8 replies to this topic

[The Doomed Mapper]

Hello out there, purveyors of all things maps!

I have a question about about overprinting and its potential use in mapping while working in Illustrator CS3. Traditionally, when creating the linework for roads, we would put the line "fill" in one layer and the line "casing" in another. However, for some of maps my company produces, I notice that overprinting has been turned on for certain layers, specifically those relating to road linework (in these cases, the the Overprint Stroke box in the attribute panel is ticked). The reason why this is an issue is that when we finally print the maps, we get strange results, with the white "fill" not printing at all. For example, instead of getting state roads in the attached image to look like (a), we end up with an image that looks like (. (Please note that the respective layers are set to print and displayed in the final product).

My understanding of overprinting is somewhat nebulous. From what I can gather, it ensures that the blacks contain in different images blend together properly, printing first the CMY colors and then the black over these. However, if this were the case, why would one need to turn on this feature for a white stroke with a 0 K value (such as those dislayed within the picture?). Does not the fact that we have a complex layering scheme render the need for overprinting to be somewhat useless?

Any help would be greatly appreciated!

Attached Files

•  Bad.png   39.31K   55 downloads
•  Good.png   138.89K   59 downloads

[DaveB]

Overprinting means one ink is printed over or on top of a previous layer of ink. It's mostly used when you have darker colored type or lines on top of lighter color fills. It's done to prevent slight mis-registration revealing white gaps between the darker color and the lighter color.
Basically in the example you showed you're telling the "white" ink to print on top of the green, which of course lets the green show through.

[Unit Seven]

What Dave said is correct. Overprint fill or stroke is an object level setting that uses the objects ink values over (rather than instead of) the objects below. Don't think of overprint effecting the colour as a whole but as working on each cmyk component of the colour.

You pretty much always print black as 100%k without any cyan, magenta, or yellow and overprint it. If you are talking large bold objects you may knock it out (like a page background as you can see the objects through the black sometimes) or add some Cyan or Magenta to create a rich black.

White should never really be set to overprint and there is a preflight check in Acrobat to detect white objects set to overprint. It is not overprinting the white but is over printing each component of the white. Because each of them are 0 there is nothing to overprint so it disappears. Having said that we did use it once to create masks around text objects but have the text objects invisible in the final product as they were added on another layer via a different process.

We often also set our hydro linework to 100% cyan overprint to make it blend with the map base a bit more.

Another trick is to set a stroke around the text to 1% black overprint and this will make any black component behind the text disappear but as there is no cyan or magenta to overprint it will keep these components so you don't end up with an obtrusive white halo around your text—road casings or dark relief is the perfect example of this. This is much more efficient than trying to create thousands of variable depth masks in ArcMap terminology, table masking in Microstation, or clipping masks in Postscript/Illustrator.

It can sometimes be used for multiply type if the colour is getting up towards 100% of the ink in question effect without flattening of the file when it goes to press as overprint is supported by postscript but transparency bending modes are not—in this case we use it to show road casings at 50% black, buildings in a similar way so you can see the parcel or land colour behind them. See attached pdf which a created a few months back for one of our new staff. Be careful and get your head around how this works across different plates and colour percentages though as it can give unexpected results.

...and Dave I know this is a question you probably can't say anything (NDAs etc) but just to keep the pressure on ESRI when you going to bring overprinting into ArcMap? This is one of my biggest gripes with ArcMap and have logged with our Local distributor and see it has been previously logged as a bug with ESRI—though I guess it's more of a lacking feature than a bug.

Cheers,

Sam.

Attached Files

•  Overprint_Examples.pdf   588.8K   87 downloads

[Kevin McManigal]

 With_OverP.jpg   411.29K   89 downloadsHowdy,

We just went though the overprinting issue with the proofs of our maps. Roads in black or in shades of grey came back semi-transparent, showing the background features beneath. This is because the K ink was printed over all the C, M, and Y. I found that in Illustrator, under the View menu, the Overprint Preview option will show you what you’re going to get from a four color press.

To get your road fill to look proper, just uncheck the overprint fill box (or stroke if that is its style) in the attributes menu, and take a look at the overprint preview. This will cause the white sections of the roads to "knock-out" any underlying color so true white can be rendered.

Check out the "With OP" and "Without OP" images.

