Parts of the way Aperture (3.2.4 on SL) uses screens seems to depend on what mode you are in, (browers, viewer, combined) what mode you are in when you went full screen, what the setting for Secondary display is, and I suspect other things previously thought only to affect the flavour of pizza.
I have had two situations that I wanted to use 3 screens:
Scenario 1. I want to use two screens to run aperture, and one to run keynote. Can’t do that unless I keep keynote on top of an aperture screen.
Scenario 2. I want a browser on screen 1, my keyword HUD and my metadata inspector on screen 2 and my expanded selections on screen 3.
I finally got 3 monitors hooked up again. And Aperture seems to do the Right Thing.
With Main in browser mode, Alternate mode shows the primary selected image on one monitor, as many selected on the other monitor as will fit.
In span mode, selected images alternate on the two secondary monitors. (It is not clever enough to take advantage of screen space if one is in landscape mode, and one is in portrait.
Filmstrip mode on primary isn’t useful. In Alternate one monitor has the primary image, then both the viewer in filmstrip, and the other secondary viewer have the same images. In Span mode whatever is in the viewer is on one monitor, and the other monitor is also full of images.
In mirror mode all 3 viewing areas have the same selection.
Hitting full screen mode turns leaves one secondary blank, and does NOT move the images that were on it to the one remaining on.
Scenario 1: Answer is to put in mirror mode, and put Keynote on top of one of the mirrors. Clicking on any one monitor only brings that window to foreground. If you click on the icon in the dock however all come forward.
Scenario 2: Use a portait monitor as my main screen. Put the keyword HUD on top of the lower half of the Inspector panel on left. You can put the HUD version of the inspector over the panel version if you want a darker environment.
Or you can have the inspector panel and the inspector HUD set to different views at the same time: convienient if you wan to check metadata and make adjustments at the same time.
My approach is to create a stretched work space across two and a quarter screens and set Aperture to split view, (using option W, then Shift W) I set the browser on the right side and put it in grid view mode. I then adjust the browser section of the split to cover just the right screen and the full image of the selected image to cover just the center. The quarter screen on the left is for the inspector pallet. I often use the HUD to split the inspector panels as you suggest. You can have any third program you want open on the third screen or 3/4 screen in this case. I use a Wacom Intuos 5 touch tablet for navigation and adjustments. It is propped on an angle from a keyboard tray to take the strain off of my wrist during long sessions.
See the image: http://www.johnwaugh.com/Work_Station.jpg
John Waugh, Photographic Images • Apple Certified Trainer• Sport Action Lifestyle Photography