Seeing Green.....


Jim Donovan
 

Hello, Long story short. I had a cover signature offset print with a greenish cast to it that I know is incorrect,shifted on press for sure. Rest of the magazine looked acceptable. Did some epson proofs of interior pages and they were acceptable, the print result of the cover is quite a bit off from my epsons. We just look for eye pleasing color, not color matching and we do not have everything profiled and will not be doing so. I know it's not proper but it's the world I have to live in.

 My question is very general. Obviously you need a -a value for green. I would like some opinions on how negative a must be to start showing a  greenish cast? -1a 1b? -2a 5b? -3a 3b? Seems to me that you need -3/-4 and up(more negative) to really start seeing a noticeable greenish cast?

 I fully realize all the variables and the amount of them that contribute to a color shift in offset printing, again just a general opinion is all I am seeking. Will speak with the printer tomorrow about the cover sig, always happy with their work, this one just slipped on them. Thank You, Jim Donovan

 


Henry Davis
 

Was the printer given CMYK files?
Would a green cast be expected from the CMYK build(s) found in the cover?

Some specific values from the file given to the printer might be helpful.

Henry Davis

On Feb 15, 2016, at 5:38 PM, Jim Donovan jim@harrispublishing.com [COLORTHEORY] wrote:
<Snip>


Hello, Long story short. I had a cover signature offset print with a greenish cast to it that I know is incorrect,shifted on press for sure. Rest of the magazine looked acceptable. Did some epson proofs of interior pages and they were acceptable, the print result of the cover is quite a bit off from my epsons. We just look for eye pleasing color, not color matching and we do not have everything profiled and will not be doing so. I know it's not proper but it's the world I have to live in.


Rick Gordon
 

I find that, to my eye, a green cast in neutrals can be perceived at very low (even -1 or -2 a values, with b positive or negative). I personally seem to be able to tolerate a notch too much a+ than a slightly a-negative value, particularly if the b value is positive, and sometimes have targeted a-negative/b-positive neutrals to set slightly a-negative values to 0.

Also, a touch too much a-negative can be blown further in the wrong direction by MMM, and I've sometimes had to resort to blocking that area of the spectrum from MMM when neutrals may be affected. I understand that MMM is supposed to minimize changes in neutrals, but a situation like an off-white wall where the warmth is not uniform due to natural lighting conditions (particularly with higher-ISO images) can be problematical.

Rick Gordon

---------------------

On 2/15/16, 2:38 PM, Jim Donovan jim@... [COLORTHEORY] wrote:
Hello, Long story short. I had a cover signature offset print with a greenish cast to it that I know is incorrect,shifted on press for sure. Rest of the magazine looked acceptable. Did some epson proofs of interior pages and they were acceptable, the print result of the cover is quite a bit off from my epsons. We just look for eye pleasing color, not color matching and we do not have everything profiled and will not be doing so. I know it's not proper but it's the world I have to live in.

 My question is very general. Obviously you need a -a value for green. I would like some opinions on how negative a must be to start showing a  greenish cast? -1a 1b? -2a 5b? -3a 3b? Seems to me that you need -3/-4 and up(more negative) to really start seeing a noticeable greenish cast?

 I fully realize all the variables and the amount of them that contribute to a color shift in offset printing, again just a general opinion is all I am seeking. Will speak with the printer tomorrow about the cover sig, always happy with their work, this one just slipped on them. Thank You, Jim Donovan

___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com


Jim Donovan
 

 Thanks for the reply's. Yes they were given cmyk files and no the values do not justify the amount green cast that was produced.Had five different sets of eyes look at it, and 6 other pages we proofed and all of them agree, it's much greener than it should be. Did espon proofs of of 6 other pix in the same magazine from interior signatures and all are acceptable when compared to the print job. The epson proof varies noticeably from the cover that was printed. Also compared an ad that ran in the previous issue and this current issue that we are discussing on the cover signature that had a vehicle that had a black roof. It clearly has shifted toward green were it was previously a neutral black.

 Will speak with the printer today. They run all issues of this publication and will see when they compare that previous issue something( magenta is my guess)is amiss. They do a great job for us, this one just got away from them a bit.

