If you design for print, and specifically for materials that will be printed on traditional offset lithography presses, you either already know about Total Ink, or really should know. In offset lithography, your designs are replicated on paper by little dots of ink of various colors (typically, Cyan / Magenta / Yellow / Black, or “CMYK”, and “spot” colors). These little dots of ink hit the paper in what is known as a halftone pattern. If you bust out your loupe and take a look at anything printed this way, you will see the halftone patter. It looks sort of like this:
You can see how the patterns of dots overlap one another. How much they overlap is called “ink density”, and is something that you can control in Photoshop. The info palette is where this information lies (Window > Info, or F8). If you are in CMYK mode in your Photoshop document (Image > Mode > CMYK Color), it likely looks like this:
The values show in this palette represent the values at the location of your cursor in your Photoshop document. If this isn’t what your info palette is showing, you can easily change what it shows by clicking the little eyedropper icon in both the top panels inside this palette:
Why Should You Care About Total Ink?
Because different presses and different papers can only handle so much ink because of something called dot gain. Dot gain is how much the little halftone dots “grow” when they hit the paper, much like a ring of wetness on a bar napkin when you set your cocktail down. Too much of this going on, dots will start pooling into each other, and you will get nasty dark/muddy areas with loss of detail.
The “rule of thumb” with total ink is 300%. This is why the default mix for rich black in Photoshop is 75/68/67/90 (Add that all up and you get 300).
As they say, rules are meant to be broken. If you are printing on really cheap uncoated stock (like newsprint), your total ink is going to need to be a lot lower, closer to 200. You might be able to go over 300 on a really nice press with really nice paper. Talk to your printer, they should be able to tell you all about this and what your limitations will be.
The important thing to remember is that Total Ink is your responsibility as a designer. A sharp pre-press team might be able to alert you before press time that you are having issues with that, but don’t count on it.
What if my Total Ink is too high?
So you are mousing over your entire image and you come across a heavily-saturated area and your total ink is reading over 300. Being the astute and detail-oriented designer that you are, you want to bring that value down. One way to bring total ink down is to reduce the saturation of the image. This is a “brute force” tactic that can work great if your entire image is riding high, but is generally not a good idea. A more graceful technique is to use curves (Images > Adjustments > Curves) to target high saturation areas and bring values down in a more subtle way. So the area that you found that was reading over 300 you notice is only a little over 300 and is heavy on red. This is a great opportunity for curves:
With the curves dialog open, change the channel to “Magenta”. Then click on the upper right handle on the line and drag it straight down just a little bit. What this is doing is altering the values of magenta in your Photoshop document. If you pulled it down to 95, any areas that previously had 100% magenta now will have 95%. Because of how curves works, this is not just a straight drop of 5% of magenta values across the board. If your line is straight, areas in your document that were at 50% magenta will now only be 47.5% magenta, half the drop of the top end. You can even add a new point to this line and drag the 50% back to the dead center and you will get a curved line for even more subtle changes. Experiment! And make sure to have the preview box checked so you can see how it is visually affecting your images.
What if my Total Ink is too low?
First of all, what is “too low”? If you have an area is fairly detailed and is important to you that it stays detailed, you should make sure that there is enough ink being laid down there that it will happen. Take for instance a light line drawing or an architectural plan. If you notice those lines are thin and a really light color, you should definitely check on their total ink values. If they are, for example, some really light screen of black (3-6%), that might not be enough ink for the plates to hold consistently and get good results. Check with your printer for minimum values.
Using similar techniques to reducing ink density, you can up it. Try adjusting the saturation level of your image first, but if that is doing too much, try curves. Upping values with curves is a slightly more tricky. Make sure that you leave the 0% value at 0% (unless you really know what you are doing). Imagine if you were trying to change those 3-5% blacks up to 9-10% and you ended up making all your 0% blacks 4-5% black. That’s going to ruin your whites and cast a haze over the entire image.
Good luck on working with your total ink!