I had to get a 'new' image processing program (GIMP, while possibly the *worst* name ever, is available free at
http://www.gimp.org/) in order to submit a paper to PLoS, and it does some things that ImageJ does not- one thing in particular is a 'perspective tool'.
Recall that, given a fixed 35mm image format, lenses with a focal length equal to 50 mm provide images with perspective matching human vision, while lenses with shorter focal lengths provide exaggerated perspective and lenses longer than 50mm reduce the perspective.
Here's an example: I used a 15mm lens to take a photo of Cleveland's tallest building, the Key Tower with 57 stories and almost 1000 feet tall:
[PLAIN]http://img836.imageshack.us/img836/9895/dsc70402.jpg
The short focal length let's me get the whole building in the frame, but because of the increased perspective distortion, the building appears to recede rapidly into the distance, much more that it appears when looking at the building by eye. Of course, you can't fit the whole building on your retina unless you stand much further away from the building than I did here, which is why I used a wide angle lens to begin with.
Using the perspective tool, I can mimic the effect of using a tilt-shift (or long focal length) lens- parallel lines remain parallel:
[PLAIN]http://img546.imageshack.us/img546/3540/dsc70401.jpg
This image is impossible to obtain 'naturally'- in order to flatten the perspective this much by using a telephoto, I would have to stand so far back that the view would be obstructed by other buildings. Although Canon makes a 17mm tilt-shift lens (http://www.luminous-landscape.com/reviews/lenses/canon-17ts.shtml), I'm not sure it could move enough to accommodate this building. A telecentric lens would need to have a front element 1000 feet in diameter to take this image.
An important reason I was able to perform this manipulation is that the lens has no distortion- straight lines remain straight. That's a major reason I got this particular wide angle lens (Nikkor 15mm f/3.5) instead of other wide angle lenses.
I like the result- the building looks normal and different at the same time. I'll be on the lookout for other opportunities to try this out- lighthouses could be very compelling subjects, for example. The Statue of Liberty would be *excellent* since it's so iconic, but I don't know when I'll be in the city next.
