suggestions needed for undistorted interior mosaics

Discussion forum for techniques and issues relating to the creation of panoramic and/or "mosaic" images

Moderator: spamkiller

Post Reply
nathanoj
Posts: 175
Joined: Thu Nov 30, 2006 12:03 am
Location: Qld Australia
Contact:

suggestions needed for undistorted interior mosaics

Post by nathanoj » Sun Mar 27, 2011 8:39 am

For shooting architecture, and lacking a TS lens, I'm wondering the best technique of mosaic capture & stitching to achieve vert & horiz FOVs that exceed that captured in a single shot by say a 12mm rect lens, while maintaining straight lines and unstretched (as fas as possible) peripheries.
What is the best projection? What FOV is it best to remain within?

The Technical Data table for Max's recent Richmond Town Hall photo is informative, but is it possible, by not 'going too wide' to eliminate or minimise curvature in lines distant from the horizon?

I don't need to produce a large rez image, just see more ceiling or floor where it is warranted.

maxlyons
Posts: 3649
Joined: Fri Jun 20, 2003 8:55 pm
Location: USA
Contact:

Re: suggestions needed for undistorted interior mosaics

Post by maxlyons » Sun Mar 27, 2011 12:16 pm

nathanoj wrote:For shooting architecture, and lacking a TS lens, I'm wondering the best technique of mosaic capture & stitching to achieve vert & horiz FOVs that exceed that captured in a single shot by say a 12mm rect lens, while maintaining straight lines and unstretched (as fas as possible) peripheries. What is the best projection? What FOV is it best to remain within?
If you want to make sure that all straight lines in the scene appear as straight lines in the final image, then there is only one choice of projection: rectilinear. All of the others will, by definition, produce curved lines of some sort. This is an unavoidable, mathematical consequence of the way projections work. For example, cylindrical projections all produce curved horizontal lines above and below the horizon, while keeping vertical lines straight.

And, if you use rectilinear projection, then the images appear to stretch towards the edges. This, too, is an unavoidable, mathematical consequence of rectilinear projection. A 12mm lens (on a "full-frame" camera) produces an image with a field of view of about 112 degrees (see the Angular Field of View calculator on this page). And, that produces an image that is pretty close to the limit of what I'd consider to be an "acceptable" amount of stretching, before the image stretching appears excessive. Of course, different people have different opinions on this, and you may be happy with a rectilinear image with 120 or 130 degree FOV. Your call.

PTAssembler offers numerous other projections that may be useful in some circumstances. For example, the Trans Merc Rectilinear, Compressed Rectilinear and Squeezed Rectilinear projections all offer straight horizontal and vertical lines with less edge stretching than rectilinear. However, the tradeoff is that some other lines (diagonal) will not be rendered as straight in these projections. Unfortunately, there is no "free lunch"...in order to gain control over the stretching at the edges, you have to lose something else (straight diagonal lines).

Max

nathanoj
Posts: 175
Joined: Thu Nov 30, 2006 12:03 am
Location: Qld Australia
Contact:

Re: suggestions needed for undistorted interior mosaics

Post by nathanoj » Sun Mar 27, 2011 5:25 pm

Thanks for that succinct summary Max. I've been away from panos for a while and wondered what the latest wisdom on this was.
No magic bullet and no free lunch! :-D
But now to test what I CAN get away with.

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest