It's not a question of standards, it's a question of physics.

Monitor RGB produces colours using the additive system. Colours are produced by mixing the three main components of white light.

CMYK and Pantone colours are reliant on the subtractive system, coloured inks are affected by absorbing the light that is shone onto them.

Any on-screen representation of CMYK or Pantone is only a virtual approximation and will differ from screen to screen and based on the lighting conditions that you view colours under.

It gets kind of complex, but this is why the graphics industry spends millions each year on calibration systems to reconcile the differences between RGB displays, cameras and scanners; and CMYK printers and imagesetters.

Example - PMS Black is #050403 RGB, and 0, 13, 49, 98 in CYMK. Go figure.

This actually raises two questions. There is no RGB equivalent of any of these as RGB does not really exist in the printed world and visa versa. RGB is light, CMYK and Pantones are inks.

There are actually numerous PMS blacks that are premixed prior to putting on the drum of a commercial printer. Whilst both Pantone and CMYK are subtractive colours - most PMS colours have approximate CMYK 'equivalents' - CMYK reproductions rarely match the original PMS specification. This is because Pantone inks are premixed prior to printing, whereas CMYK does its best to hit the accurate colours within the physical limits of the CMYK gamut. After all it only has 4 inks to play with. The Pantone system has far more.

It gets complicated after this.

bouncybunny,

Guess I should explain my background. Though I now design web sites, my training is in technical theater. In fact, I taught lighting and scenic design at Duquesne University. I understand the physics behind the color problems: light vs print, and addative and subtractive mixing. It's just that old thing: They can put a man on the moon, but they can't.... Since I also design for print media, it is more an issue of my clients going "that looks great" when they see it on the monitor, and then being dissatisfied when they see it in print. They don't, necessarily, understand the difference in media. I quess you could say it's wishful thinking on my part that the powers that be work out the problem :)

Ah OK, I didn't mean to teach you how to suck eggs. ;)

The problem is that these days so many proofs are sent as PDFs that clients don't even get to see a printed proof. I just don't see how the color system can be reconciled really.

Yeah, I know. While I send proof via PDF, I also send a hard copy. I TRY to explain to my clients that there will be some color variations, but as I said, they generally do not understand. That is why when I found a comparative chart, I try to use Pantone or CYMK whenever I can and get as close to RGB as technology allows. And then, of course, there are variations in printers too which only complicate matters. And then DPI which many people don't understand either. Again, I get a lot of "that looks great" until they see it printed. My color laser goes up to 1200 DPI, but generally I do not need to exceed 300 to make most people happy I cold go on, but it strikes me you that you fully understand what I am talking about. I guess, in the end, as long as the client is happy nothing else matters.

I quess you could say it's wishful thinking on my part that the powers that be work out the problem

Absolutely! :-)

There's yet a few more elements involved in getting RGB to play along with CMYK.

The pigments for inks are ground from natural earth substances, and are as controlled as possible but unfortunately do NOT fully represent the color. (Japanese printers actually have a slightly higher standard in CMYK inks than the U.S., but the difference is minor.) This is called color contamination - the color Magenta still reflects a great deal of blue light, the color Cyan still reflects some red. Yellow is the closest to yellow, I think it is like 99% yellow light that reflects from it with barely a bit of red light.

Color contamination also exists throughout the capture and digitize process, even when we used lasers to scan slides and reflectives, the quality of color value captured was affected by the copy itself as well as the light passing through the air.

Color contamination alone is responsible for most of the fine-tuning problems in traditonal printing, the most facinating and comprehensive book on the topic is Electronic Color Scanning by R.K. Molla. It sits right next to my color theory books, it is a color bible. :-)

Add paper. Paper is never really white. Even if it is as white as you can get, it doesn't reflect pure white in all situations.

Add printing press variables. When you deal with wet pigments, there is ALWAYS going to be a little Cyan color coming off the paper and mixing with the Magenta blanket, and so on for all four colors. Even with the best presses.

Then you have to go and throw in something like this (chiding you now :-P :)

PMS Black is #050403 RGB, and 0, 13, 49, 98 in CYMK.

Let's skip the fact that you chose black - the reasons for the adjustment in RGB were to "emulate" that ink on a monitor and in CMYK (both impossible in reality), taking in all of the above variables. Let's try something like a PMS red, just pick any one of them.

All of the above reasons, color contamination in particular, are why the Pantone systems came into being. You can't get some colors with CMYK. So what did they do? They use different pigments to make their colors. Next time you're at the art store compare a Thalo Red with a Carmine Red or Rose Madder. They are literally ground from different pigments. This is how PMS colors are composed - when looking at a PMS book, look at the BASE color used to create it. You will see many of them are literally different pigments.

If you use CMYK, use a CMYK color picker. If you plan on printing multiple colors, like two spot colors and black, use a PMS color picker. :-)

rocknbil,

I assume you have a lot of color printing experience. Granted, my “training” in color dealt with light and paint and “if it looks Okay from 30’” rule (the accepted minimum distance for an audience member to a set on stage). My “printing” color knowledge is limited. As I said, I use a CYMK laser for my customers on a 100-110 “bright white” paper. I generally give them a 600dpi proof which they then send to a printing company. I have not got any “real” complaints yet, mostly as I said before about the differences between on screen and in print. But as I said, in the end, as long as the customer is happy…. Maye in the future, I'll tap youur knowledge ;)