Curved buildings and distorted perspective in panoramas

I was browsing through the 'technique' page and came across a problem I've been having.

Namely, when i take panoramics (or mosaics) and stitch them together afterwards, buildings (such as kings chapel) seem curved and the perspective is distorted. Images posted here have managed to compensate for this effect somehow and hoped someone could share the secret! I use a Canon ixus IIs, (my first camera) and stitch using 'Canon PhotoStich'. The only other software i have is 'Photodeluxe home edition', the forerunner to PS I believe.

If your images are aligned well (no significant seams), then I believe the distortion you speak of is due to the type of panoramic image projection.

If your software supports it, use a "rectilinear projection" as this maintains straight horizontal lines. Most software programs default to a "cylindrical projection" since this can span any angle of view (up to 360deg even), while the rectilinear projection is not advisable beyond what angle you could get with the widest lens. If you cannot do this with the software you have, try PTAssembler as this is one of the most feature-rich stitching programs out there. It may not be the easiest to use (although this has improved dramatically), this comes increased power and flexibility. Even though it has a one-click "autostitch" feature, I always recommend manually selecting each control point as this can produce truly seamless stitches
(assuming the nodal point of your camera lens remains the same for all shots).

There's also a new article up on using photo stitching software which discusses blending the seams between photos and selecting control points.

Hope this gets you started.