Does a photo give spatial information (the nose job)?

[AlfSollund]

I think our difference now simply boils down to semantics.  I define spatial information less narrowly.  Any information in a photograph (perspective for example) which provides some clues that allow one to make an informed estimate (guess) about the relative position and/or size of the 3D objects, I would describe as spatial information.  Clearly it is not always guaranteed to be correct information, and certainly one can have photos which contain no spatial information (even by this looser definition). 

Yes, agree. And thats why in my first post wrote "The information can be used to guess about spatial, but no information can be derived for sure. Its no way of knowing the relative spatial positions to objects in a photo, or even if they are spatial." So I would have said "information to create spatial models" instead of "spatial information". But again, this might be to formal. It boils down to as you say semantics.

This is in agreement with what bill t., BJL, Ellis Vener, Hjulenissen, yourself and perhaps others have said here. Thanks to all.

I have always loved fishing.  As a very young boy I learned a trick when being photographed with my catch.  Hold the fish at arms length straight out in front of my body, and close to the camera.  At first glance it makes the fish look much bigger, but it doesn't fool too many viewers.  Which brings us back to the original theme of this thread.  It is this same "trick" that makes a nose look much bigger in proportion to the face when the camera is positioned quite close.

Totally OT, but you should look my site http://flyalf.com/. On the right hand side there are links to some of my fishing trips  .

Check out this  (no, not myself in the pic):
http://www.flickr.com/photos/25078442@N05/4922442239/in/set-72157624795885356

[Wayne Fox]

So how will we do this if I take a photo of a photo? There is only one object in this photo, and that is a (near) 2-D object. namely the photo i photograph. Secondly there are methods to guess the actual size, but not possible to know for sure.

mmm, I didn't see some of this in your original post, you didn't say anything about a photo of a photo or other qualifications.  I assume spatial information has to do with where things exist in the 3 dimensional reality of a scene in relationship to each other.  If you have specific information about the objects in the photograph it seems pretty straightforward to make measurements of the items in the photograph itself and derive some spacial information.  If there were 3 different balls in the scene ... a baseball, a football and a basketball, and they were all at different distances from the camera, you could calculate where they were in relation to each other by measuring the actual size.  Using information derived from this it seems you could calculate information about other objects in the scene where you don't know the actual size. Not sure how accurately, maybe sometimes very accurate and other times more like an educated guess.

But then I'm no scientist or math whiz, and if someone actually  asked me to do something like this, even my curiosity wouldn't be tempted by this problem and I'd find some excuse to not do it.