Reader Doug McGowan is interested in creating instructional slideshows. He writes:
I have some information that I’d like to present to a group via a slideshow that they’ll watch on their computers. I have the pictures I need in iPhoto but I can’t find a way to annotate them. Is it possible?
Not in an effective way. The Ken Burns and Classic slideshow themes let you display captions. And although you could do this by adding some text to each image’s Description field within its Info window and then choosing to display the description as a caption, iPhoto will cut off long strings of text rather than wrap them to a new line. Plus, there’s no way to add a background shape (a colored rectangle, for example) to help set off the text.
If I were doing this (and I have on a few occasions), I’d turn instead to Apple’s Keynote in the following way.
Launch Keynote and from the theme chooser select the White theme and click Choose. With the latest version of Keynote, the Format button at the top of the window should be highlighted. In the area below this button click on Change Master and choose the empty slide at the bottom right of the list. You should now have a single empty slide.

Add images via Keynote’s Media browser.
Click on the Media button at the top of the window and in the Photos tab, navigate to the first image you want to use and click on it. It will be added to your slide. Now click on the Text button at the top of the window to add a text box. Enter the text you wish to use, configure its font and size, and drag it to where you’d like the caption to appear. With the text selected make sure the Style tab is chosen in the sidebar to the right and choose Color Fill or Gradient Fill from the Fill area. Choose an appropriate fill to go with your text—I might use white text on a gradient background that moves from gray to black.
Hold down the Option key and in the Slides thumbnails area, drag the first slide down to make a copy of it. Click on that slide’s image and press the Delete key to remove the image (but keep the caption). Click the Media button again to add a different image. Press Shift-Command-B to send that image to the back so that the caption is exposed. Triple-click on the caption to select all its text and enter the caption you want for that slide.
Repeat this process for additional slides. Then select all the slides and click on the Automate button near the top-right of the Keynote window. Click on Add an Effect and choose a tasteful transition (Dissolve is always a safe bet).

Export your work as a QuickTime movie.
Finally, choose File > Export To > QuickTime. In the Export Your Presentation sheet that results, don’t change the Self-Playing setting in the Playback pop-up menu, choose how long each slide will play, select an output format (720p, 1080p, or Custom), and click Next. In the next window name your movie, choose a place to save it to, and click Export. In a short while your slideshow will be saved as an MPEG-4 movie, ready for you to share with the group.