What is total ink coverage (TAC) and why printers care

Print shops sometimes reject a file because it has “too much ink”, or ask you to keep the “TAC below 300%”. That number is total ink coverage: the four process inks added together at one spot on the page. Here is what it means, why it matters, and how to bring it down without changing how your design looks.

How the number works

In a CMYK file, every color is four percentages. A light sky blue might be 40% cyan, 10% magenta, 0% yellow and 0% black: a total of 50%. A deep, dark background might be 80% cyan, 71% magenta, 51% yellow and 87% black: a total of 289%. That second one is not invented; it is roughly the near-black background of our night-market poster example after a plain CMYK conversion.

Because each ink can go up to 100%, the theoretical maximum is 400%: all four inks at full strength. Nobody prints that. Paper cannot absorb that much ink fast enough.

The abbreviation TAC usually stands for total area coverage. You will also see total ink limit, maximum ink or just ink limit. They describe the same idea.

Why printers care

• Drying. Ink is wet when it lands on the paper. The more layers, the longer it takes to dry or set.
• Set-off. Sheets are stacked straight after printing. Heavy ink can transfer onto the back of the sheet above.
• Smudging and rub-off, especially when the job is folded, cut or handled soon after printing.
• Paper. Uncoated paper soaks up ink and spreads it, so dark areas get heavier and details fill in. Printers usually allow less ink on uncoated paper than on coated paper.
• Cost and speed. Less ink can mean faster turnaround.

Every print shop sets its own limit based on its paper and press. If yours gave you a number, that is the one that counts.

Where high totals come from

Most of a typical design is far from any limit. The problems are in a few places:

• Large dark or black backgrounds converted from RGB. A screen black or dark navy becomes a mix of all four inks. See Printing large dark backgrounds.
• Dark photos, for example night scenes or dark product shots.
• “Rich black” mixes that someone pushed too far. See Rich black vs plain black.
• Dark browns and deep reds, which need lots of magenta and yellow plus black.

How to lower total ink without changing the look

For dark and neutral colors, there are many ink mixes that look almost the same. Cyan, magenta and yellow together make a grayish component; black ink can replace much of it. Printers call this gray component replacement, or GCR. The result is less total ink and usually a more stable dark color on press.

That is what CMYKflow’s Safer for press does. It replaces part of the cyan, magenta and yellow under dark and neutral areas with black. Bright, clean colors with little gray in them are mostly left alone. You pick a strength:

• Light: a gentle reduction.
• Medium: a good default for most designs.
• Strong: the most black replacement, for very dark designs.

The option Deeper blacks keeps dark areas deep and full after the reduction.

Real numbers from our examples

We made three designs ourselves and converted them with CMYKflow. The table shows the highest total ink anywhere on the page (the number printers limit) for the plain CMYK version and for Safer for press at Medium.

The images, ink plates and average figures are on the Examples page. Notice that the plain conversion stays under 320%: Convert to CMYK caps the colors it converts at 320% total ink.

Reading CMYKflow’s ink figures

For every version, CMYKflow shows the ink before and after as an average over the page: all the ink on the page divided by its area. The average is useful for comparing versions of the same file; a lower average means less ink overall. It is not the same as a printer’s limit, which is about the single darkest spot. When you lower the ink with Safer for press, both numbers go down, as the table above shows.

The separations view shows each ink plate of the first page on its own: stronger color means more ink. After Safer for press, the black plate gets stronger in dark areas and the cyan, magenta and yellow plates get lighter there.

Checklist

1. Ask your printer whether they have an ink limit.
2. Convert your PDF to CMYK; for dark designs, choose Safer for press at Medium.
3. Compare the ink figures and the ink plates.
4. If your design is very dark, try Strong and compare again.
5. Send the file and mention the ink reduction to your printer.