Why You Should Import RGB Images Into InDesign and Convert to CMYK On Export
[This article was co-authored by Claudia McCue and David Blatner.]
Yes, we know you probably learned to convert images to CMYK in Photoshop before placing them in InDesign. And yes, we know that you’ve been doing this since 1989 with PageMaker 2. But you know what? This is the 21st century now and it’s time to wake up, smell the coffee, and change your ways for the better.
So, even though we’ve been saying this for 15 years, maybe you haven’t heard it… so we’re going to say it one more time, with emotion:
You can leave your images in RGB. You don’t need to convert them to CMYK. And in fact, you probably should not convert them to CMYK (at least not in Photoshop).
As we have traveled around the world giving presentations about InDesign, Photoshop, and publishing, we’ve been constantly amazed at the number of people who are still using the old, 20th-century “convert to CMYK” workflow. And we feel a bit like someone walking into a jail announcing, "Hey, the doors aren't locked! You don't have to stay in here!" Some people immediately jump up and taste freedom; some wake up to the new realization slowly; and others refuse to believe it, knowing that staying behind bars is more comfortable than facing the unknown.
True, in Ye Olden Days, the RIPs (Raster Image Processors) used by commercial printers to translate PostScript from graphics programs did a lousy job of converting RGB to CMYK, resulting in muddy, inaccurate color rendering. Thus it was that, in all the land, a decree went out, ordering that Thou Shalt Convert Thy RGB Images To CMYK Before Sending Thy Job To The Printer.
Fast forward to Modern times: Current print workflows perform excellent conversions of RGB to CMYK, and some printing processes — such as digital presses and large-format inkjet output — actually provide better and more vibrant output when fed with RGB content.
You’ll still encounter print providers who insist on the submission of CMYK content, partly because “that’s how we’ve always done it” (and partly because some very small shops might still be using antiquated equipment).
Of course, you should always consult the printer to determine how your job should be submitted — never assume!
But here's the truth: InDesign can convert your images to CMYK as well as Photoshop can. It uses the same color engine, so you can get exactly the same results. (There are a few, relatively rare exceptions to this rule, which we’ll cover below.)
So now, in the 21st century, here's the new rule: Keep your images in RGB as long as you can, place them, as RGB, into InDesign… and then, only if you have to, convert to CMYK inside InDesign when you make your PDF files.
We're Talking Pixels Here
We want to be clear that we’re talking about pixel-based images here -- bitmapped images, such as those from Photoshop. We’re not talking about vector artwork. InDesign can convert RGB vector artwork, too, but it won't necessarily end up the way you'd expect. If you're using Illustrator or a similar vector-drawing tool to make logos or illustrations that will likely be printed, we generally recommend using CMYK or spot colors, not RGB.
Similarly, when you're applying solid colors to objects in InDesign—and those documents are headed for print—you should use CMYK or spot color swatches, not RGB, in the interest of predictable conversion. For example, if you apply a solid RGB color 0/255/255 (which is bright cyan) to a frame and then print it, you’re not going to see a perfect 100% cyan in print. Instead, you’ll get something like 52% cyan and 13% yellow. That’s just par for the course when it comes to converting solid RGB colors to CMYK. So if you want 100% cyan, you should spec it in InDesign as 100% cyan.
Tip: In the Swatch Options dialog box, InDesign and Illustrator both warn you if an RGB color falls outside what CMYK printing inks can reproduce (called the CMYK “gamut”). Click the yellow alert triangle to convert to the closest in-gamut RGB value, so you won’t be shocked when the color is converted to CMYK.
Note that we’re emphasizing “for print.” If you’re creating documents that are primarily for on-screen viewing, then solid RGB colors are great, even in vector artwork!
Why Placing RGB Images is (better than) OK
What’s so wonderful about Red-Green-Blue? RGB is the native language of digital cameras and scanners, and it can faithfully portray a wide range (gamut) of colors, from vibrant oranges to brilliant greens, from bright white to dramatic black. Cyan, magenta, yellow, and black (CMYK) printing inks can render a smaller range of colors, resulting in disappointing approximations of those oranges and greens, as well as other commonly desired colors, such as navy blue.
When you convert RGB images to CMYK, you lose those out-of-gamut colors, and they won’t come return if you convert back to RGB.
But here’s the important part: Just because you place RGB images into InDesign doesn’t mean you’re sending RGB images to your printer! InDesign can convert those RGB images to CMYK when you export your PDF file. (It changes them in the PDF file without modifying your originals on disk.) So by placing RGB images, you have a choice: send RGB or CMYK—and if you choose CMYK, then you have to decide which CMYK.
