Category: Graphics Trades

How Come It’s Not CMYB, Huh?

Like any industry, printing and graphics have developed its own special language meant to keep outsiders away. In this article, I will reveal the secret terminology that, if you study hard, will allow you to pass as someone who knows something about the trade. Heck, it worked for me. Here we go:

CMYK – Perhaps the most ubiquitous term in printing and graphic, CMYK stands for Cyan, Magenta, Yellow and Black. Wait, whut? you might rightfully quizzle? Why “K” and not “B” for Black? There are competing theories for the development of this term and both hold a logic that makes good sense. Some say the “K” stands for “key colour”, since on a printing press, each ink is in its own printing unit with all other inks registering or “keying” (get it?) to Black. The other idea is that the letter K is used to avoid confusion with B for Blue, Brown or some other ink that starts with “B”. “K” is the exclusive designation in printing technology for black ink that’s used in four-colour process printing.

LPI, DPI, Pixels, Dots – Oh, my, what big picas you have. I’ve heard non-printers refer to the dots seen in offset printing as pixels. This sort-of makes sense in the way that the dots on a computer display are similar to printed dots in that they represent tone or colour to the human viewing the art. Except that printed dots are much smaller, are not in RGB (video display dots always are), are not in fixed positions in a grid (like on a video monitor) and don’t change the perceived colour by varying intensity of three dots (which is how RGB monitors work). Since there’s no such thing as an RGB printing press, the dots on an offset printed piece vary in size to show more or less of a particular colour, usually arranged in a pattern called a rosette for four-colour printing.

RGB – Red, Green, Blue. These are the colours of the video rainbow. There is no such thing as an RGB press. RGB is a colour mode that is used for digital images that display on a colour monitor or video display device. RGB has a much larger gamut than CMYK, so colours can appear richer and more saturated when viewed in this mode.

Gamut – This is the range of colours that can be reproduced in a given colour systems. CMYK can reproduce about 65% of the Pantone 1000. Add OGV (Orange-Green-Violet) inks and that number goes up to about 90%. So, gamut is the range of reproduction of a given colour system.

Contone – Short for continuous tone, this is a reproduction or display method that has no dots, like in offset printing, where all steps from 100% colour to no colour are fully reproduced without interruption. Most contract proofs today are contone proofs.

Contract Proof – This is a colour-accurate, controlled output proof that a print buyer can view under controlled lighting conditions that can be used as a “target” for printing. The proof represents the ability of the target printing system to reproduce the proofed work.

Don’t worry – there’s lots and lots of wonderful jargon to learn! Catch ’em all and someone may mistake you for a pro. Which you are. Of course.

sRGB versus Adobe RGB

If you’re a pro photographer or photo enthusiast, it’s likely that you’ve come across a debate about sRGB (standard Red Green Blue) versus Adobe RGB. If not, these names represent different colour spaces for RGB images. Digital cameras generally shoot and save in RGB, versus the CMYK (Cyan, Magenta, Yellow and Black) colour space that would be used for typical offset printing. There’s also an extended gamut colour space for offset printing known as CMYKOGV, which adds Orange, Green and Violet to the CMYK space to reach outside of the gamut that can be reached with CMYK alone. There’s no such thing as an RGB offset press. The focus of this article is whether Adobe RGB is preferable over sRGB.

Adobe RGB is a profile developed by Adobe in the very late 1990’s, based on the SMPTE 240m standard. The idea was to include the colour range that then predominately CMYK inkjet printers could reproduce. That colour range could then be displayed accurately on a RGB monitor.

sRGB was developed by HP and Microsoft to profile for various output conditions and released in 1996. sRGB is the default RGB profile for images without an assigned profile.

Despite some significant mis-steps in the creation of the Adobe RGB profile, Adobe included it with Photoshop 5.0. At the time, few to no useful profiles were available, so for Photoshop users, Adobe RGB was, essentially, better than nothing. Because of the development errors, Adobe RGB was not as accurate as sRGB.

Because sRGB became an IEC standard in 1999, all images viewed on the web are sRGB by default. sRGB has a slightly smaller gamut, or the range of colours that it can reproduce) than Adobe RGB. In practice, this difference is too small to make for a deciding factor.

The advantage of the slightly expanded gamut of Adobe RGB is apparent in output on certain types of images BUT the workflow has to take into account that display images on the web will be sRGB. So, it would be necessary to maintain at least two image files for each image, one for the source image in Adobe RGB and a second for web display in sRGB. Using straight Adobe RGB images in a web environment, that is, a web browser, will yield dull and inaccurate colours. Proper conversion of each image is essential.

For the photographer whose images are destined for print, it should be understood that outside output houses may not expect or account for Adobe RGB images in their RIP (Raster Image Processor) workflows. So, the output, assuming the image is being reproduced by inkjet or dye sublimation, will be inaccurate. Also, some output house don’t accept sRGB images at all, which would mean that the photographer dedicated to Adobe RGB would have to add another image to his or her growing library of digital assets – one specifically for output at a given output house. Since time is money, Adobe RGB may be the costlier choice for little, if any, gain.

