How to Prepare Black and White Images for Adobe® InDesign® and PDF to Book

NOTE: This document details black and white image prep for Adobe® InDesign® or Blurb's PDF to Book workflow. For information about image prep for Blurb BookSmart®, see How to Prepare Black and White Images for Blurb BookSmart.

The biggest challenge printing black and white images in a four-color process is the potential for the introduction of a color cast. A color cast – regardless of the type of four-color process – is emphasized when a color space is converted down from the much larger RGB color spaces (sRGB, AdobeRGB, ProPhoto, etc.) to CMYK. There is an accepted amount of color drift within the world of digital offset presses and this acceptable delta is defined by Hewlett-Packard. Most people would never notice a slight shift in Cyan within a full-color image, but a color shift in black and white images is another story.

So what to do? The best thing you can do is to be sure there is no underlying color cast in your images prior to importing into Adobe® InDesign® or your preferred book layout tool. (For BookSmart look here). Here’s how:

1. Remove all color from your image

   
   Figure 1. Black and White Adjustment

   There are several ways to convert color images to black and white using an imaging tool such as Adobe® Photoshop®. We recommend using the Black and White function that you’ll find in newer versions of Photoshop. The desaturate option can be used although it is not recommended due to its lack of control. Do not simply change the image mode to Greyscale. Because the book prints using four colors (CMYK) the greyscale mode will neither be honored nor produce the best results. The Black and White function is available only for RGB color space images. You will need to work on a RGB version of your image before converting it to CMYK.

   
   Figure 2. Black and White Adjustment

   Using the Black and White Adjustment

   • Edit > Adjustments > Black and White. This method allows you to tweak the contrast of the image.
   • By adjusting the sliders you will get a real-time preview of your effects and can control how you would prefer colors to translate to a black and white image.

   Increasing Contrast

   A common issue with color to black and white conversion is a loss of contrast. You can add contrast to your image by applying a slight s-curve to your images.

   • Image > Adjust > Curves. You can also do this as an adjustment layer.
   
   Figure 3. Increasing Contrast

   By using an s-shaped curve, you can improve contrast by darkening the shadows and lightening the highlights.

   You can use this same technique to lighten up dark areas overall or to improve the midtone range of you images if they are too dark. Just grab the curve either in the middle or slightly to the left of middle and pull up.

   You can also use the eyedroppers (circled in screenshot) to select your highlight and shadow areas of your image for better contrast control.

   Using the Desaturate Adjustment Instead

   
   Figure 4. Desaturate
   • Edit > Adjustments > Desaturate. Although this is the quickest method, it doesn’t allow for any adjustments and may result in both a loss of contrast and a muddy looking image.

   Your file is digitally neutral. However, you may notice that the image is flat or muddy. This is due to the nature of the desaturate command. Colors that share the same lightness value but have vastly different hues will convert to the same grayscale value. This means that you will often lose contrast between colors leading to a flat image. Newer versions of Photoshop have a Black and White adjustment that we recommend for more control and better results.

2. Optional: Add a Color Tone (or Sepia) to Your Image

   Removing all color from your image guarantees that there is no color cast present in your images. However, some photographers prefer to have a slight warm (reddish) or cold (bluish) color cast to match a traditional feel of black and white paper or sepia tone process. There is a benefit in adding a tone, as it can be easier to hold a color tone than a true neutral black and white print. There are several strategies to add a color tone to your image. We explore two of them below.

   Use a Photo Filter

   • Image > Adjustments > Photo Filter. Select from the presets or choose you own color.

   Adjust the Curves

   If your version of Photoshop does not have the Photo Filter feature, you can accomplish similar effects with the Curve tool.

   • In the Curve window, select either Red, Green, or Blue from the drop-down menu depending on the hue you want. Then grab the middle of the curve and pull up or down to see the sepia effect. Only a slight move is needed to give your image some color!

3. Convert the file to CMYK

   Our Adobe InDesign plug-in and PDF to Book workflow work best with CMYK images. CMYK images have a much higher level of control over blacks. If your images are in CMYK, you are ready to go. If you use Adobe RGB, ProPhoto RGB, sRGB, or another RGB color space, you can use Adobe Photoshop to convert your images to CMYK before placing within InDesign or your preferred layout software. Photoshop is a fully color managed application and can convert your images with a minimal amount of color shift. Make sure to always work on a copy of your image and preserve the original in its original color space.

   First, if you have not done so already, download and install the Blurb ICC Profile. The ICC profile and step-by-step directions can be found in our Color Management Resource Center

   To convert the file to CMYK

   
   Figure 5. Convert to Profile
   • Select Edit > Convert to Profile (you may also need to select “Show All Menu Items” if the ”Convert to Profile” item is not available.)
   • Select Blurb_ICC Profile.icc as the destination.
   • Select Perceptual as the Intent and Adobe ACE as the Engine to achieve the best possible match between RGB and CMYK without losing subtle gradations and transitions. Select Black Point Compensation to preserve shadow detail. Select dither if you want to add a small amount of digital noise to break up gradients that are banding. You should always use dither if your image contains large areas of subtle gradations.
   • Click OK to complete the conversion.

4. Save image files

   
   Figure 6. Saving a Copy

   Once you have made all you edits you are ready to save your files and import them into InDesign or your preferred book layout tool (other than BookSmart, which requires sRGB files).

   Saving Files in Photoshop

   We recommend that you save a copy of your Photoshop files that have been converted to CMYK and keep your originals as they are. The CMYK files should be saved as JPG or TIFF with Embed Profile checked.