the highlights and another in the dark tones.
>
> One question also comes to mind... Is it really on a plate press, or
> is it on a digital electrophotographic "press"? A lot of the
> electrophotographic systems get put on the cheap end when the company
> doesn't buy the good color managed RIP to drive them, or they don't
> invest in color management tools and techniques to keep them neutral.
>
> Definitely find out what the maximum ink load is for this machine with
> your preferred paper. You might even ask them for the lab values of
> each ink, and the secondaries so that you can build the proper CMYK
> set up into Photoshop. You never know, they might actually know the
> answer to that question.
>
>
> 



[Non-text portions of this message have been removed]

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, David Burges
<davidburges@...> wrote:
>
> This one is especially interesting, there is concern about the way the  
> printing company manage the flow
> as the files are swinging from yellow to blue???

David,

I played around with a few conversion techniques (sRGB to CMYK) for
B&W images.  Thought you might be interested.  

Using Photoshop's Custom CMYK, I created separation parameters as
follows:  SWOP, 20% dot gain (you may need to use a different dot gain
depending on the press and paper), Maximum GCR, 100K, 240 Total Ink,
and 50 UCA.  The nice thing about this profile is that it will give
you a deep black, and could be used on nearly any output media, from
newsprint to fine coated stock (but you have to input the correct dot
gain for the paper/press combination).  

Then I created a 21 step grayscale in Photoshop, and converted to the
above profile using Perceptual intent (which I recommend for B&W
conversions, since you don't have to worry about losing color
saturation).  Pure black separates out to 44c/33m/32y/100K.  Middle
Gray separates to 2/1/1/59.  When you reach an RGB value of
153/153/153 (about 40% gray) all color inks have been removed from the
equation, and you get 0c/0m/0y/48K.  From this point all the way to
paper white, you have nothing but black ink being used.  The above
separation is pretty much guaranteed to give you a very neutral B&W on
press, unless you dealing with complete incompetents (and even then it
should be hard to screw up).  The very high percentage of K ink on
press will keep your file neutral, even if there is significant drift
or poor process control.  

The only thing I don't like about the Custom CMYK approach for B&W is
that the color inks drop off so quickly and you may see some
graininess in the 1/4 tones and highlights, since output nothing but
black ink.  To get those lighter tones, the ink dots will be smaller
and spread apart, so more paper white will show through.  But, for
B&W, Custom CMYK is a great solution if you don't have access to
profiling equipment.  

If you DO have access to good profiling software (ProfileMaker5,
Monaco Profiler, etc) a more elegant solution is to create your own
profile from available characterization data, using Max GCR.  Good
software will allow you to set the black and total ink limits, where
the black ink begins, saturation levels, etc.  With a profile like
this, you can still retain a high percentage of black ink throughout
the tonal range for stability and neutrality, but you can allow the
color inks to tail off a little more slowly as you approach paper
white.  For example, I built a profile using ProfileMaker5 and
characterization data from the Gracol G& data set, (which I used on a
recent job), using Max GCR, 100K, 320 Total Ink Limit, and Black start
at 0% black (ie, paper white).  Using this profile for conversion from
sRGB to CMYK gave me a value of 2c/2m/3y/3K in the 5% gray highlight
area.  A 25% gray will print as 7c/6m/8y/21K, which is pretty much
guaranteed to be black.  The results will be smoother in the
highlights, since you are adding a little bit more CMY ink to the
black ink.  Since black ink is about 3X as powerful as individual CMY
inks, neutrality is very likely, especially on a well run press.  Even
if the CMY inks drift a little, you should get a pretty neutral
result.  Not quite as bullet-proof as Custom CMYK, but it will be
smoother.  The Max GCR should keep your file safe from unwanted color
drift.  

In either case, you can tweak the K channel of the CMYK file after
conversion to adjust shadows, without affecting the color.  Either
approach works great for neutral B&W using 4/C process inks.  Your
route will depend on whether you have access to profiling software,
and the final result you want.  

Regards,

Lou

I guess I'd err on the side of a duotone/tritone files. If you depend
on just the process black ink printing on your black plate only,
you'll end up with gray, not black. 

You could ask the printer to print in a Pantone black rather than a
process black, and do it in one color only. YOu might want to consider
 doing duotone files with the varied Pantone blacks. There is a good
range of shades of black and you can create some really nice
variations in your files with just that touch of color. then, you
don't have to worry as much about the ink coverage on the rollers on
the press (if this is traditional web printing, which it most likely
is, considering your issues with variation in color). By using Pantone
blacks, even if it goes out of register, or the ink varies a bit on
the rollers, you'll still get the same tone on each image and not have
the issues of blue/yellow/magenta toning your images. 

