Hello,
 
I have flown overseas and am photographing buildings extensively to create models for a video production.  It will be my first project using imagemodeler and, silly me, I left the country without double-checking some importants points.  I will be using imagemodeler v2.1.  Any answers would be GREATLY appreciated as my manuals are very unavailable.
 
My questions are:
 
1.  Must I use the same focal length while photographing different views of any given building?
 
2.  What is the recommended minimum focal length I should use when photographing the building?  I am using a 17-35mm rectilinear zoom lens on a 35mm SLR stills camera.  The lens has almost zero barrel distortion, but of course, at 17mm, does distort the subject at the outer edges of the photo in relation to my distance to it (but the distortion is rectilinear, not curvilinear, in case that matters).  I am wondering if this distortion may cause problems when trying to generate 3D co-ordinates.  The streets here are narrow and I can't photograph everything with a longer focal length.
 
3.  Can I photograph the buildings, then move in closer for details or close-ups of parts of the subject which may have been occluded in all of the other photographs?  Will this generate good results or must all the photographs have been taken at a similar distance to the subject?
 
Thank you very much!
k

Hello,
 
1) Same focal length helps to constrain your calibration, but its not necessary.
I would say keep the same focal length, if you can keep the same distance to your building while moving around.
 
2) Distortion could be a problem (focal length should not).
Solutions (if strong distortion):
- un-distort your photographs with dedicated software
- re-create wide angle photographs with stitcher using several photographs stitched together (see Valbonne Church's example)
 
3) Generally close-ups are difficult to add in the calibration. I mean a close-up of one window will be difficult to calibrate with photographs representing the whole building.
If you make close-ups, try to keep some building corners in your photograph; should be possible with your lens.
 
Hope it helps,
 
Stef