Modern inkjet and dye sub output devices can reproduce a significant portion of either the sRGB or Adobe RGB spaces, but not the entire space of either as compared to a high-end video monitor. For most purposes, from commerical to fine art output, sRGB is more than sufficient for pleasing and ‘correct’ output and is more likely to be viewable for most of the gamut on a modern monitor or HDMI display, versus Adobe RGB’s 75% reproduction on an sRGB monitor.

So, both colour spaces can yield accurate reproduction but one, sRGB, is practical across more media without jumping through hoops.

CMYK versus RGB

Not every colour that can be expressed in L*a*b* can be reproduced in either the RGB ranges or “gamut” or as CMYK. This illustration can help to illustrate where the reproducible colour ranges fall:

The L*a*b* colour space provides coordinates for ALL visible colours, not all of which can be reproduced in other colour spaces. In the illustration shown here, even RGB can’t plot every colour in the visible spectrum and CMYK is the smallest subset of all of the color spaces. Custom-mixed inks, depending on the pigments, are much more flexible but it may not be possible to reproduce on an actual device.

Extended gamut printing goes much farther than ordinary CMYK by using technology to add standards-defined Orange, Green and Violet inks to print with seven colours. So, a deep Reflex Blue that would be impossible for CMYK alone has Violet added to extend the offset or digital printing process. This makes possible the printing of spot colours without having to custom-mix a Pantone colour. It’s also possible to formulate out of CMYK+OGV custom “brand” colours to match specific targets. While this process isn’t suitable for every customer’s needs, it can be a very cost-effective alternative to multiple spot colours. CMYK+OGV techniques can reproduce from 91% to 95% of the Pantone Matching System, within a variance of as little as .08 delta E to as much as 5 delta E, which is the difference between the target colour and the reproduced colour.

For cosmetics clients that are looking to represent skin tones across media, we probably have a reasonable chance of locating the colours in question within a CMYK space and representing those colours fairly in RGB. Since web and print viewing conditions and technology are completely different, direct “matches” between CMYK and RGB are not likely, though it will probably be close enough for practical use as long as it’s disclaimed as such.

Overprint Preview, Layers and Separations in Acrobat Reader, Pro and DC

To view overprints in Acrobat Reader, Pro or DC, open the source document, navigate to the “Preferences” option in the Acrobat menu. In the window that opens, highlight “Page Display” under “Category” in the left-hand pane. In the right-hand part of the window, locate the option “Use Overprint Preview” and select the option to the right from the drop-down choices, “Always”. Here’s a view of that setting:

Acrobat Pro and DC can “toggle” overprint preview, as well as view separations. For professionals in the printing industry that are viewing artwork for mechanical correctness, this is the correct and recommended way to view that artwork since this is how it will be separated to plates and go to press.

Separations are often mistakenly called “layers.” Layers are just that – different levels in a files that may contain different elements, like images, decoration or other features, placed on these different levels for mechanical reasons. Any number of different colours can exist on a single layer, but only one ink (or varnish or emboss or stamp, and so forth) can exist per separation.

To view separations and overprints in Acrobat Pro or DC, navigate to “Tools” and select and click “Print Production”.

In the pane that opens on the right-hand side of the viewport, select “Output Preview”.

In the Output Preview box that opens, note the option near the top of the window called “Simulate Overprinting”. By alternatively ticking and un-ticking this box, the displayed document will alternate between appearing with and without overprint.

Directly to the right of the “Simulate Overprint” option, Acrobat displays whether or nt overprint is present in the document being previewed. Separations can be toggled on and off by selecting the tick mark next to the colour name in the “Separations” pane on the lower half of the Output Preview window.

If there are layers in the file being viewed, those can be viewed by clicking the right-facing arrow on the left-most edge of the displayport. 

Several icons will become visible above the arrow’s location. Click on the icon that looks like layers of sheets of paper.

Whatever layers that are present will appear in the Layers tab that opens. Clicking on the eye icon will turn individual layers on or off.This feature is not meant to check colour separations.

Checking seps should be done ONLY with all layers on, just as the file would be used for production. Otherwise, there is a reasonable chance that an element on a turned-off layer that will interact with the rest of the art in the document when the going to press will not be noticed.

No Fonts Allowed

When a different font is substituted for a missing font in a client’s file, the replacing font may have different spacing, or kerning, between the characters. This difference will cause differences in how lines break in paragraphs, so a word that appears at the end of a line on the client’s computer may bounce down to the following line, or the word at the beginning of the following line may bounce up to the prior line. Even if the font has the same name, different vintages and versions of fonts can be, and often are, different. Special characters that may have been added to the client’s set of characters, like a Euro symbol or the special E for the euro weight claim won’t be in a standard set of characters necessarily and will be replaced by a ‘wrong’ symbol, like a check mark or a box.

To avoid creating a problem, it’s been a best practice in desktop publishing for the last several decades to deliver files with fonts turned into outlines so that the style and position of the type is locked to how it appeared in the client’s layout environment.

This is very easy to do in Illustrator.

•    Open the file in Illustrator.
•    From the menu bar, select ‘Select>Object>All Text Objects’
•    From the menu bar, select ‘Type>Create Outlines’
•    Save As Copy with the same file name, adding “-OL” to the end of the file name to indicate it’s the outlined file.

That’s it. The vendor receiving the file can’t accidentally alter the type because there is no type in the document and fonts issues are gone because there are no fonts in the file. The original layout is untouched should upticks or revisions be needed in the future.