Tag Archives: Transparency

The Evil EPS

5 Feb

Now why do we call the EPS file format, more formally referred to as encapsulated postscript, evil? Because, with EPS, we are never quite sure what we are going to get. The format has less than consistent support for transparency advanced clipping masks and spot color. In addition, certain export settings resemble to the old style “flattened” version of digital art, such as the PDFX1/a.

Let’s take a look at how wacky this can get by revisiting our sample art from a previous posting. Notice that the same spot color is used on several different objects. Also, take note of the white portion of the BPI logo; it employs a feature called a drop shadow which overlays the custom Reflex Blue spot color.

Now, let’s make an EPS from Adobe Illustrator with the export compatibility set for CS3. First, let’s take a look at our initial result (Banner_Art_eps).

Banner_Art_eps

Notice that the layer structure is intact. It is unchanged from the Illustrator source file. Now, let’s examine the art in outline view (see Banner_Art_eps_Outlines).

Banner Art_Outlines

Notice the complete absence of slices. As you can see in the Banner_Art_eps_LiveScripts screenshot below, the Illustrator scripts for fills and drop shadows are still active. A number of newer RIPs (Raster Image Processors) can read these appearance scripts and correctly interpret them.

Banner_Art_eps_LiveScripts

So where’s the problem? Let’s toss a bomb into the mix. Let’s place the same art in InDesign and export to EPS and use the highest quality settings available (see InDesign_Export_eps screenshot).

InDesign_Export_eps

Let’s take a look at the results in outline view (see InDesign_eps_Outlines).

InDesign_eps_Outlines

Instead of a digital file made up of vector objects and live scripts, we now have a mixed bag of vector and raster objects. We also have a pretty obvious slicing error. But wait, it gets worse! Take a look at the color values in the logo (see Color_Error1 screenshot below).

Color_Error1

That’s not the only potential color problem. Take a look at the cmyk values of the image slice in the logo (see Color_Error2 at left). That particular slice butts up to the vector object with the Color_Error_2original spot color value (see Color_Error3). Now things are getting really complicated. In the large format world, a RIPColor_Error_3 calculates color values and it usually calculates a spot color, vector object in LAB. However, a raster image, like the one in Color_Error3, will be calculated in cmyk. Print this file and you will have two very different shades of blue piled next to each other. Furthermore, print this file and you better be ready to do this job over.

Frankly, the future of the EPS file format is solidly in the past. EPS is rapidly becoming an outdated file format which is being replaced by PDF just like PostScript itself is also being phased out and replaced by PDF. Check out what Dov Isaacs from Adobe said in a discussion on a Print Planet forum about the future of PostScript:

“ …Adobe will continue to support EPS as a legacy graphics format for import of non-color managed, opaque graphical data into Adobe applications (such as InDesign and Illustrator). Although we certainly do not recommend that new graphical content be stored in EPS format (except to satisfy the need to import data into page layout programs that aren’t quite PDF-centric), our user base should feel comfortable that there is no need to worry about a need to convert their very sizable libraries of EPS-based graphic assets.”

When a principal scientist with Adobe employs the phrase “legacy graphics format,” it’s time to move on.

Flattening and transparency are pretty confusing subjects. If you’re still curious, or just plain lost in the woods over flattening and transparency, check out the online tutorial below for more information.

http://vector.tutsplus.com/articles/help-with-selling-vector-stock-in-eps10-format

Why Slices and Spot Colors Don’t Mix

4 Dec

One of the many stumbling blocks of print design is the interaction of transparency and spot color.  It’s a rather demanding subject and impossible to cover completely in a single blog entry.  So, let’s confine our discussion to the realm of the PDF/X1a.  And, just to keep things simple, we’ll use the same BPI banner art from the previous blog posting.

First, let’s take a look at the Spot_Color screenshot below.  As you can see, the BPI logo, headline and web address all share the same value, a variation of the legacy version of Pantone Reflex Blue-Coated spot color.  Notice that the spot color objects are uniformly close to the top of the stacking order with only solid objects like the white BPI and green leaf with a solid white stroke above them.

Now, lets take another look at the PDFX/1a version of this art (screenshots Spot_Color_PDF and Spot_Color_PDF_Outlines). Despite the lack of transparency. The automated PDF engine has created several slices and clipping masks. But because there are no interactive transparent objects, the slices still retain their original color value of PANTONE Reflex Blue 2X CVC 2.

    

Now, let’s screw this up. Let’s add a drop shadow to the white portion of the BPI logo. We’ll use the default drop shadow values (see Drop_Shadow screenshot below).

Please take note of the transparency values of Mode and Opacity. Next, we’ll save this art as a PDF version X/1a . Now let’s take a look at the results, see the Missing screenshot below.