Hope this helps,

Kevin

Attached Files

•  Without_OverP.jpg   413.9K   58 downloads

[Rick Dey]

The whole process of applying overprinting, as others have said, relates to the offset printing process and to some degree also to digital printing. You could spend a substantial amount of time looking at the ramifications. In many cases having lines knockout the underlying colors on the map (not overprint) is unnecessary in a printed product (depending on the scale). The user just isn't going to perceive the color difference as a line passes through one underlying color fill to another. There are inherent limitations in printing ink on a media as unstable as paper and adding a knockout to complex shapes may well cause gutters that are more noticeable than the color changes that occur with overprints.

Having said all that though, I can not stress the importance of discussing with your printer overprints and trapping. All the best design with overprints can be quickly negated by an overzealous (or just plain well meaning) pre-press operator clicking the wrong button. If you are planning to print a project, involve your printer at the very beginning of the project while still designing and setting your specs. Far too often the printer is an afterthought after the entire map is finished, opening you up to all kinds of "Cartastrophies".

[The Doomed Mapper]

Wow, you folks really outdid yourselves with your discussion of overprinting here; I have a pretty good understand of the underlaying concept and when it may or may not be useful to use this feature.

Rick Dey: I agree with you; I talked with our printer contacts and she essentally said that it is not necessery, at least for the way that we accomplish our printing (which is sent out of house). She did mention that it would make sense (and this is what I suspected) to set overprinting for Black text and Black lines, which also makes sense to me.

K-Map: Thank you so much for pointing out the fact that there is an overprinting preview in Illustrator. I was looking around for it in the help file, and for the life of me could not find it in that method. Thank you very much

Dave B & Unit Seven: Thanks for the reference images, as well as explaining exactly why the white lines were "dissapearing." on my map. I knew that overprinting was the culprit but could not understand WHY the white was disappearing (in depth answer such as this are the manner in which is the way that I most effectively learn and was having some difficulty finding online). You mentioned that there is a preflight check for overprinting in acrobat: do you happen to know where it is? (I want to pass this information on to the parties involved. If it's too much trouble to point out, no worries, I'm not lazy and can figure it out myself! )

So kudos to all of you folks. By the way, I figured out why the files had such strange overprinting attributes had been set on these maps to start with, and it might be worthy of starting it up as a new thread. Apparently, many of my companies files were made many years ago in a "younger"version of Illustrator. At first I thought that the strange overprinting that had been turned on was there for some reason that I was not aware of (being new to the field in a professional sense). However, we have realized that there is no reason for overprinting to be turned on in these cases, and it has become somewhat systematic. We suspect that there is an issue with the file conversion process as we update the older files to CS2/CS3 which may be turning on overprinting for objects. Has anyone else seen this type of behavior?

Again, thanks to everyone for your help, you guys (and gals!) are great!

[Unit Seven]

K-Map: Thank you so much for pointing out the fact that there is an overprinting preview in Illustrator. I was looking around for it in the help file, and for the life of me could not find it in that method. Thank you very much

You mentioned that there is a preflight check for overprinting in acrobat: do you happen to know where it is?

Glad to help.

Preflighting has to be Acrobat Pro—I think it was only introduced in version 8 though. Has a lot of other useful tests as well.
Acrobat > Advanced > Preflight.

Never heard of them changing like that but I guess anything is possible. A lot of our issues have been objects that were originally black (or some other colour that was meant to overprint) and has since been changed to another colour but the overprint setting hasn't been changed appropriately. Note that a lot of software (InDesign and prob Illustrator) will set 100% black objects to overprint automatically.

Cheers,

Sam.

[natcase]

Where we have seen consistent trouble is in translation from Freehand to Illustrator: not all blacks overprint as they should, an occasional overprinting-white slips through, and often Freehand black (which had a default RGB definition, I believe) turns into a "rich black".

The best way I've found to check on all of these is in Acrobat: Advanced>Print Production>Output Preview. This also lets you see if spot colors got into the mix somehow (often in client-supplied content, but not always). You turn off the black ink layer, and you can (1) see where black type is not overprinting and (2) see where there is still dark-gray type, indicating a rich black.

[MichaelG]

...and Dave I know this is a question you probably can't say anything (NDAs etc) but just to keep the pressure on ESRI when you going to bring overprinting into ArcMap? This is one of my biggest gripes with ArcMap and have logged with our Local distributor and see it has been previously logged as a bug with ESRI—though I guess it's more of a lacking feature than a bug.

Cheers,

Sam.

Greetings.

If you are and ESRI user and would like to follow status of and/or advocate for adding overprint definition and export support to ArcMap, the offical ESRI tracking number is:
NIM002398 - Add support for overprint / knockout settings

Peas,
Michael