Tag Archives: RGB

Constructing a Bullet-Proof Digital File with InDesign

9 Oct

The InDesign workspace is a bit trickier to manage for consistent color than Illustrator. Unlike Illustrator, InDesign was created for the purpose of managing large multi-page documents such as magazines, newsletters, and books. As a digital layout program, it is obviously not limited to multi-page design. Several graphic designers use InDesign for business cards, brochures, posters, large format display, and web content.

When creating a new document, you should pick the color settings that best match the method of reproduction. For offset printing, pick CMYK; for photographic reproduction (Durst, LightJet, and Lambda) or web/internet, pick RGB. To access or change the color settings for your document, go to the top of the window in InDesign and select Edit > Transparency Blend Space. Then pick Document RGB or Document CMYK.

Next, set the appropriate Transparency Flattener Preset (Edit > Transparency Flattener Presets…). There are only three options: low, medium, and high resolution. (See TF_Presets screenshot.) The low preset is intended for web and silkscreen printing, medium is intended for large format reproduction, and high is intended for high quality offset printing.

Finally, check the Color Settings of your document (Edit > Color Settings). (See Color Settings screenshot.) Most of the work BPI receives is designed for offset printing, so we use the default North America Prepress 2 settings. Notice the field CMYK: Preserve Numbers (Ignore Linked Profiles) setting in the Color Management Profiles field. By employing this setting, InDesign is prevented from performing a color transformation on art opened on this workstation or pasted into this document. Otherwise, art that has a different CMYK profile would have the CMYK values shifted to fit within the ICC model for US Web Coated (SWOP) 2. If you’re new to this blog, just trust us–an uncontrolled color transformation is a bad gamble.

Note the check boxes underneath Color Management Policies. When InDesign detects a missing or mismatched ICC profile, the Profile or Policy Mismatch dialog box will open. By default, the “Leave the document as is” option is selected. This is the option BPI recommends. Remember, unmanaged color transformation = bad gambling.

Now, 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; etc…)
  4. Conserve your assets! Make sure you still have (or have access to) unaltered client originals and your multi-layer Photoshop files.

Before you construct your art, you should consider a couple of additional 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, glows 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 seperation, they create image-blocks (sometimes called slices) of raster objects which will vary in color value and appearance from the objects that have a solid spot color value.

Finally, let’s talk about some of the export options for PDF in InDesign. When you elect to export as PDF, the first thing you get is the Export Adobe PDF dialog box. (See Export PDF screenshot.) BPI generally recommends the High Quality Print preset as a starting point. For enhanced transparency support, we suggest a using a compatibility setting of Acrobat 6. (See Export PDF Modified screenshot.) Also, we suggest employing ZIP compression (see Export Compression screenshot), setting the Output Color options to “No Color Conversion,” and setting the Profile Inclusion Poilicy to Include Tagged Source Profiles. Remember, if all your image work has been converted to the appropriate color space and ICC profile, you don’t need InDesign to perform color conversion. We recommend ZIP compression to avoid piling jpeg compression on top of jpeg compression, which can result in an unattractive image appearance. Also, including the tagged source profiles lets your print provider know what image environment the art is intended for and doesn’t change the color values of your file at all.

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

Advertisements

Diving Deep in Image Management

27 Mar

Our workflow begins with client supplied images and proceeds along separate parallel tracks : one for CMYK and one for RGB. For the sake of argument, let’s assume you have several unaltered digital photos to manage. And, just to narrow the focus a little more, let’s confine the purpose of this entry to print production, not web or internet. Therefore, the beginning image management section of the RGB workflow is the appropriate place to start.

As you may have noticed, most RGB images have an embedded profile of sRGB IEC61966-2.1. Unfortunately, this is not a trustworthy production color space. It’s fine for web, but if you’re going to design for print you should convert all your images to Adobe RGB (1998). Why? Some RIPs have an out-dated version of this profile and will image poorly if you print directly from sRGB IEC61966-2.1. Furthermore, many higher-end digital cameras have a color space that is described as sRGB IEC61966-2.1 (it’s what shows up in the profile information in Photoshop) but is actually larger and closer too Adobe RGB (1998). Predictable color is dependent on having a common reference for conversion and output. Some service providers recommend the profile sRGB, so far, we have more predictable and reliable results with Adobe RGB (1998).