Our drop shadow appears to have vanished and a few chunks of the logo have changed colors to the background blue. But wait, there’s more. The bpi has shifted away from a true white of 0 cyan, 0 magenta, 0 yellow, 0 black to something a little different – see Color_Shift screenshot.

If you think this is disappointing, take a look at how Acrobat views the same art (Acrobat screenshot). If you tried to print this file in a conventional RIP, the only thing you could count on is NOT getting what you wanted.

So how do you avoid this. Either avoid overlaying any transparent elements over objects with spot color or employ a different Acrobat preset. Just for example, here’s what the High Quality Print preset looks like – see HiQual_Preview screenshot. At last, everything looks exactly like it’s supposed to.

But the big question is, will the new PDF print correctly? Only your service provider can answer that question. And that’s going to depend on the capabilities of their RIP and print devices. If you have any doubts, call and ask. Everybody likes getting things right the first time.

Constructing a Bullet-Proof Digital File with Illustrator

17 Jul

Making your art work varies from platform to platform.  Although there are commonalities (we’ll review them in a little bit), workflow practices vary depending on the application. In order to keep the size of this entry small enough to keep us out of trouble with our blog-meister, let’s limit this discussion to Adobe Illustrator.  Illustrator is the vehicle of choice for most large format service providers in the creation of print files.

Let’s take a minute to review some of the tips from previous blog posts for successful color management:

  1. Complete all your image work first.
  2. Make sure all of your images are in the appropriate color family for your end product (RGB for web and photo or CMYK for offset printing and large format work reproduction).
  3. All images should be in the same profile.  Examples are: sRGB IEC1966-2.1 for web; Adobe RGB 1998 for photo and Durst/Lambda or LightJet; US Web Coated (SWOP) v2 or Coated Gracol 2006 for most North American offset printing.
  4. Conserve your assets! Make sure you still have unaltered client originals and your multi-layer Photoshop files.

Now, let’s create our working file in Illustrator. The first thing is to check your document color space (File > Document Color Mode > CMYK). Why is CMYK recommended if you’re working in RGB? As we talked about in a previous blog-posting, conversion of postscript values in vector art from CMYK to RGB is a reliable method for maintaining a similar appearance across the spectrum of web and print. It is not reliable in the other direction. (screenshots below in this order: first, CMYK_Black; second, Change2_RGB_Black; and finally, ChangeBack2CMYK).

We will now assign the ICC profile. What we’re going to do is set up Illustrator in such a way as to prevent unintended color transformations (as demonstrated in the previous screenshots). Go to the top menu bar and select Edit > Assign Profile. This will open the Assign Profile dialog box. Check the top radial button, “Don’t Color Manage This Document.” This will prevent Illustrator from changing the color values of any files you link to (“Place” in the File Drop Down Menu) or paste into your document. If you leave Illustrator color management in its default profile (for CMYK that’s generally in US SWOPv2 in North America), each time you paste art from other files into your working file you may, depending on your version of Illustrator, experience unwanted color transformations when you paste or place and embed art into your working file.

Finally, let’s set the value for the Tranperancy Preset. The Transperancy Preset (sometimes referred to as the “flattener preset”) controls the pixel values for any raster objects Illustrator creates from effects like drop shadows, outer glows, and blurs. You want to go to the “Preset:” drop down menu inside the Transparency section of the Document Setup dialog box (File > Document Setup or Alt/Opt+Com/Ctrl+P). You have four options: High Resolution, Medium Resolution, Low Resolution, and Custom. High Resolution assigns pixel values of 300 and is considered the standard for offset printing. Medium Resolution assigns pixel values of 150 and is considered the standard for large format reproduction. Low Resolution creates raster objects with a value of 72 pixels per inch. Low Resolution is considered acceptable for screen printing or web graphics. Remember, these values do not affect images you link to or embed in your art. You can resample your images when you save as a PDF. We’ll delve into that in a later blog posting.

Before you construct your art, you should consider a couple of warnings. First, objects with transperancy effects interact with each other. Be sure you’re fully aware of the capabilities of your service provider before you stack drop shadows, blends, or other effects on top of each other. (Of course, if you’re using BPI, you don’t have to worry about that.) Second, when designing for offset printing, avoid overlaying transparent effects or objects on top of spot colors. Technically, a spot color is supposed to print separate from the normal 4 colors. When RIPS attempt to create a flattened file for color separation, they create image-blocks (sometimes called slices) of raster objects (hopefully you remember the difference between raster and vector) which may vary in appearance from the objects that have a solid spot color value.

Next Time: Let’s talk about InDesign.

PS: Perhaps some of this seems a bit confusing. If you’ve never visited this blog before, perhaps you should visit some of our other postings: “Why What you See Is Not Always What You Get!”; “Basketballs, Meatloafs and Frisbees, Oh My!”; and, “Those Pesky Profiles”.

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