 Amazing that your eye can pick up -1a in a neutral Rick! I would guess you are the exception! Jim Donovan



On Mon, Feb 15, 2016 at 10:29 PM, Rick Gordon lists@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

I find that, to my eye, a green cast in neutrals can be perceived at very low (even -1 or -2 a values, with b positive or negative). I personally seem to be able to tolerate a notch too much a+ than a slightly a-negative value, particularly if the b value is positive, and sometimes have targeted a-negative/b-positive neutrals to set slightly a-negative values to 0.

Also, a touch too much a-negative can be blown further in the wrong direction by MMM, and I've sometimes had to resort to blocking that area of the spectrum from MMM when neutrals may be affected. I understand that MMM is supposed to minimize changes in neutrals, but a situation like an off-white wall where the warmth is not uniform due to natural lighting conditions (particularly with higher-ISO images) can be problematical.

Rick Gordon

---------------------


On 2/15/16, 2:38 PM, Jim Donovan jim@... [COLORTHEORY] wrote:
Hello, Long story short. I had a cover signature offset print with a greenish cast to it that I know is incorrect,shifted on press for sure. Rest of the magazine looked acceptable. Did some epson proofs of interior pages and they were acceptable, the print result of the cover is quite a bit off from my epsons. We just look for eye pleasing color, not color matching and we do not have everything profiled and will not be doing so. I know it's not proper but it's the world I have to live in.

 My question is very general. Obviously you need a -a value for green. I would like some opinions on how negative a must be to start showing a  greenish cast? -1a 1b? -2a 5b? -3a 3b? Seems to me that you need -3/-4 and up(more negative) to really start seeing a noticeable greenish cast?

 I fully realize all the variables and the amount of them that contribute to a color shift in offset printing, again just a general opinion is all I am seeking. Will speak with the printer tomorrow about the cover sig, always happy with their work, this one just slipped on them. Thank You, Jim Donovan

___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com



Henry Davis
 

It would still be interesting if you could post some of the CMYK builds that turned out green.  The printer should have some interest in these values as well.  I couldn't tell from the posts if the cast was in a delicate pastel - but the previous Black area that went green suggests a problem with solid ink density on press (or a Black build that would tend Green).

There was no mention of any proofs supplied by the printer and it's not clear if the printer got a copy of the Epson prints that you made.  I would hesitate calling them "proofs" (especially at this point) as this puts a bad light on the printer that is possibly undeserved.  Had the printer provided proofs that had the unwanted green cast on the cover it would be a different story.

It might benefit others on the list if you tell how your Epson prints are made: direct from application to Epson printer or from application to RIP) and if profile conversions were made.

Again, original CMYK values along with a discussion of the workflow might help to discover whether the ball was dropped in the pressroom or prepress.  Preventing future problems will depend on an understanding and agreement about workflow and press procedures.  You seem to enjoy a good relationship with the printer and a friendly discussion about this run might result in an even better relationship - and better looking jobs.

Henry Davis

On Feb 16, 2016, at 10:18 AM, Jim Donovan jim@... [COLORTHEORY] wrote:

 

 Thanks for the reply's. Yes they were given cmyk files and no the values do not justify the amount green cast that was produced.Had five different sets of eyes look at it, and 6 other pages we proofed and all of them agree, it's much greener than it should be. Did espon proofs of of 6 other pix in the same magazine from interior signatures and all are acceptable when compared to the print job. The epson proof varies noticeably from the cover that was printed. Also compared an ad that ran in the previous issue and this current issue that we are discussing on the cover signature that had a vehicle that had a black roof. It clearly has shifted toward green were it was previously a neutral black.

 Will speak with the printer today. They run all issues of this publication and will see when they compare that previous issue something( magenta is my guess)is amiss. They do a great job for us, this one just got away from them a bit.


Rick Gordon
 

It's also amazing to me what I DON'T pick up sometimes. I think that when I see that, it's because I'm specifically looking for it.

So when I compare a 1-unit nudge to the a curve (or in the tint bar of ACR), I definitely find the difference noticeable, and tend to prefer the warmer one.

If it were without a comparative reference, I probably couldn't tell absolutely.