To convert your images in Photoshop, go to the top menu bar and select Edit > Convert to Profile. Make sure to check the “Use Black Point Compensation” and “Use Dither” boxes in the “Conversion Options” of the dialog box. This will mitigate any posterizing of your image. And finally, don’t hit “Okay” without clicking the preview button a few times. There is one caveat concerning “Black Point Compensation”; if your image has little to no shadow content you might want to uncheck this option. That’s what the Preview option is for. Preview is your chance to see if you are going to have any issues with your color conversion. Finally, save your converted files as new Photoshop files. You never know when you might want to go back to your original customer provided files. Sometimes the client needs them because they’ve lost track of their original images. Occasionally, there’s a concern over the appearance of the printed piece and your client will want to examine your work against what was provided. CYA, conserve your assets.

You can use Photoshop to convert all your files as a batch action. Photoshop batch processing, actions and droplets can save you a lot of time. When we employ these features, we always open the new files and compare the appearances to the original files. A blind process does not always yield the best results. We’ll talk more about the dangers of blind processing when we cover PDF creation.

Now that all your images are in a common color profile perform your edits (clone brush retouch, color range adjustments, addition of other elements, sizing and cropping). You’ll want to save these as multilayer Photoshop files. Do your alterations in a non-destructive manner with layer copies, masks and adjustment layers. You never know when you’ll have to go back and tweak something for a current or future project. Once all edits have been finished, save copies of your files as flattened TIF’s. DO NOT save over or discard your multilayer Photoshop files. That is the digital equivalent of painting yourself into a corner. Work that way and one of these days you’ll be sorry.

You may have heard about a loss-less version of jpeg called JPEG 2000. The problem with that format is not every RIP can process it. It’s no fun getting a call late at night from a disgruntled printer and having to perform an emergency fix. Don’t gamble if you can help it.

Now that all your images have been edited and saved as flattened tiffs, it’s time to pick which side of the street you’re going to drive on. If you’re dealing with art that must be printed on a conventional 4 to 6 color press it’s time to change over to the CMYK workflow. And we hope you have properly calibrated your monitor. The shift to CMYK will need to be managed. Save your CMYK art as a new file, don’t overwrite your RGB file. You may need it at some future date. BPI always adds the color space and profile to our file names (for example, FileName_SWOPv2, FileName_Gracol06, FileName_PrinterNameG7, etc…).

Now, you’re probably wondering what an appropriate CMYK profile is. In the United States, US Web Coated SWOP v2 is almost a default. However, a number of printers and large format providers have moved to Coated Gracol 2006. Some print providers have a custom G7 profile and can provide you with one to install in Photoshop. It’s always a good idea to call and ask.

Finally, let’s spend a little time talking about color conversion. Whether your converting from RGB to CMYK or CMYK to RGB you should treat conversion as a one-way street. Please take another look at the workflow diagram. Notice the arrow from RGB to CMYK. RGB is larger in color space then any CMYK profile in existence. BPI usually, about 90% of the time, has to perform color adjustments on a CMYK image to match (as close as possible) the appearance of the RGB counterpart. And, we do our CMYK color adjustments in a non-destructive manner with adjustment layers and masks. Once those edits are complete, we save a flattened tiff copy of the CMYK multi-layer Photoshop file.

You are now ready to construct your art.

How to Have a Bulletproof Workflow

21 Feb

So how do you manage your projects so you get predictable results?  Answer: manage the two different forms of digital assets (raster and vector) so that the color range of your print file fits within the range of your output device.  This is sometimes called a CMYK neutral workflow.

Let’s talk a little bit about print files.  The basic types of print file are the JPEG, TIFF, EPS (encapsulated postscript) and the PDF aka…Acrobat file.  JPEG’s and TIFF’s are strictly for raster/image/photo file types.  EPS and PDF/Acrobat files can contain raster and vector art.  You may have heard of postscript (PS) files, but it’s used less and less these last few years. Postscript has essentially been replaced by encapsulated postscript (EPS).  For the sake of a more compact post, let’s concentrate on the EPS and PDF file types.

