Two very important processes that take
place in prepress are trapping and ripping.
Don't we have interesting words in printing.
Now trapping is performed in order to
compensate for any possible mis- registration on press.
So, when is trapping required?
Well, when you have objects touching each other that don't have color in common.
So, here I have a yellow word TRAP and it's placed on top of this cyan rectangle.
So, there is no color in common.
These are two separate plates, two separates inks.
What if the press were out of register?
This is exaggerated for a dramatic effect to give you an
idea to give you an idea of why we perform TRAP.
But you can see where the yellow and the blue
overlap, it makes for sort of an ugly combination of green.
But where we see the paper shining through,
where we have the white gaps, that's really obvious.
Then again, this is exaggerated.
Presses are very tightly controlled these day.
You're never going to
see anything like this. So what is a TRAP?
And again, this is exaggerated as well.
It's the creation of a combination of those colors
so now there is a color in common so is
the press is a little bit off, you're not
going to see that ugly white paper which is really obvious.
And then again the TRAPs never going to be this heavy, but what it's accomplished is
combining those two colors the cyan and the
yellow so you'll never see that paper leak through.
Now this is what a TRAP really looks like see you
barely notice it.
This again has been exaggerated for dramatic effect.
But this is a complicated situation.
And this is why we don't perform TRAPs manually anymore,
we don't create artwork in illustrator and carve these things out.
We just hand this job off to the RIP.
And it's very sophisticated and knows how to handle complex situations like this.
Going from left to right, you can see that the color of
the text doesn't change but that gradient goes from a dark blue to
a light blue.
So at the far left, the luminosity, the lightness
of the T is actually lighter than that gradient.
So the dark area always defines the shape.
So in this case again exaggerated.
The color of the T has been combined
with the colors of that grading in that location.
And the shape of the T has been expanded so that we have common colors there, But
as you go across, the color of the
text stays the same but the gradient gets lighter.
While there at the far right, you can see, that instead of spreading the
type color out, the grading color is choked underneath, That's the term for it.
On the left we're spreading the T.
On the right we're choking so that, that gradient falls inside the shape.
Because again, the darker color defines the shape of it.
If you sort of squint at it you get a little better idea of what's going on.
Aren't you glad you don't have to create these and
in prepress we're glad we don't have to do this anymore.
We can just hand
the job off to the RIP and it does this very sophisticated trapping for us.
So what is a RIP?
Ripping sounds like a bad thing, but trust me if the printer
says, hey, we successfully ripped your job, this is a very good thing.
It's translating your files for imaging. What do I mean by translating.
Well what you've created on screen gets converted into a language that
platesetter, or an image setter or an ink jet large format printer understands.
RIP stands for raster image processor.
So it converts your page content actually a bitmap, to tiny, tiny pixels.
For example a platesetter that's 2,400 pixels per inch,
that's how tiny those little pixels are going to be.
And it really is a literal road map
for the platesetter or for the proofing device.
Now Trapping as I mentioned is usually performed in
the RIP, so these things happen together, they're very interrelated.
Now
RIPs from different vendors use different workflows.
So different printers may have to handle your file in different ways
in order to make sure that they work on their particular RIP.
So here's an original design, there's just a picture and some
text, so let's see what happens When it hits the RIP.
One of the things the RIP does is create
as I said t his roadmap for the imaging device.
So here's the cian plate.
It's going to read across there and it's going to generate
pixels which uses that to guide that laser that's going to burn that plate.
And it's going to create the magenta.
The yellow and finally the black.
Now, you notice there's no half tone pattern in the black.
That's because it's black text.
It's just solid, but where we have the
image it's going to be broken into half tones.
And that's how we get all those colors on a press.
But this is what a RIP does.
It takes that continuous tone or vector original.
And then it turns it
into something that it can feed to that plate setter or that proofing device
and that's the road map that that device follows as it images your job.