Rick Gordon

---------------------
On 2/16/16, 7:18 AM, Jim Donovan jim@... [COLORTHEORY] wrote:
Amazing that your eye can pick up -1a in a neutral Rick! I would guess you are the exception! Jim Donovan

___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com


Jim Donovan
 

 Sorry for the delayed response, just now heard back from the printer. Long and short of it is after pulling their copies to inspect, with the head pressman, plant manager and pressman who ran the signature they flat out said and I quote "We blew it!" This was an isolated incident, they do an outstanding job for us and have for the 20 years I have worked with them printing our publications. So this matter has been addressed and taken care of. I was just looking for opinions on when a green cast would start to really be evident, I knew my values were fine. Some cmyk values were around 64c 54m 57y 32k, 39c 33m 32y 19k and add or subtract 3,4 points in any number of ink combinations, the cover was a photo of a rock wall with values constantly changing with cracks, ledges and crevices. Nothing justified the green cast that was reproduced. Their magenta was off, it's the strongest ink and will make the biggest difference when off in my experience. It has happened to anyone who has sent 10's of thousands of pages to press and 100's of thousands of images to press as I have for our company over the last 20 years. If it hasn't it will.

 Would love to say we have a rip, are profiled, tagged, bagged and provide bullet-proof proofs, but the reality of the world I live in is that we are not, we don't and never will with the company I work for. We are not printing art repo, coffee table, fashion product matching publications were those procedures would be needed. We do eye pleasing nice solid niche publications that do just fine and we have lots of happy customers.They just blew this one, that simple, I'm sure they will not blow another. They will satisfy any issues should there be a complaint from an advertiser.

 Our procedures are fine. We provide hi-res cmyk pdf's to the two different print shops we use and they send them to press. Every photo that prints in our magazines(Unless it is a provided ad that is just a plug and play) is checked, corrected and processed by me.It's on me to make sure the cmyk files are solid. I know this will raise hackles and some will think it's not possible but the reality is you provide a good cmyk separations they are going to print good,even without tagged and profiled images,a proof, or ripped bullet proof files, unless there is an issue after we hand the file off somehow with the plate setter of press problems.We do it everyday. Anyone can always find something wrong with any proof vs the actual print job regardless of how careful the procedures. Thanx again for the input, Jim Donovan

On Tue, Feb 16, 2016 at 7:13 PM, Rick Gordon lists@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

It's also amazing to me what I DON'T pick up sometimes. I think that when I see that, it's because I'm specifically looking for it.

So when I compare a 1-unit nudge to the a curve (or in the tint bar of ACR), I definitely find the difference noticeable, and tend to prefer the warmer one.

If it were without a comparative reference, I probably couldn't tell absolutely.

Rick Gordon

---------------------
On 2/16/16, 7:18 AM, Jim Donovan jim@... [COLORTHEORY] wrote:

Amazing that your eye can pick up -1a in a neutral Rick! I would guess you are the exception! Jim Donovan

___________________________________________
RICK GORDON
EMERALD VALLEY GRAPHICS AND CONSULTING
___________________________________________
WWW: http://www.shelterpub.com



Henry Davis
 

Great Jim! I wish there were more specifics about the cause - was the SID wrong or the plate curve or was there some color management snafu. The slug color bar might be telling. Whichever, I'm glad that it's all working out and that the relationship is still good.

In spite of other opinions, I think your procedures are fine. Good separations have worked for ages and should always work. However, there have been situations where good separations have been ruined by bad color management. The color management era has offered more opportunities for color problems - an irony.

Henry Davis

On Feb 19, 2016, at 10:24 AM, Jim Donovan jim@harrispublishing.com [COLORTHEORY] wrote:
<Snip>


Sorry for the delayed response, just now heard back from the printer. Long and short of it is after pulling their copies to inspect, with the head pressman, plant manager and pressman who ran the signature they flat out said and I quote "We blew it!" This was an isolated incident, they do an outstanding job for us and have for the 20 years I have worked with them printing our publications. So this matter has been addressed and taken care of.

