Should I Use CMYK or RGB for My Design Files?

One of the most common questions in commercial printing is: “Should I supply my artwork in CMYK or RGB?”

The short answer is CMYK.

Understanding a few basic print standards can save time, avoid production delays, and help ensure your printed job matches your expectations.

CMYK vs RGB

Can I send my file in RGB because it looks great on my monitor?

Unfortunately, no. RGB (Red, Green, Blue) is a colour space designed for digital displays such as computer monitors, tablets, and phones. It produces colour using light and has a much wider colour gamut than CMYK.

CMYK (Cyan, Magenta, Yellow, and Key/Black) is the colour space used by commercial printing presses. Because it relies on ink rather than light, it cannot reproduce every colour that RGB can display.

When an RGB file is sent for print, it must be converted to CMYK. During this conversion, colours that fall outside the CMYK colour gamut are replaced with the closest printable equivalent. This often results in noticeable colour shifts, particularly with bright blues, greens, oranges, and fluorescent-looking colours (see image).

Many commercial printers will flag RGB images during prepress rather than automatically converting them. This is because automatic conversions can lead to customer complaints when printed colours do not match what was seen on screen.

If the prepress department converts the file to CMYK, the process itself is straightforward, but the printed result may still differ from your original design. If the artwork contains colour-critical elements such as logos, brand colours, or product images, a new proof may be required for approval, which can add both time and cost to the job.

Best Practice

For the most predictable printing results:

  • Create or convert your artwork to CMYK before supplying it for print.
  • Use the correct ICC colour profile recommended by your printer.
  • Always check colour-critical artwork with a printed proof where possible.

Preparing your files correctly from the start helps ensure smoother production, fewer surprises, and colours that print as accurately as possible.

Image Resolution (DPI)

Image resolution (PPI/DPI) ≈ 2 × the screen’s LPI (lines per inch).

LPI (Lines Per Inch) refers to the halftone screen frequency used in printing.

PPI (Pixels Per Inch) is the correct term for the resolution of a digital image.

DPI (Dots Per Inch) refers to the printer’s output capability, although people often use “DPI” when they actually mean image resolution.

Examples

150 LPI print screen → 300 PPI image

175 LPI print screen → 350 PPI image

200 LPI print screen → 400 PPI image – We save all our images at this setting by default

NEVER USE JPEG FOR PRINT – THERE ARE BETTER FILE SOLUTIONS THAT DO NOT DEGRADE YOUR IMAGE

The “2× LPI” rule (also called the quality factor of 2) is based on the Nyquist sampling principle and is widely used in commercial printing.

There are exceptions:

Some workflows use 1.5× LPI to reduce file size with minimal visible quality loss.

Very high-quality art books or stochastic/FM screening may use different recommendations.