There are several structural differences between the two file types.  But, the main difference is ICC profile support. The EPS file does not support the inclusion of ICC profile data; Acrobat does.  And this is why so many printers and large format service providers use EPS as their preferred print file.  What your output provider wants to avoid is a conversion phenomenon akin to double-dipping.  Most RIPs look for profile data.  When they find it, they will (unless managed by the RIP operator) apply another instance of image compression to the print file to fit the color range of the specified ICC.  In other words, your compressed photo gets re-compressed.

ICC’s are not really a perfect model for vector art.  Think back to the diagram, InkjetVsSWOP.png in a previous post. If you strictly interpret the 3D lab image for offset printing, you would conclude that a perfect green (100% cyan and 100% yellow) can’t be achieved on an offset press.  We’ve all read enough magazines to know you can get bright yellows, reds, greens and rich colors from offset printing.  So, what’s going on here?

You’ve probably guessed it.  At some point, your output provider is discarding the ICC profile information.  And it sounds like heresy after all you’ve heard about the necessity of working with agreed upon profiles for color management.  But don’t let your head explode just yet.  Let’s get back to image management.

Image management is simply making sure all your elements (text and photos) conform to the range of your final output device.  Pick the appropriate workflow and work with the end product in mind.

Here are a few tips for you budding graphic designers:

Consider color conversion a one-way street for your vector art.  Your classic light blue (100% cyan) will appear similar when you switch your file to RGB. But, if you were to switch your file back to CMYK the values are transformed to roughly 70% cyan and 14% magenta.  We always make my vector art in CMYK. That way, if we have to make an RGB graphic from it we don’t have to worry about missing a corrupted value for print.  Also, our web graphics will more closely resemble my print files.

Do NOT convert vector art to an ICC profile. Occasionally, you’ll see this option when “Placing” (linking to an external file) or pasting other art into your current working document.  The color values will shift in an unpredictable manner, just think back to what happens to 100% cyan when you change it to RGB and then change it back to CMYK.

Make sure all your scans, photos and Photoshop art share the same profile and color space before assembling your art.  We know most applications have a “Convert to Profile” export option.  This is not a reliable way to work.  When you employ blind processing, you’re asking for an unpleasant surprise. You’re much better off doing the image work yourself.

Use TIFF’s instead of JPEG’s (and ZIP compression when exporting to PDF). Once upon a time, JPEG compression was the recommended way to save images for print due to limits on memory and processing power. One way JPEG compression controls file size is by consolidating color together within a certain range of values.  You may have heard of JPEG’s as a lossy (or lousy, if you’re as picky as we are about image quality) form of compression.  If you’ve ever wondered where those boxy looking squiggles or blocky halos around text came from in digital art, now you know.  In addition, the default compression for saving as a PDF is JPEG.  When you pile JPEG compression on top of JPEG compression you’re just asking for an unattractive result.  We now have more memory, much more powerful CPU’s, graphics cards and RIP software.

If you want more information on JPEG compression, check out the Wikipedia page: http://en.wikipedia.org/wiki/JPEG

And finally, CYA!  Conserve Your Assets!  Always keep customer supplied originals, unaltered.  The client may ask for them at some point.  You may need to compare appearances or justify edits and output with your client standing over your shoulder. CONSERVE YOUR ASSETS; it bears repeating. 🙂

PS: You may have noticed the inclusion of the Light Jet and Durst Lambda under Large Format RGB. Conventional large format inkjet imaging has progressed to the point of photo quality output which can (IMHO) outperform the Durst and Light Jet machines.  Also, new archival, acid-free papers and fade-resistant inks are eliminating the advantages of large-format photo output for lifespan.

Those Pesky Profiles

16 Nov

RGB

Color comes in 2 basic flavors CMYK and RGB. RGB is the native computer display space named for the 3 channels of phosphors which when excited produce color images.  RGB is also known as additive color (see RGB image to the left).  CMYK refers to the basic 4-color separation process commonly used for commercial printing.  It is named for the four colors (cyan, magenta, yellow and black) commonly employed to print full-color images.  CMYK is also categorized as subtractive color (see CMYK image below right).  Other terms that have been thrown around are transmissive (because the color from you monitor is a signal source – with the signal being light) and reflective (because the image you see from a printed page is actually made up of the visible light that is reflected, i.e…not absorbed, by the inks and paper).

