Converting a file to CMYK (cyan, magenta, yellow, and black) color mode is an important step in prepping files for commercial printing. While many home printers use RGB color, commercial printing presses use CMYK ink. By converting to CMYK before sending your file to print, you ensure that the colors you see on screen will match the printed output as closely as possible.
What is CMYK?
CMYK stands for cyan, magenta, yellow and black. These four inks are used in various combinations to create all the colors in printed materials. When mixed together at full saturation these colors create black:
|Cyan||A bright blue color|
|Magenta||A vivid pinkish-purple color|
|Yellow||A bright golden color|
|Black||The absence of light/color, added for detail|
By controlling the percentage of each ink laid down on paper, printers can recreate all the hues, saturations and values needed to produce full color images. CMYK works by absorbing certain wavelengths of light and reflecting others. The more of a certain ink is laid down on the paper, the more light it absorbs.
How is CMYK different from RGB?
RGB stands for red, green and blue. These are the three primary colors of light. RGB color is used for digital displays like computer monitors, TV screens and mobile devices. Pixels in these displays emit different amounts of colored light to create all the colors we see.
With RGB, colors are produced using additive color mixing. This means the primary colors combine to additively create white. With print production using CMYK inks, colors are produced using subtractive color mixing. The inks absorb certain wavelengths of light and combine to subtractively create black.
When converting from RGB to CMYK you are going from an additive to a subtractive color mode. This conversion means some colors can not be perfectly reproduced, leading to possible color shifts. But converting gives you colors more suited for real-world print results.
Why convert to CMYK for print?
Here are some key reasons it is important to convert to CMYK when preparing files for commercial printing:
- CMYK inks are used – Your printer uses cyan, magenta, yellow and black inks to reproduce images. Using CMYK files ensures accurate print output.
- RGB colors can’t all be printed – Some RGB colors fall outside the CMYK gamut and can’t be precisely printed. Converting avoids undesirable color shifts.
- Blacks print richer – RGB black can look washed out or grayed when printed. CMYK black is formulated to print as a rich, solid black.
- Colors are more balanced – CMYK separates establish ideal balances between each ink color for accurate print reproduction.
- Standardized process – Using CMYK is an industry standard that printers expect when submitting print files.
If you were to submit an RGB file to a printer without converting, you run the risk of colors changing from what you saw on screen. convert to CMYK yourself to have greater control over the final printed colors.
How to convert to CMYK
The best way to convert to CMYK is using image editing software like Photoshop, GIMP or Affinity Photo. Here is a step-by-step process:
- Open your RGB file in the image editing program.
- Go to the color mode drop down menu and select CMYK. In Photoshop this is under Image > Mode > CMYK Color.
- If colors shift significantly, adjust them using Levels or Curves. The Info panel helps compare before and after.
- Adjust individual color channels as needed to achieve desired results.
- Convert any non-CMYK elements like RGB images or spot colors.
- Save out the file in a print-ready format like TIFF or PDF.
Some tips for best results:
- Use a CMYK profile like U.S. Web Coated (SWOP).
- Leave color management enabled to maintain color accuracy.
- Convert vector elements to CMYK first before rasterizing.
- Avoid overprinting black text to prevent misregistration issues.
- Keep total ink coverage under 300% for more saturated results.
For a quick conversion, most programs have an option to simply change the color mode to CMYK. But better control comes from manually adjusting with soft-proofing turned on. The Info panel is also useful for inspecting color values before and after conversion.
Other ways to convert to CMYK
While manually adjusting in image editing software gives the most control, here are some other ways to convert:
- Built-in color conversion
- Printer driver controls
- Color management settings
- Online conversion tools
Some programs like InDesign have built-in color conversion settings that can convert placed images to CMYK with the click of a button. Printer drivers also include color controls for converting files to CMYK for that specific printer.
Make sure any color management settings are configured correctly for your workflow. Soft-proofing simulates output so you can see any conversion differences. And free online tools provide a quick method for converting various file types to CMYK.
While convenient, these automated methods provide less fine-tuned control over color adjustments. The best way is still to manually convert each file in image editing software. But for files with minimal color these quicker options may give acceptable results.
What types of files should be converted to CMYK?
For commercial printing, any files with color elements should usually be converted to CMYK. This includes:
- Raster images – Photos, digital paintings, etc.
- Vector artwork – Logos, illustrations, drawings, etc.
- Text elements
- Graphic elements – Shapes, backgrounds, frames, etc.
- Embedded images in documents
Even black and white images are typically best converted to use rich black instead of straight RGB black. The only exception is files meant to print clear with no color, like die lines or foiling shapes.
Ideally, convert images and artwork to CMYK first before placing them in the final layout file. This avoids multiple conversions causing more color shifts. Then make sure any supporting files like logos or templates are also CMYK.
CMYK and color management
To achieve accurate color conversion, pay close attention to color management settings. Here are some key steps:
- Calibrate your monitor to display accurate colors.
- Use a proper RGB workspace like Adobe RGB for source files.
- Choose a CMYK profile that matches your printer’s setup.
- Soft-proof to preview on-press results.
- Enable color management and convert using profiles.
Having a properly calibrated monitor ensures you see true RGB colors before conversion. Adobe RGB has a wider gamut than something like sRGB to represent colors that can’t be printed.
Using the printer’s target CMYK profile, like a SWOP standard, optimizes the conversion for their specific equipment. Soft-proofing simulates the print output so you can adjust for maximum accuracy.
Converting between color profiles rather than changing modes directly gives you the best maintenance of color values. Set up color management properly and you’ll get reliable CMYK conversions.
Converting RGB files to CMYK is a crucial step in preparing files for commercial print projects. Take the time to manually convert images using image editing software like Photoshop for optimal control over final color reproduction.
Pay close attention to color management settings to maintain accuracy throughout the conversion process. And don’t forget to convert all supporting files like logos and graphic elements too. By ensuring everything is in CMYK, you will achieve the closest match between your original RGB colors and professionally printed output.