Changing the colours of photographs in your InDesign project requires Photoshop, right? Not necessarily. If the photo is black and white and saved in grayscale mode in a compatible format, you can tint it directly in InDesign. You can even assign it two colours for an attractive duotone.
A duotone is an image with two colours or tones, effectively a grayscale image, but more accurately one that substitutes a colour for black and another colour for white or negative space. For example, sepia, a popular effect wherein the main ink is a shade of brown atop a yellowed or off-white background colour, is a duotone. While there are varying definitions for the term that have evolved over time, the technique I demonstrate below reflects this interpretation.
Tinting photos in InDesign is easier and faster than working in Photoshop, and it offers more flexibility and freedom for experimentation and adjustment. While tinting in Photoshop gives you superior control because you can use Curves to alter which shades of gray are replaced by which colour, tinting in InDesign is a simple duotone process to replace both black (ink) and white (background) with different colours. Here are a few quick steps to get you started. Note that while I'm demonstrating this technique with Adobe CS4, you can accomplish the same thing with previous versions of the software.
Prepare the image. First, you need to use Photoshop to convert your colour photo to grayscale (if it isn't already), and save it in a format that supports grayscale mode -- a TIFF, JPEG, or PNG will work. To convert a colour photo to grayscale, use the Image->Mode->Grayscale command and then save the image.
Place the image. With a document open in InDesign, choose File->Place, load the image, and click on an empty area of the document page or pasteboard to drop it into the page.
Tint the image. Make sure the InDesign Swatches panel is visible (if it's not, choose Window->Swatches). Use the Selection tool (the black arrow) to select the image's container. This is the frame that contains the image, not the image itself. On the Swatches panel, make sure the fill colour is the foreground swatch rather than the stroke colour. If it isn't, click the fill swatch to bring it forward.
Next, click a colour swatch on the Swatches panel or mix up a new colour in the Color panel. The background of the image frame will change colour to match that colour -- and so will the white areas of the photo because InDesign treats white in grayscale images as transparent. Thus, when you give the image frame a background colour, it shines through the white in the image.
Note: If nothing happened in this step, your image probably isn't saved as a genuine grayscale mode TIFF, JPEG, or PNG. Bring the image back into Photoshop and check its mode on the Image->Mode menu and make the appropriate changes.
Add a second colour. Now that your image is tinted with a single colour, you don't have to stop there. You can go ahead and add a second colour for a distinctive effect. To do that, switch to the Direct Selection tool (the white arrow) and click on the image inside the frame. You'll see the image bounding box go from blue (the layer colour) to brown to indicate that you're editing the image itself, not the frame. Now, pick another fill colour from the Swatches or Color panels. Whatever colour you pick will replace the black and gray values -- all shades except pure white.
Create a sepia tone. To achieve a sepia effect, start with a background (frame fill) CMYK color (from InDesign's Color panel) of C: 2, M: 8, Y: 33, K: 3, and a foreground (image) color of C: 35, M: 56, Y: 61, K: 53.
You might be wondering: If you must prep grayscale images in Photoshop, why not just do the tinting there, too? You could, but then you'd have to save the image in those colours. The above technique lets you simply save a single grayscale image while giving you the freedom to tint, adjust, and retint it as often as you like, with as many copies on the page as you like, all with only one linked image file to manage.