Rich Black vs. Plain Black

I began working professionally in a film house. We would take artwork created on the computer and create films that would then be used by a commercial printer to make plates for the printing press.  It’s a process that is obsolete these days as everything is now direct-to-plate.  But the experience was invaluable.  It taught be the core principle of print work. Everything on the page is made up of four colors – cyan, magenta, yellow and black (CMYK). And unless you use any kind of special Pantone colors, THAT’S IT!

That core principal is at complete odds with what you see on your screen.  The images on screen use a RGB color model – red, green and blue. And the biggest difference between the two is the amount of colors you can generate from a combination of those inks.  While CMYK inks measure the amount of ink you’ll put down on the page (0-100%), the RGB model measures the amount of light allowed to pass thru to your screen.

On a computer monitor, it’s simple. Black = no light. In RGB terms, that’s 0 red, 0 green and 0 blue.

On a printed page, there are many different ways to represent black. The easiest is “plain black,” or 100% black (0% cyan, 0% magenta, 0% yellow and 100% black). This type of black is the best for words printed on the page – especially on newsprint where the different colors don’t always line up. It makes for a crisp, clear reproduction.

You can, however, also create a “rich black” by printing other inks along with black. There are a number of combinations depending upon your end goal. Most common variations include percentages of all four inks. When an RGB image is converted to CMYK, areas of that image that are solid black will have some kind of combination of CMYK depending upon the settings you have set in photoshop.  Keep in mind that you cannot get the same deep, dark black in a CMYK color model as you can in an RGB one.

The hardest part with these variations of black is that you CANNOT see the differences on the computer screen – they all look the same. But you WILL see the different when it’s printed on paper. Try it.  Take a photograph that fades out to black along the edges.  Take that and put it on top of a 100% black box.  While it looks the same on screen, you’ll see a border around it on paper because in reality, the blacks are not the same.

The solution to this problem is to measure the ink values in CMYK inside Photoshop (using the ink dropper tool or looking at the info palette) then creating a matching color in a page layout program (i.e. InDesign). Be sure you’re moving your cursor around to make sure you are taking the most accurate sample. One other thing to note. If you’re trying to match a color from one program to another, make sure both files are using the same color model. Each program converts a little bit differently. Placing an RGB image into a CMYK document could lead to unexpected results. I especially notice this with PMS colors as photoshop will convert it with one recipe and InDesign will use another. It can get infuriating!

One of the required colors inside InDesign is “registration”. The registration color is made up of 100% Cyan, 100% Magenta, 100% Yellow, and 100% Black. This color is used, just like it says, for registration marks in printing. They are the little hash marks in the corners of the document and the little circles in between that help the printer line up each plate. They also mark the trim edges and any fold or perforation lines. It’s crucial that these show up on each color separation for them to be useful.

The special-purpose color “registration” is another potential source of black mismatches. On screen, by default, it appears as R0, G0, B0, so it seems as if it might be the same as black. It’s not. Registration color prints 100% on all plates. If your layout is CMYK, then registration color is 100C, 100M, 100Y, 100K. If your layout is CMYK + Pantone 285, then registration color is 100C, 100M, 100Y, 100K, 100Pantone 285. Registration color is used for, appropriately enough, registration marks, explained elsewhere. Do not use it in place of black. Having that much ink go down presents many problems from a printing standpoint. There’s no good reason to use anything other than Plain Black or a Rich Black variant.