And, the text on your pages will still be true black, because you'll
be specifying them in a Pantone black, rather than process black.

just one more option.
Jane

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, David Burges
<davidburges@...> wrote:

>
> This one is especially interesting, there is concern about the way the  
> printing company manage the flow
> as the files are swinging from yellow to blue???
> 
> > --- In DigitalBlackandWhiteThePrint@yahoogroups.com, C D Tobie
> > <CDTobie@> wrote:
> > >
> > >
> > > On Feb 23, 2009, at 10:13 AM, d.burges wrote:
> > >
> > > > Hi, Does anyone have an answer to obtaining neutral tone B+W  
> > images
> > > > when printing as a CMYK file. I'm a photographer in the UK putting
> > > > together a 62 page photobook for a client who wants the book in B 
> > +W,
> > > > the company which produce the books for me need pdf files  
> > created in
> > > > photoshop coverted to CMYK as they print on a commercial printing
> > > > press,
> > > > I've just had the books back and many of the pages have printed  
> > with
> > > > slightly differing hues, mainly yellow, some blue. Having read  
> > many
> > > > posts it would seem it is very hard to obtain neutral tones due  
> > to the
> > > > difficulty of mixing the CMY inks to produce neutral B+W,  
> > however I'm
> > > > hoping there is an answer out there somewhere! David
> > >
> > > Color management will typically improve results, but if similarly
> > > prepared files are coming out warm in some pages and cool on others,
> > > than it would appear that the presses are not being run in a color
> > > managed manner, or to tight enough standards to get consistent
> > > results. The simple way to assure that files don't get color casts  
> > is
> > > to create black-channel-only separations, where the entire image is
> > > printed with only black ink, no colored inks blended in. This does  
> > not
> > > allow control of the tone (whatever gray the black ink produces is
> > > what you get) and may result in less smooth images, as there is only
> > > one ink being used, but if your current results are unacceptable, it
> > > might be an improvement.
> > >
> >
> > I would tend to agree here. Since the color casts vary, you might need
> > a better printing company or to change the way you do things with the
> > press. The heavy GCR is a step in the right direction, but as
> > mentioned above you might need to convert everything into the black
> > plate to get really neutral prints on a press that swings from yellow
> > to blue.
> >
> > Instead of fighting the color issues, would it make sense to go with a
> > duotone? That way you might be able to control the color cast so that
> > all the pages were at least the same/similar color. It should improve
> > the apparent resolution in the lighter tones too. Maybe a tritone with
> > one color in the highlights and another in the dark tones.
> >
> > One question also comes to mind... Is it really on a plate press, or
> > is it on a digital electrophotographic "press"? A lot of the
> > electrophotographic systems get put on the cheap end when the company
> > doesn't buy the good color managed RIP to drive them, or they don't
> > invest in color management tools and techniques to keep them neutral.
> >
> > Definitely find out what the maximum ink load is for this machine with
> > your preferred paper. You might even ask them for the lab values of
> > each ink, and the secondaries so that you can build the proper CMYK
> > set up into Photoshop. You never know, they might actually know the
> > answer to that question.
> >
> >
> > 
> 
> 
> 
> [Non-text portions of this message have been removed]
>

David,

Sorry for bombarding you, but I thought of one more good approach for
printing 4/C B&W that will maintain neutrality on press.  

Do a standard RGB to CMYK conversion, using one of the industry
standard CMYK profiles (US Web Coated SWOP, Euroscale Coated, etc). 
This will give you a full 4/C conversion with too much color to
guarantee neutrality on press.

To solve this, create a new Selective Color adjustment layer.  Set the
Method to "Absolute" the select "Blacks" from the drop down menu. 
Nove the Cyan, Magenta, and Yellow Sliders to the left in equal
amounts to a figure like -40 or -50.  Make sure they are all adjusted
by the EXACT same percentage.  This will take color inks out of your
blacks in equal proportions.  With your mouse cursor positioned over
the darkest black portion of the image, read the "K" value in the Info
Palette.  If it is currently reading 90K, move the Black slider in
Selective color to to the right to increase the back ink.  Don't go
past 100% K, and keep an eye on shadow detail to prevent blocking up.
 It is probably better to be conservative and keep the K value between
93 and 96% or so.  This selective color adjustment will change your
file so that black ink greatly outweighs color inks throughout for
neutral blacks.  