Our procedures are fine. We provide hi-res cmyk pdf's to the two different print shops we use and they send them to press. Every photo that prints in our magazines(Unless it is a provided ad that is just a plug and play) is checked, corrected and processed by me.It's on me to make sure the cmyk files are solid. I know this will raise hackles and some will think it's not possible but the reality is you provide a good cmyk separations they are going to print good,even without tagged and profiled images,a proof, or ripped bullet proof files, unless there is an issue after we hand the file off somehow with the plate setter of press problems.We do it everyday. Anyone can always find something wrong with any proof vs the actual print job regardless of how careful the procedures. Thanx again for the input, Jim Donovan


Jim Donovan
 

Good separations have worked for ages and should always work. However,
there have been situations where good separations have been ruined by
bad color management. The color management era has offered more
opportunities for color problems - an irony.

AMEN HENRY!!!! It was a magenta ink density problem on press. Jim Donovan

On Fri, Feb 19, 2016 at 9:37 AM, Henry Davis davishr@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

Great Jim! I wish there were more specifics about the cause - was the
SID wrong or the plate curve or was there some color management
snafu. The slug color bar might be telling. Whichever, I'm glad that
it's all working out and that the relationship is still good.

In spite of other opinions, I think your procedures are fine. Good
separations have worked for ages and should always work. However,
there have been situations where good separations have been ruined by
bad color management. The color management era has offered more
opportunities for color problems - an irony.

Henry Davis

On Feb 19, 2016, at 10:24 AM, Jim Donovan jim@...
[COLORTHEORY] wrote:


>
> Sorry for the delayed response, just now heard back from the
> printer. Long and short of it is after pulling their copies to
> inspect, with the head pressman, plant manager and pressman who ran
> the signature they flat out said and I quote "We blew it!" This was
> an isolated incident, they do an outstanding job for us and have for
> the 20 years I have worked with them printing our publications. So
> this matter has been addressed and taken care of.
>
> Our procedures are fine. We provide hi-res cmyk pdf's to the two
> different print shops we use and they send them to press. Every
> photo that prints in our magazines(Unless it is a provided ad that
> is just a plug and play) is checked, corrected and processed by
> me.It's on me to make sure the cmyk files are solid. I know this
> will raise hackles and some will think it's not possible but the
> reality is you provide a good cmyk separations they are going to
> print good,even without tagged and profiled images,a proof, or
> ripped bullet proof files, unless there is an issue after we hand
> the file off somehow with the plate setter of press problems.We do
> it everyday. Anyone can always find something wrong with any proof
> vs the actual print job regardless of how careful the procedures.
> Thanx again for the input, Jim Donovan



Dan Margulis
 

Jim Donovan writes,

 Amazing that your eye can pick up -1a in a neutral Rick! I would guess you are the exception! 

I suspect not. We are a lot more sensitive to things that are disagreeable. Color science alleges that a neutral that is (2)a0b (bluish green) is just as perceptibly non-gray as would be 0a(2)b (blue) or 1a1b (red). That may be true as a matter of optics but a greenish gray is much more “noticeable” because we dislike it. Warm grays and blue-grays are more to our liking

Similarly, Jim raised such a big issue with the printer because he was unhappy with the way the cover looked. If the printer had erred by printing the job too warm instead of too green, according to print specifications one error is as bad as the other, but I am sure Jim would not have been nearly as upset.

Ogden Rood wrote in the late nineteenth century: "The presence in a picture of a very moderate amount of a colour approaching bluish-green or emerald-green excites in most persons a feeling of disgust, and causes a work otherwise good to appear cold and hard--very cold and hard.”

Dan Margulis


Martin
 

On 19 Feb 2016, at 15:24, Jim Donovan jim@harrispublishing.com [COLORTHEORY] <COLORTHEORY@yahoogroups.com> wrote:

I knew my values were fine. Some cmyk values were around 64c 54m 57y 32k, 39c 33m 32y 19k

From a printer's POV I don't think these values are "fine".

They are neutrals that are entirely dependent on the printer maintaining perfect grey balance.

To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral.

A magazine's own repro dept would more than likely use even more aggressive GCR to save ink (and money) by using cmy values around 10% and nearer 80% k :)

--
Martin Orpen
Idea Digital Imaging Ltd


Michael Jahn
 

On Sat, Feb 20, 2016 at 9:29 AM, Martin g33kthug@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 
To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral.


