illus trapping and overprint

[Mark]

I normally trap in our rips trapping software. I have to trap in illustrator file and save out a pdf for customer with traps.

How the heck do i do trapping and overprinting in illustrator CS4, In the file rather than printing and setting it there. Am i missing something because transparency multiply isn't giving me proper overprint of black. Its showing a darker color underneath in sep preview when i turn off black.

Thanks

[maynardsayswhat]

Multiply does exactly that, multiplies the color with the overlay. Great for making more realistic shadows etc., but otherwise tricky to output without a RIP. Transparency modes shouldn't be used for trapping normally.

Is the file continuous tone or pure vectors? Trapping vector objects native in Illustrator is normally done with overprinted/choked strokes and can involve a certain amount of redrawing shapes either by hand or with Pathfinder. I don't know many offset pre-press folks who will will do this by hand. It's far more common in my experience in the screen print world.

Also be sure you're in preview mode with overprints turned on. I often forget to set this view mode myself and it can lead to a lot of head-scratching.

[oxburger]

You can also try using Illustrators trapping. I think everything has to be grouped, but once it is grouped select:

Effect > Pathfinder > Trap

and select your parameters.

[DCurry]

Great idea, Ox. Didn't know that was there in Illy.

Yet a third option is to use InDesign's built-in trapping. You'd have to save the Illy file as .ai (not EPS) and place it into an InDesign file. Open up the Trap Presets palette (Window>Output>Trap Presets) and set things as you want. To make a trapped PDF, you can't do a direct export. Instead, you have to print to a PostScript file and in the Output tab make sure you choose Color: In-Rip Separations and Trapping: Application Built-In. Now take the resulting PostScript file and run it thru Distiller to make your PDF.

Make sure Overprint Preview is turned on in Acrobat when you look at your PDF to check it out.

[Mark]

Thanks, i was hoping it would be easier. Having to manually trap is a pain.
Is there a plug in for better trapping in illustrator?
Or perhaps a Acrobat trapping plug in?

[Chief_1975]

Use "Darken" not multiply which basically does the same as "overprint" although you can see the result without having to have "view with overprint preview" switched on.

There is certain amount of fear about using transparencies effects for trapping however in general I find that most printers have got RIPs now that will handle them ok, having said best to check with the printer first.

Trapping vectors is fairly easy with using strokes or duplicating up the objects, turn to zero fill, reduce the size by trap amount, send to the back, set front object to darken.

[prepressbb]

I don't know many offset pre-press folks who will will do this by hand. It's far more common in my experience in the screen print world.

Well thats true, you'll mostly find alot of manual trapping with advance flexo shops. I do it everyday at my plant, and we use Illustrator, theres nothing really to it. The most difficult part, is actually knowing what you want to achieve and setting parameters(minimal and maximum trap). But as far as manually drawing shapes, thats not really necessary unless needed. the pathfinder tool is really handy when it comes to paths and shapes. And i could go on all day but i wont. ITS NOT THAT HARD.

[prepressbb]

I normally trap in our rips trapping software. I have to trap in illustrator file and save out a pdf for customer with traps.

How the heck do i do trapping and overprinting in illustrator CS4, In the file rather than printing and setting it there. Am i missing something because transparency multiply isn't giving me proper overprint of black. Its showing a darker color underneath in sep preview when i turn off black.

Thanks

In your attributes window you could use the overprint features there. The actual overprints when using that method only shows in overprint preview.

[Mark]

I guess i missed the attributes overprint, my mistake.
Now i'm looking for a plug in for illustrator to make trapping less of a pain and faster.

Anyone using EskoArtworks Powertrapper?

[prepressbb]

Now i'm looking for a plug in for illustrator to make trapping less of a pain and faster.

Anyone using EskoArtworks Powertrapper?

Yea, we use Powertrapper, its quite nice and user friendly i got to say (but as like everything else in printing, its great with the less complicated stuff, and it doesn't trap images, thats something that i was told they are working on for the next upgrade. But yea it works.
If you want i think theres a trial version of the plugin on esko website that you could try.