For further refinement, you can even use the "Neutrals" drop down box
in Selective Color and play with those settings in a similar fashion,
but you probably won't need it.  This approach will be more like
creating a custom profile with ProfileMaker or Monaco Profiler, since
you still will have a little color in the highlights, but a lot more
black than color.

Finally, you can tweak the black channel after this adjustment for the
best shadow detail and tonal range, but leave the CMY channels alone.  

Lou

If this is being printed with an Indigo, like the on line books etc.,
it's a well known problem for B&W. The system is very hard to keep
consistant, and primarily best for color since the problems will be
less noticeable from page to page.
There may be ways to minimize with a conversion technique, but you are
up against the limitations of the process at some point. Can you even
be sure your CMYK will remain intact down the line?
Tyler
http://www.custom-digital.com/

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "d.burges"
<davidburges@...> wrote:

>
> Hi, Does anyone have an answer to obtaining neutral tone B+W images
> when printing as a CMYK file. I'm a photographer in the UK putting
> together a 62 page photobook for a client who wants the book in B+W,
> the company which produce the books for me need  pdf files created in
> photoshop coverted to CMYK as they print on a commercial printing press,
> I've just had the books back and many of the pages have printed with
> slightly differing hues, mainly yellow, some blue. Having read many
> posts it would seem it is very hard to obtain neutral tones due to the
> difficulty of mixing the CMY inks to produce neutral B+W, however I'm
> hoping there is an answer out there somewhere! David
> www.blinkweddings.co.uk
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Louis Dina"
<lou@...> wrote:
>
> David,
> 
> Sorry for bombarding you, but I thought of one more good approach for
> printing 4/C B&W that will maintain neutrality on press.  
> 
> Do a standard RGB to CMYK conversion, using one of the industry
> standard CMYK profiles (US Web Coated SWOP, Euroscale Coated, etc). 
> This will give you a full 4/C conversion with too much color to
> guarantee neutrality on press.
> 
> To solve this, create a new Selective Color adjustment layer.  Set the
> Method to "Absolute" the select "Blacks" from the drop down menu. 
> Nove the Cyan, Magenta, and Yellow Sliders to the left in equal
> amounts to a figure like -40 or -50.  Make sure they are all adjusted
> by the EXACT same percentage.  This will take color inks out of your
> blacks in equal proportions.  With your mouse cursor positioned over
> the darkest black portion of the image, read the "K" value in the Info
> Palette.  If it is currently reading 90K, move the Black slider in
> Selective color to to the right to increase the back ink.  Don't go
> past 100% K, and keep an eye on shadow detail to prevent blocking up.
>  It is probably better to be conservative and keep the K value between
> 93 and 96% or so.  This selective color adjustment will change your
> file so that black ink greatly outweighs color inks throughout for
> neutral blacks.  
> 
> For further refinement, you can even use the "Neutrals" drop down box
> in Selective Color and play with those settings in a similar fashion,
> but you probably won't need it.  This approach will be more like
> creating a custom profile with ProfileMaker or Monaco Profiler, since
> you still will have a little color in the highlights, but a lot more
> black than color.
> 
> Finally, you can tweak the black channel after this adjustment for the
> best shadow detail and tonal range, but leave the CMY channels alone.  
> 
> Lou
>

David,

Trash the above method.  On further experimentation, it's a dog.  The
intial separation to an industry standard CMYK profile (SWOP,
Euroscale, etc) leaves the black plate totally blank in the
highlights, and it's too much fuss trying to get detail back into the
black plate.  Sorry for the wild goose chase.  

The other two methods (Photoshop Custom CMYK with Max GCR and building
a Max GCR profile with high end profiling software) work fine though.  

Tyler makes an excellent point on what can happen to your file once it
is out of your hands.  If the printer does a conversion of your file
to their "standard", they may totally undo all your hard work and give
you a standard separation once again (ie, lots of color in the CMY
plates and a lower black in the K plate).  In an attempt to guard
against that, you can strip your profiles from the files entirely
before submitting them.  However, if your service provider is
determined to do a conversion, they will then assume a profile for the
source space or just use their default color space for CMYK as source
and hose your file.  

Then only solution I know is to deal with a knowledgeable printer who
understands this stuff and communicate clearly that your files NOT be
adjusted or converted.  This way, your numbers will be sent to the
press.  It's a tough game working with printers.  Communication is
paramount, and working with someone who has a clue also helps!  Many
printers don't.  

Lou

Thank all so much for your advice, I'm having a meeting with the
company on Thursday, so I'll be taking your ideas along with me to see
what they think, I'll let you know!

David