Hi Martin,

Being a G7 kinda guy, I admit I am quite biased and find myself blurting things like "your fancy CMYK values for neutral grey may be quite pointless in my press environment"

and then share this chart to help explain "why"

https://flic.kr/p/aeMtiT

without **knowing the Lab values is of the substrate
without **knowing the Lab values solid primarys ( 100% C, 100% M 100% Y and 100% Y )
without **knowing the Lab values of the solid overprints ( 100%Y+M, 100%Y+C and 100%C+M )

Point being - it is difficult to 'predict' what the actually on press recipe to achieve a neutral grey using CMYK values.

As a designer, all one needs to do is create a tint that is 50C, 38Y and 38Y and place it next to a 50K tint, then tell the separator or printer to 'make them the same grey" - how they do that is entirely up to them I am afraid.

- and if you can't make a proof of what i just described above where they visually are neutral, then your proof is meaningless.

I have been sharing an example CMYK PDF that has SWOP tints since I made this PDF in 1997;

https://drive.google.com/file/d/0B7MTaA9sxe4xMjBjOThjYzUtOTg0My00YjQyLWE0MmItOTk4MzM5OGIxNWRl/view?usp=sharing


** knowing = measuring on the press sheet with a spectrophotometer and reading the Lab values 
for the few that are unfamiliar with the G7 Method - here is a link to a document that might help ( not the latest version, but online and downloadable;

http://files.idealliance.org/G7/PressOpGuide/Sheetfed_Offset/G7_Press_Guide.pdf

Hope this helps !

Respectfully,

Michael Jahn
1824 Garvin Avenue
Simi Valley, CA 93065
(805) 416 6946


Henry Davis
 

Unless I missed it, we don't know the context or the subject in the scene that had Jim's build. A global correction to hit this un- delicate build could ruin the scene. It would, however, be a forgiving build for a neutral graphic object. Since he said that the trouble was a "green cast" I suspect there were other areas that were greened as well.

Henry Davis

On Feb 20, 2016, at 12:29 PM, Martin g33kthug@gmail.com [COLORTHEORY] wrote:


On 19 Feb 2016, at 15:24, Jim Donovan jim@harrispublishing.com
[COLORTHEORY] <COLORTHEORY@yahoogroups.com> wrote:

I knew my values were fine. Some cmyk values were around 64c 54m
57y 32k, 39c 33m 32y 19k

From a printer's POV I don't think these values are "fine".

They are neutrals that are entirely dependent on the printer maintaining perfect grey balance.

To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral.

A magazine's own repro dept would more than likely use even more aggressive GCR to save ink (and money) by using cmy values around 10% and nearer 80% k :)

--
Martin Orpen


Henry Davis
 

Good builds and CMYK values in images ought to render as expected - regardless.

Henry Davis


On Feb 20, 2016, at 2:27 PM, Michael Jahn michaelejahn@... [COLORTHEORY] wrote:

 

On Sat, Feb 20, 2016 at 9:29 AM, Martin g33kthug@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 
To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral.


Hi Martin,

Being a G7 kinda guy, I admit I am quite biased and find myself blurting things like "your fancy CMYK values for neutral grey may be quite pointless in my press environment"

and then share this chart to help explain "why"

https://flic.kr/p/aeMtiT

without **knowing the Lab values is of the substrate
without **knowing the Lab values solid primarys ( 100% C, 100% M 100% Y and 100% Y )
without **knowing the Lab values of the solid overprints ( 100%Y+M, 100%Y+C and 100%C+M )

Point being - it is difficult to 'predict' what the actually on press recipe to achieve a neutral grey using CMYK values.

As a designer, all one needs to do is create a tint that is 50C, 38Y and 38Y and place it next to a 50K tint, then tell the separator or printer to 'make them the same grey" - how they do that is entirely up to them I am afraid.

- and if you can't make a proof of what i just described above where they visually are neutral, then your proof is meaningless.

