An English post for once. I just got back from the lab, getting y freshly developed Nikon F4 Negatives in Black and White. Or at least inverted.
But I have no scanner here. Now what? Sure, I can wait, but I still want to see how they look.
Well, que Photo Booth. With the standard X-Ray filter, you get a grayscale view of the world, but just a little bit inverted.

So all we need is a backlight that serves as a backdrop for the negatives. In this case I used my trusty iPhone with one of the gazzilion free Light apps, and voila, an instant negative / positive viewer.

There also are extra effects (More iChat Effects) that show a colored negative, but these are not really that effect. See for yourself:

Still, for those quick grayscale views, it’s perfect!
Of Course, if you could set the iSight to manual exposure, it would be easier, but we can’t have all, can we? :)