posterization

A couple of ideas:

iMovie will take your 10 megapixel (or whatever) photo and convert it to either 1920x1080, 960x540, 640x480, etc. based on your aspect ratio and your export settings.

You may get better results if you use photoshop or Lightroom to do the initial reduction to, say, 1920x1080. You will have a lot more control.

But I am not a photographer, so others may have a better idea.

Again, I have no expertise in this area, but you might try:

In System Preferences, do you have a calibrated display? Can you switch back to the default display and see if it makes a difference? (It should not, but worth a try)

In System Preferences/Display, are your Colors set to Millions?
Sorry to be so obvious but that is my last try. Good luck, there are others here who may be more knowledgeable.

What is the file format of the source files? In a case like this I would be using TIF or PNG. What is the bit-depth? 8-bits are all you get, so if you are at 16-bit, convert before bringing them into iMovie. What color space are you using? I would suggest sRGB for video purposes. Finally, a DVD movie will never be as rich or have the resolution of an actual image/print. You could use a program such as Adobe After Effects to create slideshows using the animation codec and those are quite nice. Quite large as well. If memory serves a 10-minute slideshow created a 13GB file.

Mike

And your friend uses these same images on a calibrated monitor and they look fine? Black & White gradients are notoriously hard to PRINT which has a wider range than a TV display (and different than a computer monitor). While FCE will offer other benefits (I am pretty sure you can key-frame and edit key-frames), I doubt you will get any better image results. I might look into something like Fotomagico ( http://www.boinx.com/fotomagico/overview/) which will simply use a different rendering engine as opposed to iMovie or FCE (either of which were developed as DV editors). Other than that, for the highest quality slideshow you are looking at Adobe After Effects.... or farming out the slideshow to someone with After Effects. Simple slideshow with images already prepared could be done in less than a few hours (probably less than an hour). Might be worth looking into if this is a demo DVD.

Mike

Now you lost me a bit. Going pear shaped would be an indication of square (computer) vs rectangular (TV) pixels, a bit different issue than posterization. You also point out that the movies look OK in QuickTime... did you use QTPro to create a slideshow? And then bring this slideshow into iMovie? In other words, what is your exact workflow and how does it differ from your friends?

And we may also want to back up a step. Strictly speaking, I am not sure you would be happy with FCE from an image quality standpoint. If there are other things you are looking to accomplish with an editor and iMovie is holding you back, then I wouldn't hesitate to say jump to FCE. I took a quick peak at the website and personally, I think you will be better of just biting the bullet and getting Adobe After Effects. Here is a quick tutorial with After Effects and a slideshow:

http://library.creativecow.net/articles/kramer_andrew/slideshows.php

And again, this rendering engine will be superior to even FCP. I have two other quick suggestions. One, I wouldn't use a cross-dissolve transition between slides. I personally wouldn't use any but a cross-dissolve is very hard to compress efficiently and will almost always break up when compressed the web. The 2nd would be to add a slight key-frame to each image. Even if it's minimal, slight motion helps eliminate a lot of artifacts presented when using motion picture platform (video slideshow) with still images.

Mike

After Effects is best described as Photoshop for video: http://en.wikipedia.org/wiki/AdobeAfterEffects.
http://www.adobe.com/products/aftereffects/

Would it be overkill for slideshows. Sure. But no more so than Photoshop is for an image!!!! Meaning, did you use Photoshop 20-years ago?! But now we can't live without it. I have only started to learn After Effects... but it's pretty cool. A professional tool for professional results.

In what format are you capturing your screencast (resolution & codec)? And then you export this into a high quality QT format but is it going through an additional layer of compression/conversion (QT offers a lot options). And then you bring this into iMovie which is expecting a specific resolution and if that isn't there, then iMovie will convert as it can. Your screencast is likely captured at a different resolution and frame rate than what iMovie needs to work with and that will cause a loss of quality. It's like outputting a web JPEG, but then going back to the web JPEG version, making modifications and then wanting a print: two different mediums. In this case we have a screencast vs DV editing (iMovie) where DV has a specific aspect ratio/pixel dimensions and frame rate that may differ from the screen cast.

The tutorial will show you key frames in After Effects. In iMovie, you have "Ken Burns" effects which are simple keyframes.

Mike

And this is where my lack of experience using the software comes into play! But maybe I can point you in the right direction... for anything you want to edit, you want to start with as high a quality as possible (the RAW file if you will). Outputting from your screen capture software is one place to start. If you can output at a higher quality, I would. H.264 is a very compressed codec. Great for delivery, not so great for future editing. Keep in mind that the larger the file size, the better the video (TIF vs JPEG). iMovie (or FCE) only works with certain dimensions, anything outside of these dimensions means something is getting re-sampled. The LAST thing in the chain would be to export the web quality video (which iMovie can do for you).

I am in the US so I am using NTSC. For me, this means a 4:3 aspect ratio is 640x480 square pixels @ 30 frames per second preferably in the DV codec (not MPEG or h.264) is what I would want to bring into iMovie. The more closely I can match that, the better things will look in (and out of) iMovie. I really think it's what you are giving iMovie that is the weakest link in the chain at this point. And FCE won't help with that.

All of that said, if iMovie is producing acceptable results, it really becomes a matter of ROI, cost benefit analysis. I think the Adobe suite has products more in line with what you are trying to do but is the learning curve/expense worth it? Heck, I want a new D3x... but that ain't going happen. I will trudge along with my D300.