Is color management for me?

The material in these guides is recommended for advanced users – such as creative professionals – who require the highest possible precision in rendering color. For most users, an understanding of the advanced concepts of color management is not necessary to produce a great-looking book with Blurb.

For more information, visit our Color Management Resource Center.

How to Prepare Black and White Images for Blurb BookWright

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

The biggest challenge printing black and white images in a four-colour process is the potential for the introduction of a colour cast. There is an accepted amount of colour 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-colour image, but a colour 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 colour cast in your images prior to importing to Blurb BookWright. Here’s how:

  1. Convert your images to the sRGB colour space using Adobe® Photoshop®

    All images must be sRGB for BookWright submission. If your images are already in sRGB, you are ready to go.

    BookWright does not accept CMYK images but it accepts RGB or greyscale images with sRGB being the preferred colour space. When importing into BookWright all other RGB images are converted to sRGB. However, this automatic conversion from RGB to sRGB may not be optimal for your specific images and may introduce an undesired colour cast to black and white images.

    Figure 1. Check Document Profile
    Figure 1. Check Document Profile

    If you use Adobe RGB, ProPhoto RGB, or some other RGB colour space, you can use Adobe Photoshop to convert your images to sRGB before importing them into BookWright. Photoshop is a fully colour-managed application and can convert your images with a minimal amount of colour shift. Make sure to always work on a copy of your image and preserve your original in its original colour space.

    Check that your image is not already sRGB

    • You can do this in Photoshop by clicking on the menu on the bottom left of your image window and selecting Document Profiles as in Figure 1 on the right.
    • Remember, if the image is sRGB, you do NOT need to do a conversion.

    To convert the file if it is not sRGB

    Figure 2. Convert to Profile
    Figure 2. 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 sRGB as the destination.
    • Select Perceptual as the Intent and Adobe ACE as the Engine to achieve the best possible match between Adobe RGB and sRGB 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.
  2. Remove all colour from your image

    Figure 3. Black and White Adjustment
    Figure 3. Black and White Adjustment

    There are several strategies to convert colour images to black and white using an imaging tool such as Adobe Photoshop. We recommend using the Black and White function – available in newer versions of Photoshop. The de-saturate option can be used although it’s not recommended due to its lack of control. Do not simply change the image mode to Greyscale. Since the book is still printed using four colours (CMYK) the greyscale mode will neither be honoured nor produce the best results.

    Using the Black and White Adjustment

    Figure 4. Black and White Adjustment
    Figure 4. 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 colours to translate to a black and white image.

    Increasing Contrast

    A common issue with colour 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 5. Increasing Contrast
    Figure 5. 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 mid-tone range of your 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 eye-droppers (circled in screenshot) to select your highlight and shadow areas of your image for better contrast control.

    Using the De-saturate Adjustment Instead

    Figure 6. De-saturate
    Figure 6. De-saturate
    • Edit > Adjustments > De-saturate. 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.

    In the Info palette, individual RGB numbers should now all be equal (in the example shown in Figure 6 they all read 68), which means that your file is digitally neutral. However, you may notice that the image is flat or muddy. This is due to the nature of the de-saturate command. Colours that share the same lightness value but have vastly different hues will convert to the same greyscale value. This means that you will often lose contrast between colours leading to a flat image. Newer versions of Photoshop have a Black and White adjustment that we recommend using for more control and better results.

  3. Optional: Add a Colour Tone (or Sepia) to Your Image

    Removing all colour from your image guarantees that there is no colour cast present in your images. However, some photographers prefer to have a slight warm (reddish) or cold (bluish) colour 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 colour tone than a true neutral black and white print. There are several strategies to add a colour tone to your image. We explore two of them below.

    Use a Photo Filter

    • Image > Adjustments > Photo Filter. Select from the pre-sets or choose you own colour.

    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 colour!
  4. Saving Image Files for BookWright

    Once you have made all your edits, you are ready to save your files and import them into BookWright.

    Soft-proofing your images for BookWright

    You can soft-proof your sRGB files using our Blurb ICC Profile to get an idea of how the images will look when printed. See our documentation regarding Soft-Proofing for BookWright with Photoshop. The Blurb ICC Profile is available in the Colour Management Resource Centre.

    Figure 7. Saving a Copy
    Figure 7. Saving a Copy

    Saving Files in Photoshop

    We recommend that you save a copy of your Photoshop files that have been converted to sRGB and keep your originals as they are. The sRGB files should be saved as jpegs with Embed Profile ticked.