The “which CMYK” is a new question for a lot of people, because they think there’s just one CMYK. But there are thousands of different CMYKs! So when you convert an RGB image to CMYK in Photoshop you’re targeting (optimizing for) just one of those. And, unless you use the correct target printing profile to perform the conversion, you may have stripped out RGB colors that could have printed successfully. For example, if you used a profile for uncoated paper when preparing images that will print on coated stock, your conversion is way off. Plus, printers who have implemented a full color-managed workflow want your images as RGB because they can convert to CMYK at the last stage before printing, optimizing output for the final printing platform.
Even better, sticking with RGB means you can use the same images for different jobs: the same document could be printed on Web press coated paper one day and then sheetfed uncoated paper the next. Or you can use the same image assets in multiple ways— for example, a brochure printed on a sheetfed offset press, and a companion banner printed on a grand format inkjet device. The results might be very slightly different, but you will be able to get the best quality from each, rather than target just one printing condition and then leave the other one to chance.
Keep in mind that most modern printers can handle RGB content. Converting to CMYK early won’t necessarily ruin the outcome, but might result in the loss of some color gamut, especially if the job is going on a digital press such as the HP Indigo or a wide-gamut device such as a large format inkjet printer.
So talk with your printer: If they say they can accept a PDF/X3 or PDF/X4 file, that means they can handle the conversion from RGB to CMYK themselves (and, again, they’ll probably do a better job of it than you can). If they say they need all your images converted to CMYK, then use InDesign to do the conversion when you make your PDF.
(Some of you are saying, “But I don’t make a PDF, I send my native InDesign files to the printer.” Well, um, that’s nice. We find sending PDF files to be far more reliable, assuming the file is created correctly. If you aren’t sure how to make a great PDF file, see the links to our video courses and books at the end of this article.)
Of course, your printer may request that you send an InDesign package with the PDF so that any necessary changes can be made more easily. Printers often have to modify otherwise perfect files to accommodate the final printing process. But if the file and the PDF is made correctly, they shouldn’t need to touch your original files.
How to Convert to CMYK When Exporting a PDF
When your printer tells you they do prefer CMYK images, here’s how to export your PDF files from InDesign:
- Choose File > Export.
- Choose PDF (Print) from the Format pop-up menu.
- Choose a PDF Preset (such as PDF/X-1a if you want to flatten all your transparency, or PDF/X-4 if you want to maintain your transparency).
- Set up all the other options in the Export PDF dialog box (compression, marks and bleeds, etc.)
- Finally (here’s the important part), in the Output pane of the Export PDF dialog box, choose Convert to Destination (Preserve Numbers) from the Color Conversion pop-up menu. Do not choose “Convert to Destination” (without the “preserve numbers”) part, unless you really seriously know what you’re doing. Preserve Numbers means “if I have a CMYK image or CMYK colors in my file, then leave those alone.” You want that.
- Then, in the Destination pop-up menu, choose which CMYK you are targeting. Again, in the best case scenario, your printer will give you a color “profile” you should choose. But if they insist on CMYK, and for some reason can’t provide a custom profile, ask if they’re running the job on a web press or on a sheetfed press; then you can at least use canned profiles. For example, for uncoated stock on a sheetfed press, you might want to use Uncoated FOGRA29.
- Click Export.
The PDF you get will be all CMYK and your printer will be happy.
When It Makes Sense To Convert to CMYK Before Placing an Image
There are a few times when we convert images to CMYK in Photoshop before saving and placing into InDesign:
- First, if an image includes a color that must show up with a specific CMYK value. For example, let’s say you have an image of a banner with a giant corporate logo on it, and that logo has to be a particular CMYK value. Or if you have an image that contains an area of solid magenta that really is supposed to be solid, 100% magenta.
- Second, there are some image retouching situations where you really need to adjust just one plate. The classic example is when you have an image of a model’s face and you want to adjust just the black plate.
In those cases, we would convert to CMYK in Photoshop and then adjust the color on individual channels/plates to match the required color. But those are the exceptions, not the rule.
And, for goodness sake, if you are going to use Photoshop to convert from RGB to CMYK, choose Edit > Convert to Profile (instead of just choosing Image > Mode > CMYK). If you just change the image mode, Photoshop uses the values dictated by your current color setup (Edit > Color Settings). That’s fine if your current color settings match your ultimate printing process. But choosing Edit > Convert to Profile helps ensure that you’re choosing the correct target (“which CMYK”) each time.
For More Information
Want to learn more about preparing images for print, exporting documents to PDF, and managing your color? Check out:
- InDesign Insider Training: Print PDFs
- Print Production Fundamentals
- Real World Print Production
- Real World InDesign
- Real World Color Management (an oldie, but a goodie)