When you launch Keynote and choose a theme for your new presentation -- or apply a new theme to an existing presentation, you can change the Slide Size of the presentation.
Now the Slide Size is actually almost the same as the resolution of your presentation -- and is related to the resolution capabilities of your monitor display and projector. This is not as geeky as it sounds -- just remember that the most common and safe resolution for all new projectors is 1024 x 768 pixels -- so if you never bother changing the slide size, Keynote will continue creating your presentations in this resolution. In fact, Keynote defaults to 1024 x 768 pixels -- just stay with the defaults until you get a little more Keynote savvy.
Older projectors worked at only 800 x 600 pixels, and most of the higher end projectors can support much higher resolutions. Of course, if you want to choose a Slide Size that's different than 1024 x 768, you must have a compelling reason to do that -- maybe you want to use a wide-screen aspect, or you have been asked to use a different slide size.
You can choose your Slide Size in the drop down box of the same name that you can see in Figure 1.
Figure 1: Slide Size in Keynote
As you can see in Figure 1 above, Keynote provides you with five slide sizes for this particular theme (Harmony) -- on the other hand, look at Figure 2 and you'll find that this theme (Blackboard) has only two slide sizes. This makes it obvious that all themes don't have all slide sizes.
Figure 2: Slide Size in Keynote
You'll find a more detailed explanation of slide sizes in Keynote on the Apple site.
Labels: apple, basics, geetesh bajaj, keynote, resolution, slide size, theme