I have been sharing an example CMYK PDF that has SWOP tints since I made this PDF in 1997;

https://drive.google.com/file/d/0B7MTaA9sxe4xMjBjOThjYzUtOTg0My00YjQyLWE0MmItOTk4MzM5OGIxNWRl/view?usp=sharing


** knowing = measuring on the press sheet with a spectrophotometer and reading the Lab values 
for the few that are unfamiliar with the G7 Method - here is a link to a document that might help ( not the latest version, but online and downloadable;

http://files.idealliance.org/G7/PressOpGuide/Sheetfed_Offset/G7_Press_Guide.pdf

Hope this helps !

Respectfully,

Michael Jahn


Michael Jahn
 



On Sat, Feb 20, 2016 at 11:53 AM, Henry Davis davishr@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

Good builds and CMYK values in images ought to render as expected - regardless.


Hi Henry,

Could not agree more.

If I provide an image with a CMYK build that should be neutral, then it is up to the prepress and printer to make it so...

what troubled me was what Martin Orpen shared;

"To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral."


1. Have no idea how one would get that CMYK in a submitted image without some some what aggressive GCR processing during RGB to CMYK conversion

2. Tend to think that grey would be somewhat warm ( if printed GRACoL )

Michael Jahn
Simi Valley, CA


Henry Davis
 

Yes, all sorts of CMYK builds can be neutral.  GRACoL, G7 or not.

Henry Davis

On Feb 20, 2016, at 7:59 PM, Michael Jahn michaelejahn@... [COLORTHEORY] wrote:

 



On Sat, Feb 20, 2016 at 11:53 AM, Henry Davis davishr@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

Good builds and CMYK values in images ought to render as expected - regardless.


Hi Henry,

Could not agree more.

If I provide an image with a CMYK build that should be neutral, then it is up to the prepress and printer to make it so...

what troubled me was what Martin Orpen shared;

"To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral."


1. Have no idea how one would get that CMYK in a submitted image without some some what aggressive GCR processing during RGB to CMYK conversion

2. Tend to think that grey would be somewhat warm ( if printed GRACoL )

Michael Jahn


Martin
 

On 20 Feb 2016, at 19:53, Henry Davis davishr@bellsouth.net [COLORTHEORY] <COLORTHEORY@yahoogroups.com> wrote:

Good builds and CMYK values in images ought to render as expected - regardless.

They won't though.

A cmy neutral will render differently on every page of a magazine.

If your images depend on accurate, repeatable neutrals -- most common obvious failures are black & white double page spreads that don't match -- then you soon realise that predominantly cmy neutrals will not render as expected.

Sure you can put all the blame on the printer -- but keep in mind that no pro repro facility would send the OP's CMYK values to print and expect them to print as reliable neutrals.

--
Martin Orpen
Idea Digital Imaging Ltd


Henry Davis
 

Had Jim's neutral objects in the scene printed as "near" neutral instead of having a green cast along with everything else I doubt that he would have had much of a complaint.

He gave values from two areas:

"I knew my values were fine. Some cmyk values were around 64c 54m 57y 32k, 39c 33m 32y 19k"

It could be that this particular image didn't lend itself to a heavy black generation.  Besides, these kinds of values have worked consistently with this printer without such a train wreck.

Martin, your last comment is interesting.  Pro repro facilities often send similar CMYK values to print, and expect them to print within reason.  Neutrals are not the only case, pastels and other delicate colors can be rendered within reason.  My experience with magazine runs lowered my expectations long ago - but sometimes the results are totally unreasonable.  In those cases it's because the printer has completely lost it.  This was the case for the situation we're discussing - the printer screwed up and admitted it.  I appreciate your consideration for heading off worst-case situations - it's a good practice when there's a high probability for a screw up.

But . . .

Jim's experience and procedures have not disappointed him in 20 years of working with this printer.  His methods have worked for a long time and have met his expectations - yet you claim that they shouldn't have.  That is interesting.

Henry Davis


On Feb 21, 2016, at 8:45 AM, Martin g33kthug@... [COLORTHEORY] wrote:

 


> On 20 Feb 2016, at 19:53, Henry Davis davishr@... [COLORTHEORY] <COLORTHEORY@...> wrote:
>
> Good builds and CMYK values in images ought to render as expected - regardless.

They won't though.

