Qkano <snapper@xxxxxxxxxxxxxxxxxxx> writes: > A) Assume there was no cropping? > Well, it said a 4x5 camera > The aspect ratio should therefore be 1:1.25 > yet the two images presented have an aspect ratio of 1:1.6!!!! > This throws things a little before we start ;o) But, in fact, the claim of "no cropping" is an irrelevancy. So long as the two photos were really made on the same size film and enlarged the same amount, and so long as they show the points we need to measure (which they do), then cropping stuff off around the edges makes no difference. > > B) If the mountain peaks are really many miles away, relative > perspective on their various peaks should be preserved. > Treating the relative change in distance from the mountains as > negligible, the image on the right would have to have been made with > a longer focal length lens. Indeed, as long as the change in > distance from the mountains was negligible the ratio of the focal > length would be inversely proportional to the distance on film of > the two peaks. * On that basis alone the focal length of the lens > on the right should be ca 276mm "Change in distance is negligible" is a better way to put it than what I found. I was thinking of them as being "at infinity" in both cases; and that's only an approximation. Your formulation makes that explicit. > C) There is no evidence of convergenge in either the walls or tower > of the church. The caption does not say one way or another whether > the camera had any movements (tilt/shift). Assuming that the walls > and tower had parallel walls then these were "straight on" shots > therefore - film plane parallel to gable end of building - then the > centre of the photographs *should* represent thier "look at > points". All else being equal, not only would the shot on the right > have been taken from further away, it would also have been taken > from higher ground. > > That said, ignoring the inevitable parallax issues, and assuming the > answer was distance only in the horizontal plane, I reckon the shot > on the right was taken from 2.45 x the distance ... Of course, I > would need to check this ;o) The key point being it's a simple proporation. -- David Dyer-Bennet, <mailto:dd-b@xxxxxxxx>, <http://www.dd-b.net/dd-b/> RKBA: <http://noguns-nomoney.com/> <http://www.dd-b.net/carry/> Pics: <http://dd-b.lighthunters.net/> <http://www.dd-b.net/dd-b/SnapshotAlbum/> Dragaera/Steven Brust: <http://dragaera.info/>
