How to make a presentation screenfilling with powerbook Pro 17 inch screen

Question

I made a presentation with photographs. Now I want it to play filling up the screen. My pics are the original 2x3 format (six by four on 300 dpi), it does fill up in height, but not in width.
I have two black borders on the side of my slides. How can I avoid that?
Will it play frame filling on a second display?
Is it because my laptop has a 17 inch screen set on 1650 display resolution?
I tried to change the resolution in keynotes itself, but it pushes the pics down so they appear wider and out of proportion if I go to stretched...
Extremely annoying. Can anyone help me out????
The slides are all on a blank black background, no masks...

Answer 1

Catherine, the "odd" ratio of 16:10 is used by Apple because it closely matches the 16:9 ratio of high-definition video.
Resolution is really not the issue here, it is simply that photos with the aspect ratio you have won't fit fully in the "frame" of the monitor, just as if you were trying to fit them in a physical frame without a matte. If you think of the extra black space as essentially the matte of the frame, that might help to clarify the issue.
I would, however, recommend that you consider downsizing the resolution of your photos, as 4200 pixels is way bigger than any display can show without automatically downsizing, and doing the reduction yourself will a) give you better control over the final appearance, and b) should really help with the performance of the presentation (since Keynote does not have to do the reduction itself on-the-fly). The photos should be reduced such that their height in pixels is no more than the height of your slides. You can find your slide height by looking at the Document Inspector.
You don't say if the presentation will be viewed on your computer, or projected. If it is to be viewed on your laptop, then I would recommend setting your slides to be the actual size in pixels of your laptop screen. Once you've done this, scale your photos in Photoshop or a similar application to be no larger than the dimensions of the slide. In this way, you will best preserve the quality of the images.
If the presentation will be projected, your options are more limited, since the quality of the final display is largely a matter of the resolution (and quality) of the projector. Generally, projectors have a resolution of either 1024 X 768, or even 800 X 600, and so are likely to be much lower resolution than your laptop screen. In this case, the ideal solution is to determine the "native" resolution of the projector you will use, and set your slide size to that (changing your photos accordingly).