A cmy neutral will render differently on every page of a magazine.

If your images depend on accurate, repeatable neutrals -- most common obvious failures are black & white double page spreads that don't match -- then you soon realise that predominantly cmy neutrals will not render as expected.

Sure you can put all the blame on the printer -- but keep in mind that no pro repro facility would send the OP's CMYK values to print and expect them to print as reliable neutrals.

--
Martin Orpen


Dan Margulis
 


Martin Orpen writes,

If your images depend on accurate, repeatable neutrals -- most common obvious failures are black & white double page spreads that don't match -- then you soon realise that predominantly cmy neutrals will not render as expected.

Correct as stated, but limited by the first phrase: IF YOUR IMAGES DEPEND ON ACCURATE, REPEATABLE NEUTRALS. Most don’t, and we have no reason to suppose that the OP’s cover did. Granted that the printer has already admitted fault, putting in more black and less CMY is a poor suggestion.

Sure you can put all the blame on the printer -- but keep in mind that no pro repro facility would send the OP's CMYK values to print and expect them to print as reliable neutrals.

On the contrary, no knowledgeable prepress person would (except in cases like the above, where control of neutrality is ABSOLUTELY CRITICAL) think of inviting disaster by loading up a normal sep with extra GCR, particularly with a printer whose QC is suspect. Too many people have gotten burned by falling for a printer’s cock-and-bull story about how more black is the way to go (besides saving them money on ink).

SWOP standards call for no more than 2 points variance in a midtone. So even if the OP supplies 50c40m40y with no black at all (or whatever the current recommendation for CMY balance is is), the printer has to be out of spec to make it perceptibly non-gray. But any logical separation algorithm will anchor this with 30 or 40k. With that much black ink, if the printer can’t hold neutrality he’s twenty miles off any standard and the client should demand that the the “work” be redone, or not pay for it if time does not permit a remake.  

Putting in more black ink and less CMY eliminates neutral shifting at the very high cost of risking a dark and muddy appearance if the printer mishandles the black even slightly. Gray shifting is a bad thing but many jobs are acceptable even so. Errors in magenta inking are more consequential than in CY and still the printer can often get away with it. Errors in even a *standard* black can be just as bad. With a super-heavy black even a small error ruins the job.

Consequently, to prescribe a massive infusion of black in the OP’s case is to prescribe morphine to a patient who has a headache. It definitely *will* cure the headache, no doubt about it, but there are less risky ways to do so.

In the case cited—a grayscale image printed with CMYK—of course I agree that the ratio of K to CMY should be sharply increased, as with any other image where the control of neutrality is ABSOLUTELY ESSENTIAL, silver jewelry being an example. The risk/reward calculation is very different than from a normal color photo.

Dan Margulis


Henry Davis
 

Hi Michael,

The values posted have a shot at being near enough to neutral:

64c 54m 57y 32k
39c 33m 32y 19k

Plus, I don't think Jim was expecting a measurably exact neutral outcome.  I'm guessing that within an image, a near to neutral object wouldn't have been offensive.

My vision seems to play tricks with things like this anyhow.  If I think that car, for example, has a black vinyl top I'm pretty sure I ignore any deviations until they become impossible to ignore.  

I agree with Martin that there needs to be extra insurance when preparing images for magazine.  However, aggressive GCR or Heavy black generation can ruin some images.

Henry Davis 

On Feb 20, 2016, at 7:59 PM, Michael Jahn michaelejahn@... [COLORTHEORY] wrote:

 



On Sat, Feb 20, 2016 at 11:53 AM, Henry Davis davishr@... [COLORTHEORY] <COLORTHEORY@...> wrote:
 

Good builds and CMYK values in images ought to render as expected - regardless.


Hi Henry,

Could not agree more.

If I provide an image with a CMYK build that should be neutral, then it is up to the prepress and printer to make it so...

what troubled me was what Martin Orpen shared;

"To ensure your neutrals stay neutral you should provide something like c27 m24 y25 k70 for your darker neutral."


1. Have no idea how one would get that CMYK in a submitted image without some some what aggressive GCR processing during RGB to CMYK conversion

2. Tend to think that grey would be somewhat warm ( if printed GRACoL )