Additionally, art comes in 2 basic flavors, vector and raster.  Raster art is the classification for photographic, continuous tone images.  Vector is the term applied to images that are made of solid shapes (called fills) and solid lines (called strokes).  For example, a satellite photo of your house from space is raster and a street map of your neighborhood is vector.  You and I both know that digital art can contain both raster and vector elements but let’s keep things simple for a little while.

So, where do profiles (called *ICC profiles) come into play?  We probably need to provide a little background here.  ICC is short for International Color Consortium, a group founded in 1993 by Adobe, Agfa, Apple, Kodak, Microsoft, Silicon Graphics, Sun Microsystems, and Taligent.  Sun and Microsoft have since left the group and Canon, Fujitsu, Hewlett–Packard, and Lexmark have joined.  The purpose of the ICC was (and is) to develop standards for color display and reproduction across computer operating systems, hardware and software platforms.

CMYK

Think of ICC’s along the lines of a child’s toy from the early 60’s (back when John Wayne road dinosaurs across the earth and we made our images by rubbing 2 sticks together over a fire made from discarded bell-bottom jeans), the printed balloon.  Yes, once upon a time children would actually play with cheap blow-up balloons.  The images Bugs Bunny, Sylvester, Tweety, Planet Earth and the Moon only looked right at a certain size.  If you tried to blow ’em up larger the images would not stretch uniformly.  They would stretch the most where the ink coverage was thinnest and usually wrinkle a bit right at the edge where the ink was heaviest.  If you let the air out, the balloon would almost do the opposite.  The lightly inked areas would shrink the most, the edges next to a heavily inked area would wrinkle and the inked portion with the heaviest coverage would pucker out like a bad tire ready to blow.  ICC profiles are specifications for color range and appearance under certain working conditions.  Or, how much air you should put in a balloon with a certain type of image on it.

ICC profiles have 2 functions, display and print production.  If you would like to get a direct experience of the display function open any Photoshop file (in Photoshop, of course) and select Edit>Assign Profile. Make sure you check the Preview box and select a profile from the Profile drop-down menu.  At present, the numerical values which govern color in your image are unchanged.  But the appearance of the file will be adjusted to approximate how those values would image in a different profile or printed with a particular device (provided you have updated your monitor profile).  However, if you convert your color file to another profile space the numerical values are changed to fit within the new space.  If you are employing the latest edition of Photoshop you may not notice a visual difference when you convert to another profile.  Photoshop CS5 and CS5.5 will honor the original appearance of your file by changing the color values to preserve the original appearance (intent) in a new environment.  This preservation of appearance is called “color fidelity”.

In print production, ICC profiles are necessary to assist the RIP (raster image processor) in interpretation of the numerical color values especially when one device is attempting to mimic the appearance of another (for example: you are printing to a desktop device but you want to emulate the appearance of a US standard sheetfed printing press employing a coated paper).

LAB vs sRGB

Does employing ICC profiles give you a guaranteed result?  Unfortunately, no.  Even if you have profiled your monitor, keep in mind that all monitors are not created equal.  Your image (especially photographic ones) may contain color ranges outside of the ability of your monitor to display (see LAB_Vs_sRGB and RGB Color Space images).  Those out of range colors may affect the amount of shift you experience when you convert an image from its native color space to an output profile like U.S. Web Coated (SWOP) v2 or U.S. Sheetfed Coated v2. Consider they implied challenges when compressing a photo in Pro-Photo into a standard CMYK environment.  If you compressed the same image with Relative Colorimetric intent first and Perceptual intent second, you just might get 2 very different results.

RGB Color Spaces

Also, consider that device profiles like U.S. Web Coated (SWOP) v2 or U.S. Sheetfed Coated v2 are approximations. A good press department and high-quality RIP can exceed expectations and a bad press department can lead to a lot of costly disappointments.

%d bloggers like this: