same photo, differences in prints - why?

Factual Questions
1

Here are two slightly different images of the same shot:

http://www.flickr.com/photos/99115850@N00/sets/72157606984760907/detail/

They must be the same shot because the water ripples are identical and the flags are also identical.

But what should be straight lines are curved differently in the images. The clearest example of this is on the tall building on the right (Tribune Tower), where its left edge against the sky is clearly bowed outward in image 42_1024x768, but bowed slightly inward in image 127_1024x768. Other differing curvatures can be seen on the bridge and the river embankment.

Ι know very little about photography, but when I see something bowed outward, I think “a slight fish-eye-lens-type effect”. But to me that’s too simple to account for the situation here. And it can’t be the camera because, as I stated above, both images are from one shot.

My main question is this: since this must be one shot, how did the different curvatures arise? The same negative scanned on two different machines before uploading? Are any of my thoughts correct?

There are other small differences. There’s (scan?) blurring at the left edge of 127_1024x768. Both images are supposed to be 1024x768, but 127_1024x768 is only 1024x762. And in 127_1024x768 there’s more sky visible above the spire on the tall building (Wrigley Building) on the left.

2

I don’t think they’re from the same shot. In #42, you can see some windows that were not in #127 along the far right edge.

My guess is that the photog took a picture from a tripod, then adjusted the angle at which the camera was pointed, swiveling it up/down a bit with regard to the horizon.

If you look up “perspective control” or “perspective shift” lenses, it will give you a better idea of why architectural photography is a headache: basically you need to get the camera up to the midpoint of the building you’re photographing or else it will distort badly…or you can get a special lens that imitates what view cameras can do, altering the position of the lens in relation to the film plane.

3

The two shots have different magnifications. If at the distance between two different features in the images (in pixels), it is not the same. I don’t think the images are the same shot.

4

Just a thought…cross your eyes until the two images become one…if the images are different mags or perspectives, the combined image will look 3-d.

5

Photoshop CS includes a filter for correcting lens distortions. The first shot is uncorrected, the second is corrected.

6

If the shots are in fact from the same exposure, then what Squink said. I don’t have this filter, but I often correct such shots of my own, manually, in PhotoShop.